OPHTHALMOS

 

 

AN INVESTIGATION OF THE EYE IN ANTIQUITY

 

 

 

 CLAYTON G. SCANLON

XAVIER UNIVERSITY

HAB SENIOR THESIS

 

 

 

 

 

IN MEMORIAM

 

HAROLD JOHN SCANLON, SR

Whose intense appreciation for the classics and traumatic eye injury fated this investigation many years ago.

 

ABSTRACT

                It is clear from my cursory study of the eye in antiquity that it was surrounded in mystery.  This was primarily founded in the eye’s elusive anatomy and physiology, which has baffled investigators since the beginning of anatomical reflection and yielded numerous theories from some of the world’s most famous minds.  It is also founded in the eye’s enigmatic identity, in a very literal sense, as a window into one’s soul.  The eye harnessed a certain power as an external extension of the mind, and this power is discernible in the early language and concepts used to explain ocular mechanisms.

            The main goal of this thesis is to investigate and explain some early theories of eyesight, tracing the eye’s anatomical and physiological identity from roughly 600 B.C. to 200 A.D.  It is evident that the eye commanded a great deal of respect, as reflected by the intense philosophical and scientific contributions of ancient scholars.  The work of the ancients and their elevated respect for the eye is a crucial element to the sometimes unexplainable inherited importance that humans place on their eyes today.

 

 

 

 

 

 

  

OPHTHALMOS

 

An Investigation of the Eye in Antiquity

 

 

 

CLAYTON G. SCANLON

Xavier University

HAB Senior Thesis, Spring 2004

 

 

Under the direction of:

 

Frederick Benda, S.J.

Department of Classics, Xavier University

 

Dr. Lisa Close-Jacob

Assistant Professor, Department of Biology, Xavier University

 

Dr. Edmund Cueva

Chair/Associate Professor, Department of Classics, Xavier University

 

Dr. Arthur Dewey

Professor, Department of Theology, Xavier University

 

 

 

Defended April 26, 2004

Schott Hall, Xavier University

CONTENTS

 

 

INTRODUCTION……………………………………………………………..1

 

CHAPTER ONE: PHILSOPHY LEADS SPECULATION…………………. .5

 

CHAPTER TWO: A MORE EMPIRICAL APPROACH…………………….17

 

CHAPTER THREE: FROM GREECE TO ROME AND BEYOND………...35

 

CONCLUSION………………………………………………………………..48

 

APPENDIX: FIGURES………………………………………………………..50

 

WORKS CITED……………………………………………………………….60

 

REFERENCES………………………………………………………………...62

 

 

 

 

 

 

 

                                                           

 

 

“The bodily well-being of an individual is not only determined by the untroubled function of the eyes, but his existence, the prospect of fighting for life determined directly by the degree of efficiency of his eyes.”

 

 

-Hugo Magnus

 

 

 

 

 

 

 

 

LIST OF FIGURES

 

FIGURE ONE:  ANCIENT VS. MODERN INTERPRETATION OF SIGHT

 

FIRGURE TWO:  EMPEDOCLEAN SPECULATION

 

FIGURE THREE:  TWO POSSIBLE DEMOCRITEAN THEORIES

 

FIGURE FOUR:  THE EYE ACCORDING TO DEMOCRITUS

 

FIGURE FIVE:  THE EYE ACCORDING TO HIPPOCRATES AND ARISTOTLE

 

FIGURE SIX:  PLATO’S THEORY OF VISUAL TRANSMISSION

 

FIGURE SEVEN:  THE EYE ACCORDING TO CELSUS

 

FIGURE EIGHT:  THE EYE ACCORDING TO RUFUS

 

FIGURE NINE:  THE EYE ACCORDING TO GALEN

 

FIGURE TEN:  MODERN INTERPRETATION OF THE EYE

 

 

 

 

 

 

INTRODUCTION

 

Speculation about the eyes and their function is most likely as old as mankind.  Since the inception of written records there have been theories posited concerning the nature of sight.  This poses the argument that ophthalmology has the earliest origins of the medical disciplines.[1]  Over time, the eye adopted an identity of importance and respect, which fueled many scholars to uncover its mechanisms.  The result theories of antiquity are extremely interesting and show supple minds practicing keen observation.  This thesis will attempt to explain and clarify some of those early theories of the eye and its function, and that analysis of the evolution of the eye’s structure and function leads to a greater awareness and understanding of the value that is placed on sight.  Explanation of some of these early theories will hopefully lead the reader to enhance their own (perhaps unconscious) appreciation for eyesight.        

This thesis will focus on the eye from an anatomical and physiological perspective.  This approach will incorporate the necessary fields of knowledge and themes that gave the eyes importance in antiquity.  The time frame of the material presented here is roughly 600 B.C to 200 A.D.  Although this period was by no means the beginning of ocular thought and the standardization of the significance of the eyes, I believe it to be highly reflective of the development of the identity of the eyes.  This time period will be divided by two key transitions,  one marking the movement of ocular thought from a primarily philosophical approach to a more scientific approach;  the other marking a geographic/cultural shift as empirical modes were furthered in Alexandria and the ocular maxims of the Greeks were adopted by the Romans.  It is important to remember, however, that despite these divisions, philosophy, anatomy, psychology, and sometimes magic have played interrelated roles in the process of establishing theories, no matter what time period is analyzed.  The divisions used here, however, are conducive for efficiently including the thoughts of a number of ancient scholars.  Within these groupings, the format will be similar.  The main anatomical and physiological thoughts and ideas of the most prominent contributors of each period will be discussed, in order to further clarify and at times elaborate upon the past work of others.  Thus, a distinct evolution of the complex identity of the eye will be seen from a scientific perspective.

* * *

There is an abundance of literary evidence showing the importance of the eye.  For example, Matthew 6:22-23 describes the eye as the “lamp of the body.”  This passage gives a certain moral character to the eyes as it goes on to correlate “whole” or good eyes with inner light and evil eyes with inner darkness.  A brief look at the emission theory shows the pertinence and strength of the eye motif.  Analysis of even older texts of antiquity (such as drama and poetry) shows a similar bond between the eye and morality.  The eye is portrayed as a messenger to and from the soul and has a direct link with the psyche of its beholder.  This leads one to take a great interest in the eye as a conduit for bi-directional light both in a physical and spiritual manner, and to wonder if anatomical concepts of the eye parallel this notion.  Figure 1 is a representation of the relationship that demands investigation.  I will show that highly complex empirical theories and equally complex status levels for the eye follow from that simple sketch.  As mentioned above, reflection concerning the eyes and vision has been practiced since man’s origins.  Indeed, literature on the subject affirms this notion.  Andersen claims in the preface to The Eye and its diseases in antiquity, “From ancient times the eye has not only been an organ of vision but a symbol of importance in the cults of peoples.”[2]  Arrington also notes that “even prehistoric man seems to have recognized the immeasurable preciousness of sight and to have extended mystical powers to the eye”.[3]  As early as 1900 B.C. the Egyptians were recording medical information on papyri including eye diseases.  Mexican statuary dating about 1200-1519 B.C. shows eye abnormalities as well as attempts at treatment.  Similar to the eyes’ role in Biblical morality, magical and supernatural characteristics have accompanied attempts to reveal the mechanisms of the organs of sight.  Egyptian coffins from the 17th dynasty were adorned with the “two mystic eyes.”[4]  Statues of mighty gods from Mesopotamia around the 4th-3rd millenium B.C. were depicted with enormous eyes, a clear manifestation of a belief that eyes had a relationship with both powers of the body and the mind.[5]  Beliefs still common in parts of the world today related to the Evil Eye have their origins in ancient cultures as well.  

              The eye sits at a variety of important thresholds.   In terms of physiologic vision, the eye sits at the threshold of the external and the internal, accommodating the conversion of energies and the activation of hormones.[6]  The eye also sits at the threshold of the physical and the intangible, the place where an objectified form becomes subject to the vast labyrinth of our perception.  The eye is also common ground for voluntary and involuntary actions.  One can “turn off” the sense of sight at will, but constriction and dilation of the pupil, or blinking at the occasional airborne impediment or distraction is inevitable given certain environmental stimuli.  And finally, simply describing how the eyes work means incorporating the principles of biology, biochemistry, and physics.  These thresholds go beyond merely describing the way the eye scientifically functions.  It is true that natural science succeeds at communicating part of the eyes’ function, but what about other aspects of vision?  Just as there have been substantial scientific contributions to eye function, other (perhaps unexpected) fields have assisted in giving us information about sight.  Philosophy and psychology are used to explain why we “see” things a certain way.  There is not just the eye but also the “mind’s eye” that is so commonly referred to.  Theology also uses the eye to communicate its maxims. Since the intense contributions of both scientists and humanitarian thinkers had their origins in antiquity,  any investigation into the nature and history of the eye requires familiarity with a broad range of disciplines.  When these thresholds that find themselves seated in the eye are melded together, the result is that the eye itself becomes a physical symbol incorporating knowledge that reflects the human experience.  Beginning with the ancient scholars who expended great efforts to understand eyesight, discoveries and  contributions to ocular mechanisms down through the centuries reflect the breadth of human experience, and is at least partially responsible for the importance our society places on vision.  Individually this is also responsible for the intense value we place on our eyes, sometimes for reasons that we cannot logically explain.  It is these transformations, realizations, relationships, and enhanced appreciation for the eyes that I hope the reader can extract from the following thesis.

              The mystery of the eyes felt by the scholars who pondered their mechanisms and by the commoners who were wary of the power of gazes elicited respect, admiration, caution, frustration, and indeed fear.  The eyes have a relationship with their beholders different from any other organ of the body, and this timeless relationship has yielded an immense amount of speculation and knowledge to which we are highly indebted.

 

 

 

CHAPTER I

 

PHILOSOPHY LEADS SPECULATION

 

 

            The first time period discussed falls between the work of Thales of Miletus, around 600 B.C, and the inception of the Hippocratics, roughly around 450 B.C.  Thales was an important milestone as he began the work of the natural philosophers and the more ordered speculation on the function of human processes.  Indeed, as Solmsen commented, “the first and fundamental theories regarding the composition of tissues were put forward not by the Hippocratic physicians (to whom it never occurred to ‘wonder’ about them) but by philosophical physicists.”[7]  Before Thales, ophthalmic thought was certainly prominent, but in very different ways.  One could make the argument that ophthalmology is the oldest of the medical specialties, and this claim is certainly applicable to Greek culture.[8]  In very early times, eye specialists made their way into Greek mythology.  The first eye practitioner documented in mythology was Apollo, descending from Olympus to soothe the afflicted.[9]  As other figures such as Pallas Athene also became affiliated with medicinal powers of the eye, ophthalmology became further linked with Greek religion.  As this trend continued, it became more the jurisdiction of the priests.  Any attempts to cure pathologies had to be mediated by priests since deities were involved.  Over time, however, the priests began to compile notes and transcripts concerning observation of successes and failures regarding the curing of eye disease.  As soon as information regarding eye disease was organized outside of oral tradition and mythic lore, ophthalmology made a secular shift that made further progress more of a possibility.[10]  The next step of that progress is the topic of this first chapter:  the shift from a loose collection of notes and observations of cures for eye inflictions to philosophical contemplation of the eye’s function. 

            With the advent of natural philosophy, thinkers began to ponder the nature of things and their functional expression in human life.[11]  This fueled the desire to learn about the various parts of the body, especially the eye, as it sits at the threshold of sensory input and reflection.   Due to philosophical strategies governing the times, mental speculation as to organ function was considered superior to any form of actual gross dissection of bodies (human or animal).[12]  As Wade states, “observation was frequently subservient to philosophical doctrine.”[13]  This characteristic holds for all contributions of this time period.  Dissection was thought to be not only unnecessary, but sometimes even religiously taboo.[14]  Not until the Hippocratics and certainly the inception of the Alexandrian school and true anatomical study would dissection of bodies be a potent learning tool.  Although some authors hold that this time of philosophical speculation was detrimental to ophthalmology and the pursuit of eye structure and function, it actually gives the eye more depth and character, and shows how powerful the mind really is.  It is interesting that despite faulty interpretation, ancients were able to hold the eye in just as much or more esteem as we do today with the truth about the eyes at our disposal.

            Although lacking the detail of dissection-based study, pre-Hippocratic anatomy was able to construct some fairly accurate models of the eye.  Thinkers like Empedocles and Democritus would be responsible for many of the physiological theories later adopted by the Hippocratics and others.[15]  There was the recognition of a transparent cornea continuous with an opaque sclera, both lined with a layer with a perforation which formed the pupil.[16]  There was also the recognition of fluid and a canal that led from the eye to the brain.  It is important to note, however, that throughout these early attempts at speculation, primitive supernatural concepts, such as the presence of visual spirits, remained a potent force in the explanation of eye function.

          The first figure to be associated with study of the eye during pre-Alexandrian times was Alcmaeon, during the sixth century B.C.[17]  He is credited with the first speculative recognition of the optic nerves, and his postulation of eye structure is paradigmatic of the philosophical processes used by other contemporary thinkers to arrive at theories.  He first separated froneÝn from aŢst‹nesyai, or the psychic from the physiologic aspects of sensory perception.[18]  Alcmaeon placed the seat of sensation in the soul, which resided in the brain, and was therefore obliged to allow for the acquisition of sensory information to travel from the sense organs to the brain for processing.[19]  His assumption was that hollow canals must flow from each of the sense organs and empty into the brain, the eye containing a tubular connecting link.  Even the name attributed to the structure by Alcmaeon marks the claim as speculation.  Alcmaeon called this structure connecting the eye with the brain pńrow (“canal”),[20] nomenclature that would continue to be used for some time.[21]  It was either the fluid that had been noted, or more likely the visual spirit (later called pneuma) that traveled through the canal sending information to the brain.  Had Alcmaeon arrived at the notion of pńrow and accompanied it with dissection, he would have seen that the optic nerve is solid, and unable to accommodate the transmission of any semisolid substance from the orbital cavity to the brain.[22]  He would have most likely kept searching for a structure that fit his mental picture.  Regardless of its lack of truth regarding the eye’s true mechanism, Alcmaeon’s ability to correctly identify a major ocular structure via reason alone is remarkable.  He also correctly placed the final location of optic sensory processing in the brain, and posited that perhaps it is the transparency of the eye that allows for sight to occur; an idea that would later be heavily endorsed by Aristotle.[23]  Although Alcmaeon is associated with the formulation of the optic nerve via speculation, he could not ignore the phenomena of experience as clues to ocular mechanisms, commenting on flashes following a blow to the eye.  Wade notes this with text attributed to Alcmaeon: “the eye obviously has a fire within, for when one is struck [this fire] flashes out”.[24]  It is not apparent that Alcmaeon worked out the relationship between light and fluid in the eye.  The bulk of the anatomical and physiological contributions from the pre-Hippocratic era would come from Empedocles and Democritus.  These theories would expand on the importance of light and Alcmaeon’s link between the brain (pńrow) and the eye.

            Despite Alcmaeon’s[25] contributions to the nature of the eye, Empedocles (490 B.C.) is often regarded as the first thinker for whom tissues of the body gained major philosophical significance.[26]  His vast work on the eye is evidence that it held much power and deserved critical analysis.  Wade claims that the experience of light following a blow to the eye is one of the aspects of sight which initially sparked speculation about it. [27]  Empedocles’ contributions are in accordance with this claim as he strives to explain the importance of light as well as to construct a functional relationship between light and fluid.  As was the approach of many Greek thinkers over the centuries, Empedocles employed elemental philosophy, namely the relationship between fire, earth, water, and air into his ideas concerning sight.[28]  Unlike Alcmaeon and Anaxagoras, Empedocles affirmed that the object and the perception of that object are identical.[29]  Empedocles’ theory centers around two major claims: that the eye consisted of a series of pores through which internal passage was allowed; and that an internal fire was emitted from the eye.[30]  Vision then resulted from these two phenomena working in tandem.  Objects in the environment sent out effluences (nomenclature of these will be discussed later).  These effluences had both fiery (white) and watery (dark) characters.[31]  Because balanced proportions of both of these elements were located in the body, the eye must be accommodated with pores for each.  The dark effluences therefore entered the watery pores and the white effluences entered the fiery pores.[32]  The fiery pores corresponded to the internal fire of the eye, and the watery pores to the internal fluid.  Empedocles explained the appearance of light following injury by over-stimulation or aggravation of the internal fire and the fiery pores.[33]    Empedocles also attributed good and bad vision to the activity of these pores.  Good vision occurred when there was a balance of fiery to watery pores. One cause of poor vision was a clogging of the pores.  Another cause was an abundance of fiery pores, so that vision is excessively bright, or an abundance of watery pores, so that vision is dimmed.[34]  The pores were also responsible for the variety of eye colors among individuals, as degrees of internal fire differed.[35]  Seeing then occurred as a result of a double emission; effluences from objects meeting the emission of the internal fire.[36]  The obvious question that follows is how do the internal fire and fluid exist simultaneously without extinguishing the fire. Empedocles had affirmed through experience the presence of both an internal fire and fluid, so he was obligated (just as Alcmaeon with the optic nerve) to make his theory correspond.  He solved the problem through simile by equating the eye to a lantern, which also made indirect correlations to anatomical structure.  The fluid (water) in the eye enclosed the internal fire, and the water was held in place by a web-like meshwork layer lining the inside cavity of the eye (the web-like lining surrounding the inner cavity foreshadows the later nomenclature for the inner lining, Žraxnoeid®w “belonging to a spider”, “looking like a spider”).  Through this meshwork could pass the only fine particles of the fire thereby allowing for proper emission.  The web also prohibited the water from extinguishing the fire, just as light from a lantern is allowed to exit, but protected the fire from wind or water.[37]   This description presents a rather distorted picture that is difficult to mentally reconstruct.  The fire sat within the water, and the web-like membrane that sits against the water keeps it from exiting the eye, as well as keeping the water from extinguishing the internal fire.  If one imagines a membrane similar to the phospholipid bilayer of the modern cell, the description can be visualized (Fig. 2).  Although at first this claim seems grounded in philosophical reasoning alone, when Empedocles’ text from the lantern simile is quoted via Aristotle’s Sense and Sensible Objects, the cryptic nature of the idea becomes understandable:  “...So also the old venerable fire saves itself in skins, Seeking the round pupil with fine webs, which Flowing around cover the depth of the water; but Abroad strives the fire, it is spread only so far.”[38]  When listening to the text, it appears that Empedocles was observing the pupil and the iris around it.  For upon gross examination of the eye, the iris is seen to have a web-like appearance.  Speculating that the pupil accommodates the exiting fire, he seems to place the fire there.  The web lining around the fire correlates to the iris, which flows around the pupil and covers the water.  Empedocles most likely believed this external relationship was continued in the interior of the eye, the web-like membrane simply following the curve of the globe.  Although the poem does not show a perfect relationship to many interpretations of the lantern simile, it is evident that it shows dominant philosophical reasoning attempting a functional relationship with observation. 

            Although the simile of the lamp is crucial to any discussion of Empedocles and eyesight, it does not fully explain his thoughts.  Sight itself was the product of the effluences from physical objects meeting with the fire from within the eye.  This union formed what Empedocles called “light rays.”[39]  The term he used was , ŽktineŰdvlon and means “ray-image.”[40]  What happens to these light rays following union is not known.  Empedocles could not explain the nature of light, for as he saw it, it should have been identical with fire, and therefore subject to the same organizational properties as the other elements.[41]  The concepts of Empedocles’ mechanisms of the eye would later be adopted and furthered by Plato.  Empedocles’ contributions to the eye’s anatomical structure are not as significantly stressed as his physiological theories.  Diagrammatic representations that fall within the same time period are attributed to Democritus.  This is not to say that Empedocles had no concrete ideas on the subject, however, for the texts of Democritus include structures using the same nomenclature as Empedocles used in his description of the lantern such as koćrh, the word used for the pupil.  Familiarity with the  words used for certain structures shows that Empedocles was aware of accepted terminology, but tended to focus primarily on what Magnus calls “speculative anatomy.”[42]

            Democritus (c.470 B.C) is the next thinker of the time period who contributed significantly to the nature of the eye.[43]  His work shows definite knowledge of the work of Empedocles as it incorporates some of the same themes.  For Democritus, all the senses relied on touch, or some sort of physical contact, and he writes most about the application of this idea to sight.[44]  His theory is related to Empedocles’, but includes more detailed terminology, direct attention to function and structure, and eliminates double emission.[45]  Democritus thought that atoms of the soul were especially fine, smooth, round particles, and spiritual manifestations as the movement of these particles.[46]  He also believed that objects did indeed send forth emanations.  The emanations were labeled eŕdvla (“idols”), little copies of an object that carried information about the object to the eye.[47]  They are described well by Leucippus who shared Democritus’ thoughts,

            “ Now we do not actually see the objects coming nearer to us when we  perceived them, therefore, they must send to our soul ‘something’ which represents them, some image, eidola, some kind of shadow or some material...which envelops bodies, quivers on the surface, and can detach itself from them in order to bring to our soul the shape, the colors, and all the other qualities of the bodies from which they emanate”.[48] 

 

            The eŕdvla traveled through the air and made an impression on the eye.  The impression was called ¦mfasiw (“to become visible”) and was responsible for vision.[49]  The ¦mfasiw is not the same ‘light-ray’ from Empedocles’ double emanation.  The word itself in pre-Socratic texts means “modified image or representation,” and this is applicable to how Democritus explained the visual process.  The idols that stream forth from objects are modified in space before meeting the eye. ¦mfasiw is then the term for the original eŕdvla that the eye will process after undergoing modification.  All modification occurs outside of the eye.[50]  Some authors[51] hold that like Empedocles, Democritus endorsed a double emanation theory in which the eye put forth an emanation that further modified the eŕdvla.  Figure 3 attempts to diagram both sides of the argument, showing the path taken as eŕdvla are converted to ¦mfasiw and make contact with the eye.  Despite more thorough sources describing only the streaming eŕdvla and modification only as a result of traveling through space, the double emanation theory is quite interesting.  For the emanations cast out from the eye of the beholder correlate to one’s soul possibly skewing perception unique to the individual; giving a possible physiologic basis to the eye playing a role in morality.  This is certainly a debate that demands further research and investigation.  After the transformation of the image in space, the image invades the water in the eye.[52]  Whether this fluid can be named aqueous humor is another debatable issue.  In his anatomy, however, there is no distinction between an anterior and posterior chamber, so a separation of aqueous from vitreous was not possible.  In Aristotle’s de Sensu, he states that for Democritus, water is sight as well as ¦mfasiw.[53]  Hence, for proper transmission to occur, the water of the eye must capture the image.  This was considered the final task of the eye itself in the visual process.[54]  As well as adding details to physiology, Democritus  wrote about the eye’s structure.  Analysis of this anatomical approach gives more information as to his thoughts on the nature of the eye.

            Figure 4 is a diagram of the eye’s structure according to Democritus (drawn by Magnus).  This is the earliest diagrammatic representation of text the literature provides, showing that Democritus’ approach was indeed unique.  When translated, it shows better Democritus’ interpretation of extrinsic ocular features, as well as his hypotheses concerning the interior of the eye.  It is clear that Democritus describes two layers to the eye; an outer layer comprising the modern cornea and the sclera, and an inner layer with a pupil in the center.[55]  The word used for pupil, kńrh, is the same as was used in Empedocles.  Its definitions include “pupil of the eye” as well as “maiden.”  Maiden was associated with pupil because a little image of objects could be seen inside of it.  This was indeed the ¦mfasiw Democritus endorsed.  The opening into the interior is positioned anteriorly, and following directly posterior is the canal extending toward the brain.  The outer layer, which correlates to the cornea and sclera has two names depending on position.  Directly in front of the pupil it is referred to as xitĆn leptńtatow, literally, “most delicate of tunics.”  Notice the naming reflects the character of the structure, which is obviously the modern cornea; it implies the human experience with the structure, not a detached recognition.  Continuous with the xitĆn leptńtatow, on the periphery of the globe, the name changes to  xitĆn puknńtatow, literally, “most dense of tunics.”  “Thick” could be used in place of “dense” as well.  Once again, this name, pointing out the modern sclera, indicates the character of this region of the eye.  The next layer moving deeper into the eye, which includes the perforation of the pupil is called xitĆn m‹lista somfńw , literally, “most spongy of tunics”.[56]  Once again the lining is named by its apparently primary feature.  This is said to be the choroid of modern ophthalmology, and all that was really known about it was its spongy appearance.  The possibility that the retina and choroid were often confused for one another seems very likely.  As the diagram shows there is only one large internal cavity with no recognition of a lens.  The chamber is marked with the phrase Ţxmaw paxeÝa kaÜ lipar‹, literally, “thick and shiny fluid”, or “thick and oily fluid”.  This is the best description of the vitreous humor (body) of the pre-Alexandrian authors.[57]  With regards to the aqueous/vitreous debate, comparing the diagram to modern knowledge (Fig 10), there is physically no space anterior to the pupil to accommodate aqueous humor.  Its small size yielded to the vitreous body as more recognizable.  The vitreous was also the most identifiable fluid flowing from a destroyed eyeball, which was the source of any internal observations at this time.  No other writer places the vitreous in the correct location with such an accurate verbal description as Democritus.[58] 

            The next portion of the diagram is analogous to the optic nerve.  The structure is marked with two words, pńrow, retaining Alcmaeon’s nomenclature meaning “canal”, and flˇc, meaning “vein.”  The introduction of this second term shows either an alternative name for the same structure, or perhaps that the canal is accompanied by a nourishing vessel.  Based on the diagram, when Democritus’ eŕdvla traveled through the air and were subjected to modification (either by the environment alone or by the emanations of the eye as well), they passed through thexitĆn leptńtatow , entered the eye through the kńrh, and struck the Ţxmaw.  Once the image was seated in the fluid, which then made it possible to see the small image in the pupil upon looking into another’s eye (and evidence of ¦mfasiw), it could be transmitted via the fluid and accompanying visual spirits along the pńrow, for processing in the brain.  Democritus’ establishment of a more detailed physiological explanation of sight accompanied by a functional anatomy would further the power of the eye and created a stronger foundation for later thinkers to expand and elaborate on.  The gravity of Democritus’ work is eloquently verbalized by Magnus: “The example of Democritus certainly shows most clearly that Greek philosophy in the area of knowledge of nature in no way produced on idle hypotheses and clever ideas, as truly very often stated by medical authors, but had even created scientific value of inestimatable significance”.[59]  Despite predecessors of the pre-Socratics employing more empirical tools to solve ocular questions, the potency of philosophy must not be forgotten.  Indeed, as late as the 1600’s when major optical advances were being made, Kepler was quoted to say in regards to the mystery of inverted images on the retina, “I leave it to the natural philosophers to discuss the way in which this image or picture is put together by the spiritual principles of vision.”[60]  This is a blunt example of the proximity between contemporary thought and the philosophical work of the ancients. 

Knowing that such progress as Magnus describes pertains to pondering the eye definitely makes the eye unique, and worthy of an elevated appreciation.  The level of accuracy between modern ophthalmic knowledge and the diagram of a pre-Socratic philosopher with no advanced investigative tools is admirable.  It truly shows the eye’s power and ability to spark reason-based thought as well as fuel the imagination.

             

            CHAPTER II

 

A MORE EMPIRICAL APPROACH

 

 

            It is important to recall, that accompanying the various concepts and ideas put forth concerning the nature of sight, practitioners were attempting to use them to treat eye diseases.[61]  These practitioners began to feel a rather urgent need for more reliable anatomic knowledge as that which was available to them was proving insufficient.[62]  The reaction to the realization that while philosophically sound, optical theories were not doing much to advance curing techniques, was to focus more on scientifically-based methods and observation to derive information.  This trend would lead to anatomical progress, but physiological writings were still heavily influenced by previous contributors.  This once again shows the elusive and paradoxical nature of the eye as it both inspires and impedes original thought due to its significance and complexity. 

            This era of the pursuit for ophthalmic truth presents the work of many famous minds.  Hippocrates, Plato, Aristotle, Epicurus, and Euclid are just some of the thinkers that devoted much effort to unveiling the mystery of sight.  This chapter will focus on each of these thinkers’ theories, showing their incorporation of the previous work of others, as well as the establishment of their own original concepts.  Despite the growing need for empirical modes to take precedence, it was inevitable that philosophy and speculation would still be integral to physiological theories.  Similarly, empirical methods had not been completely absent until this time, their value was just beginning to gain more widespread support.  The school of Aesclepius was the first to begin the reversal of the dominance of philosophy over observation early in the fifth century B.C.[63]  Hippocrates was a member of this school, and is most heavily associated with the development of the systematic approach to the study of the body and diseases that would forever change the identity of western medicine.

             In regards to ophthalmology, Hippocrates’ (c.460-370 BC)[64] most significant contribution was to discount supernatural forces as responsible for disease.[65]  The Hippocratics focused their attention on faulty or injured bodily mechanisms as the cause of pathology instead of evil spirits.  They took extreme efforts to listen to the descriptions of eye diseases by the afflicted, carefully organizing and cataloguing case histories.[66]  These observations facilitated comparison and the recognition of trends between eye diseases that gave clues to internal structure and function.  Just as the compilations of the priests before them, the “clinical” work of the Hippocratics created a platform for further progress and marked a shift in how medical knowledge would be collected.

            Though the Hippocratic writings contain excerpts explaining how man sees, they did not in any way put forth any original theory about the physiology of sight, but rather described it based on their own observation, not on isolated thought.  Since “systematically accomplished dismemberment” (analytical dissection) was always prohibited, observation occurred via inspection of the severely wounded; a laceration or other injury having revealed the inner cavity.[67]  One Hippocratic excerpt on vision states,

“the brain or man himself sees in the following way.  A ‘vessel’[68] reaches from the coats of the brain through the bones into both eyes.  Through these two vessels the brain passes the thinnest of its slimy products[69]; in this way, this thin mass creates around itself a skin which is of similar composition as the transparent mass of the eye, namely like the part which is exposed to air[70]...These coats of the seeing part are frequently more transparent than the eye itself.  Light and everything shining will be reflected by it; we see because of this reflection.  However, what is not shining and what is not reflected will not be visible.  The other part of the surrounding coat of the eye, which is white[71] consists only of flesh”.[72] 

 

This reference describes the fluid in the eye as coming from the brain through the optic nerve and distinguishes between various coats of the eye.  The transparent areas (“seeing part”) are responsible for reflecting an image into the eye which causes vision.  Although the text does not really explain what is happening in detail, this view of the Hippocratics is an endorsement of Democritus’ physiology.[73]  The reflected image corresponds to the ¦mfasiw, the modified form of the streaming eŕdvla from the seen object.  There is the indication that sight is occurring because of the transparency of the cornea and fluid, an idea that Aristotle later promoted.  This seems to indirectly describe the refractive properties of these structures.[74]  Another important link to Democritus is that the processing of the small image which appears in the fluid (“purest moisture”[75]) is the final act of the eye itself. 

            Anatomically, Hippocrates wrote extensively about the eye and its connections to the brain.  Just as Magnus constructed the Democritean diagram based on his text, he did the same for that of Hippocrates, as Figure 5 shows.  This diagram is the anatomy of the eye that is representative of Aristotle’s writings as well, and will be referred to when Aristotle’s physiology is discussed.  Before verbally dissecting the diagram, it is apparent that there are some major differences and observational progress has certainly been made.  There are three layers to the eye (modern representations have three as well on a basic level: sclera, choroid, and retina; Fig 10), and these layers have lost the terminology xitĆn, indicating the naming process has been altered.  There are certainly more structures listed, including the addition of two vessels posteriorly, a region representing the iris, and an anterior membrane.  Hippocrates has added the term öciw to kńrh to indicate the pupil.  Some of the meanings of őcŰw include appearance, aspect, sight, and even the organs of sight themselves.  This secondary name for the pupil by the Hippocratics gives further anatomic integrity to the physiological production of an image in the fluid of the eye.  This is also the term Hippocrates uses to describe the nourishment of the pupil by the fluid in the eye.[76]  The most anterior structure indicated is marked tň mˇlan, “dark or colored [pigment]”, or “ink.”  The labeling of the diagram is very interesting here.  The diagram indicates a layer (tň diafanˇw) between the pupil and tň mˇlan, yet the most popular interpretation for tň mˇlan is the iris.[77]  The verbal description is observationally correct as the iris is certainly pigmented and resembles ink, but its lies distant from the pupil.  The natural philosophers had  accurately differentiated the pupil from the iris despite their intimacy, as changes in the pupil’s diameter (and not the iris) had been noted.[78]  The Hippocratics were aware of earlier thoughts on the iris, but there is no indication that it had a previous anatomic identity of its own. This then is the first placing of tň mˇlan and it is the most anterior structure.  Despite the presented placing of the word used for iris, this diagram, unlike that of Democritus, also includes a region correlating to the modern placing of the iris.  Interestingly, this term, stef‹nh,[79] although correctly noting the position of the iris diagrammatically as well as verbally, meaning “anything that encircles [the head] for defense or adornment”, does not indicate “iris” as tň mˇlan did.  This term refers to the corneo-scleral fold, or the black ring around the periphery of the iris.[80]  Why the placement of this fold is posterior to the iris itself, and is a more distinct area was left unresolved in the literature.[81]  The amount written by pre-Alexandrian authors with little agreement as to the name and function of the iris (it was also sometimes referred to as kńrh, the pupil and iris being named as a single unit), shows that the mysterious interaction between the iris and pupil was worthy of much attention and recognized as important in the seeing process.[82]  The speculation and observation of the iris would later influence investigators such as Galen in positing visual theory incorporating the iris.[83] 

            Next there is the layer termed tň diafanˇw or “seen through” or “transparent”.  Moving peripherally along the globe, the same layer is then called tň leukńn, meaning “bright” or when dealing with skin, simply “white”.  This layer is the same as in the depiction by Democritus.  tň diafanˇw correlates to the cornea, and is continuous with tň leukńn the sclera; these two forming the outermost layer of the eye (with the exception of the placement of tň mˇlan on the Hippocratic/Aristotlean diagram).  As noted above, the naming has changed, however, and is based more on the raw appearance of the structures, clear and white.  The term “tunic” was discarded.  The name of the middle layer of this diagram contains the same word as the corneal component of the outer layer of Democritus’ diagram.  It is slightly thinner than the outer layer and is referred to as m°nigj leptotˇra, meaning “most delicate membrane”.  Because the inner contents of the eye would not be accurately differentiated for some time, the identity of this layer is subject only to conjecture.  It corresponds somewhat to the modern site of the choroid, but other words have been implicated as meaning choroid such as Democritus’ xitĆn m‹lista somfńw.[84]  The importance of m°nigj leptotˇra simply seems to be the recognition of a middle layer between the outermost and innermost layers; especially since the inner layers were identified primarily by name alone and played no significant role in the physiology of the Hippocratics.  The next layer is the thinnest of the three and is called tň Žraxnoeid®w, meaning “appearing as a spider”, or “like a spider-web.”  Empedocles referred to a web-like structure surrounding the ocular fluid, which is certainly not only the case in the Hippocratic diagram, but also in modern knowledge of the eye.  This structure corresponds to the modern retina, being the innermost layer and indeed spider-web-like in appearance.  All that appears to have been known at this time beyond its appearance was its role in surrounding the fluid for protection,[85] and that it held important pathologic significance.[86]  The fluid in the eye, is referred to as simply tň ęgron, meaning, “moist”, or even “the fluid in the eyes.”  Hippocrates further indicates the significance of the fluid in the visual process as he claims, “it is in this moisture, that the image appears in the eyes”.[87]  As with Democritus, there is no recognition of a lens, and therefore, no distinction between aqueous and vitreous humor.  Although Democritus’ verbal description very aptly describes vitreous humor, Hippocrates’ emphasis is more on the generic moisture from the brain and its role in proper processing of the image to be seen; not on its consistency.                     

Finally, there are the three vessels that protrude from the back of the eye.  There are descriptions of the locations of these vessels and the paths that they take through the head in Hippocratic texts.[88]  The Hippocratic notion was that these were indeed hollow canals referred to as flˇc, “vein,” which accommodated the transmission of fluid from the brain.  These “optic nerves” must always allow for at least some clear passage from the brain to the eyes to properly mediate sight.  These vessels were referred to by size, but those distinctions are attributed more to Aristotle.[89]

The Hippocratics’ contributions to ophthalmology and the progression of knowledge of the eye mirrors their contribution to medicine in general.  Contrary to popular beliefs about Hippocrates and his students, they did not have all the answers, and thoughts on many structures of the body and their diseases divided physicians.  This was partly because knowledge was limited.  The Hippocratics had a strong grasp of surface anatomy, but first-hand knowledge of internal structures was dependent on wound observation.[90]  With critical structures obviously being potentially damaged, it was hard to reconstruct accurate models in this way.  Just as previous investigators did for them, however, their contributions, especially the encouragement of empirical methods, would inspire future scholars to study and elaborate on their work.

            The next thinker from this timeframe associated with the progression of thought concerning the eye was Plato (c. 427 BC).[91]  Plato’s contributions to the eye and its function are interesting as they revitalized philosophically based thought as to the nature of sight.  As Wade indicates, “...[Plato’s] theory of vision was always subservient to his philosophy of ideal forms”.[92]  Plato’s thoughts center around the mechanisms of vision and are more or less isolated from any anatomical constructs.  Similar to Empedocles, Plato held that rays emanated from the eye and were reinforced by external rays.  They then returned to the eye and produced images.[93] Other authors depict Plato’s theory as light emanating from the eye and seizing objects with its rays.[94]  There does not seems to be much support for this idea as most sources indicate the meeting of “inner light” and “outer light” as the defining feature of Plato’s theory.[95]  This idea certainly had previous origins in the theories of Empedocles and somewhat with Democritus.  Plato, however, having their work as well as the contributions of others, was able to describe his ideas in a clearer manner.  Plato assumed that a delicate, refined fire flows out from the eye and joins with the fire going out from shining bodies.  Some authors contend that from this union, or coalescence, a single body of light is transmitted to the eye.[96]  Others hold that the union yielded “rays” or “critical movements” that stream forth toward the eye.[97]  Magnus describes the process with the most detail from this point forward.  The product of the meeting of external and internal fire should pass through the eye and through to the soul.  It is in the soul, that the sensation of light is finally produced.  The whole process of sight, which can be termed, the “propagation of light” for Plato, must occur in a straight direction to best accommodate the union of the fires flowing out from the object and from the eye.[98]  Magnus also includes a pictorial representation of the process shown in Figure 6.  The description of the diagram is as follows:

“The shining object may be A, which gives out into space a cluster of divergent rays.  B may be the eye from which, as Empedocles and Plato teach, divergent rays flow out into space.  Both divergent clusters of rays meet now somewhere in the space assumed which we have marked X, X1,X2.  If both divergent clusters of rays now in the plane X, X1, X2 may have made contact with each other, contact of the rays leaving the eye with those coming from the shining object results in a shock.  This shock transmits itself now in the direction toward the eye.  Thus the rays leaving the eye in the direction of the arrow D, meet those from the object with the result that the shock produced is transmitted in the direction of the arrow G alongside the rays coming from the eye”.[99]

 

 

From this description, it is clear where Plato was influenced by Empedocles.  Plato does not seem to focus as much on the eyes themselves.  The details of their internal structure are not investigated, and they are responsible mainly for casting out the internal fire.[100]  This characteristic of Plato’s writings makes sense given that he also believed that the senses could not be totally trusted because they provided information about particulars rather than universals.[101]  It follows that he would then pay less attention to the details of their structure, and focus more on their mechanism of information collection. 

            It was mentioned earlier that the modification that Democritus said the eŕdvla were subjected to[102] hinted at possible refractive properties.  Indeed, especially with the aid of the diagram, the process that Plato describes does as well, and is very close to accurate optical properties.  If the plane containing the X’s were replaced by a convex lens, one would find the exact same pattern for the refraction of light rays through that lens.  This gives further credence to the philosophical and speculative tactics of the early thinkers in their attempt to figure out how vision occurs.[103]  It is this work that gave Plato his place in the continuum of the eye’s history.  His ability to remodel Empedoclean theory not only passed on Empedocles’ thoughts to more scholars[104], but yielded a theory that contained the perfect mix of accuracy and mystique to further inspire more thinkers to take on the challenge of advancing optical and ophthalmologic knowledge.      

            Following Plato, the area of visual studies was altered significantly.  Up to this point, most beliefs of sight centered around the emission of fire, or at least some sort of emanation from the eye mixing with environmental emanations.[105]  This view would be strongly challenged by Aristotle (c. 384 BC) who was among the first to reject the emission theory of vision.[106]  Aristotle thought that it was unreasonable to suppose that seeing occurs by something issuing from the eye.  His views would also refute other proponents of intromission theory, such as Democritus, who advocated that the impact of idols on the fluid in the eye and subsequent recognition by the soul caused vision.  Aristotle would focus more on the interactions of external (in reference to the body) light and air.[107]  According to Aristotle, the object perceived excites a motion which acts upon the eye.[108]  In On Sense and Sensible Objects and On the Soul, Aristotle describes these movements as the movements of light and air, and are carried out in the medium between the eye and the object seen, not via emanations.[109]  Despite not elaborating on the speed or propagation of the movements through space, his descriptions show a crude parallelism to the modern Theory of Undulation.[110]  Although there is little else known about the details of Aristotle’s ideas of the light, Aristotle’s thoughts on the eye itself further separate him from previous thinkers on the subject.  Aristotle’s main argument against any emission theory centered around night vision.[111]  According the to the thoughts of Empedocles and Plato, if a fire streamed forth from the opened eye to aid in the visual process, Aristotle argued, then humans should be able to see at night.  Since this was of course untrue, Aristotle said the idea was invalid.[112]  Plato contended that vision was not possible at night because light (fire) is extinguished  in darkness, just as heat and dryness are extinguished  by cold and dampness.[113]  Aristotle was not content with this explanation, as he said that neither heat nor dryness were attributes of light.[114]  Another aspect refuted by Aristotle was the reasoning that because spots appear before the smitten eye that fire must reside within.  According to Aristotle, that phenomenon occurred due the pressure of the blow mimicking the pressure of the movements of light and air during normal visual processing.[115] 

            In terms of assembling a functional anatomy, Plato is not associated much with major eye structures and their potential role in the visual process.  Aristotle, on the other hand, acquiring the scientific methods from the Hippocratics, wrote about the structures of the eye and their functions in bringing about visual sensation.[116]  It is also generally agreed that Aristotle dissected animal eyes to aid his investigation.[117]  This was a major advancement for scientific methodology, and showed the importance Aristotle placed on sound observation. Recall that Figure 5 is a representation of Aristotle’s anatomical thoughts as well Hippocrates’.  Although the diagram does depict Aristotle’s thoughts of the eye’s structure (both in location and name of structures), its various functions differ as a result of his alternative light theory (the Hippocratics having endorsed a Democritean model).  In his History of Animals, Aristotle accurately located and described the eyebrows, the eyelids, and other external features, saying, “within the eye, the moist part with which we see, called the pupil, around this the iris, and this is surrounded by the white.”[118]  Aristotle agreed with the presence of three layers to the eye, saying that these layers were intimately opposed to one another.[119]  There was also no recognition of an anterior chamber, however Aristotle did note the lens in an interesting manner.  He described the fluid of the eye as being of a uniform consistency, but exposure to air caused differentiation or modification.  Therefore, the lens was regarded as a post-mortem manifestation, a part of the fluid being over-exposed to air following death.[120]  Since the lens was considered an artifact of a dead eye, it played no role in sight and was not included in functional anatomy.  This at least brought the lens into texts and gave later authors and investigators something further to ponder.  Aristotle contributed more toward structural advancement by describing the posterior extensions from the eye: “From the eye there go three ducts to the brain: the largest and the medium-sized to the cerebellum, the least to the brain itself; and the least is the one situated nearest to the nostrils.  The two largest ones, then, run side by side and do not meet, the medium-sized ones meet...”[121] This description does not match up well with Magnus’ diagram, especially in terms of the relative sizes of the ducts that Aristotle was describing.  It is important to note, however, that the ducts are now considered to run from the eye to the brain, and not in reverse as previous scholars promoted. It is also safe to assume that Aristotle was observing the optic chiasma when he says that ducts from each eye meet.[122] 

            The Hippocratics’ posited no original theory concerning light and its relation to sight.  They were relatively content to focus on what could be observed about the eye without much speculation as to function.[123]  Their thought on function was essentially a modified Democritean perspective, as the image reflected in the fluid was the ultimate “duty” of the eye, and was responsible for sight.[124]  There are, however, transient references to the importance of the eye’s transparency (i.e. the cornea and fluid), without any attempt to figure out why.[125]  For Aristotle, these features of the eye were crucial to proper visual processing.  He would refocus the importance of the internal cavity of the eye, positing that perhaps the posterior aspects of the eye play just as an important role as the anterior.[126]  It has already been noted that Aristotle believed that objects excited a movement of light and air that made them perceptible.  Through the movement changes produced by the light, the air should enter into direct contact with the light sensitive part of the eye.  Through this contact sight may first be able to occur.[127]  For Democritus (and the Hippocratics) the light sensitive area of the eye was the fluid.  This is not so for Aristotle, as he believed fluid was necessary for transmission of sight, not sight itself.[128]  The fluid was only for the purpose of converting the movement changes of the air respective to the light sensitive apparatus of the eye, possessing mechanical function only.[129]  This was true of the pupil as well, its purpose being to accommodate the air/light movements coming into the eye.  A verbal correlation affirms fluid/pupil similarity as Aristotle calls the pupil “moist” as well.[130]   Therefore seeing does not take place in the eye because it is water, but because the fluid is transparent.  Although air is transparent as well, Aristotle, noted, water is more easily compacted and held in restraint than air, so the pupil and the eye are water.[131]  He further refuted previous scholars by denying that the image visible in the pupil was the source of vision.  He stated: “The image is visible [in the eye] because the eye is smooth [like a mirror][132]. It exists not in the eye of the observer; for this phenomenon is only a reflection.”[133]  Since the pupil and fluid had mechanical functions alone, the next question would be where does Aristotle place the light-sensitive portions of the eye?  He addresses this in another passage from On Sense and Sensible Objects, saying, “For the soul of the eye or the sense organ of the soul is not at the outermost surface of the eye, but evidently inside.”[134]  Since the fluid was not light-sensitive, but merely light-accommodating, the light-sensitive portion must lay in the back of the eye.  There does not seem to be a clear description of the contact of light with the light-sensitive area, or how sight is then processed.  It can be assumed, however, that since Aristotle traced the optic nerve(s) from the eye to the brain, that he believed further communication with the brain following contact with the innermost membrane was occurring.  Let us then trace the path that movements of light and air took from the object to the eye using Figure 5 as a reference to summarize Aristotle’s thoughts.  The excited movements of light traveled from the object through the medium between object and eye.  The light pushed air ahead of it and passed through tň diafanˇw (note transparency), and passed through the kńrh,[135] and into the internal cavity.  Once in the internal cavity, tň ęgron  was responsible for modifying the light and air so proper contact could be made with the light-sensitive portion of the eye.  Again, with no apparent textual evidence, it is only assumed that the tň Žraxnoeid®w  was the this light-sensitive area, showing primitive recognition of the retina.  From there the information “flowed” (the ducts still considered hollow) through a pńrow or flˇc to the brain for interpretation.

            When analyzing the work of Aristotle on ocular mechanisms, it is clear that he had incredible observational skills.  Despite the work of credible scholars before him, Aristotle veered from accepted principles concerning the eye and posited theories that turned out to be more accurate based on modern optics and ophthalmology.  His theory of light was a precursor to modern interpretations, and his notions of how the eye processes information was a crude version of reality.  He attributed proper function to the pupil, and at least observed the structure of the lens.  His theory of the function of the fluid was the closest to a correct understanding of the function of the moisture of the eye as a dioptric apparatus.[136]  He correctly placed the light-sensitive organs in the posterior aspect of the eye and located the optic chiasma.  Despite the apt work of Aristotle his theories would be challenged and veered from many times over the centuries, yielding a mix of progression and regression in ocular thought.  Magnus describes this well saying that if later investigators would have followed the paths which Aristotle had traveled, especially concerning refraction, many disastrous heresies involving the light-sensitivity of the eyes which paralyzed ophthalmologic dogma would not have had the ability to gain popularity.[137]  Despite later conflicts, the work of Aristotle would fuel even more thought concerning the eyes which was necessary for any advancement, no matter how slow, to occur.

            Two examples from the same time period of Aristotle’s work quickly finding contemporary competition were the contributions of Epicurus and Euclid.  Each in different ways, they put forth ideas concerning sight that once again incorporated ideas from the past.  Neither thinker seems to have focused much on anatomy, but constructed theories about how sight occurred.  Epicurus (c.341 BC) shared the principles of Democritus by advocating that the surface of things incessantly detached images of themselves that flowed into the eye.  The poet Lucretius explained many Epicurean modes of optical thought in De rerum natura, and is the source of much Epicurean information. [138]  These images would first cover the pupil, then penetrate the inner eye.  The motion of the images inside the eye then brought about the execution of other processes that caused vision to occur.[139]  Hence, Epicurus took Democritean theory another step as he was not content to end the duties of the eye with simply the capturing of the image in the fluid.  Epicurus also included perspective in his theory.  When images entered the eye, they pushed a certain amount of air in front of them proportional to their original distance away from the eye.  The farther away the object, the more air its images would push in front of them when entering the eye.  Therefore, the current of air, according to its force and size, always brings about the proper estimation of distance.[140]  It is evident, then, that Epicurus was aware of theories such as Aristotle’s that acknowledged the importance of air in the visual process.  The Epicureans also attempted to explain dreams and hallucinations.  There were essentially two organs of sight: the eyes and the skin.  The eyes processed images that were of the proper size and shape to fit into the eyes, but some images were smaller and more delicate.[141]  These flowed into the pores of the skin, and entering into the body were able to excite the spirit, producing dreams, fantasy, and hallucinations.[142]  Finally, the Epicureans did not leave clear thoughts as to the nature of light.  They assumed that it should arise from a certain arrangement of atoms in which the individual atoms should mutually repulse themselves with very special strength.[143]  Whether this was made possible from the sun, or separate atoms associated with the tiny images is not know with any certainty.

            Whereas Epicurus rejuvenated Democritean thought, Euclid (c.300 BC) would heavily incorporate the mathematical approach of Plato.[144]  Although it could be argued that Euclid should be included in a time period beyond that of this chapter, he serves as a good transition point into a time of strict empirical methodology.  Euclid’s mathematical approach gave a scientific character to theories of philosophers.  Euclid based his theory from the fact that light traveled in a straight line, and vision was restricted to the cone of rays emanating from the eye and meeting the objects within it.  After striking the object, illumination of the object occurred in the eye.[145]  Notice, that unlike Plato or Empedocles, vision occurs as a result of the perceivers’ rays, not a meeting of rays including those from the object.  The rays that streamed from the eye were subject to geometrical laws, and those same principles applied to vision as well.    Like Epicurus before him, Euclid described perspective as well.  The perceived dimensions of objects corresponded precisely to the angles they subtended at the eye.[146] These visual rays were discrete, so that there was a limit to the dimensions of objects that could be detected by them, namely a threshold for visual acuity.[147]  Objects seen by rays originating in the center of the visual cone would be seen more clearly than those from the edge.  Euclid called these direct (foveal) vision and indirect (peripheral) vision respectively.[148]  Nothing could be seen entirely at once, implying that the visual rays would scan over an object (by moving the eyes) to see all of its features.  This mechanism was limited to spatial perception and could not account for aspects such as color.  In terms of what happened once the visual rays returned to the eye, there is not much known for certain.  Some observations of texts attributed to him parallel modern interpretation, namely that Euclid did in fact assume that objects emanated light which struck the crystalline body of the eye (lens) and was conducted via the retina and optic nerve to the brain.[149]  The more common belief, however, centers around visual rays from the pupil as he describes a certain innervation that flows from the brain to the eye.[150]  The optic chiasma was further described by Euclid as accommodating single binocular vision.[151]  Regardless of the direction of information flow (though most likely from brain to eye to object and back), the brain was the seat of perception and absorbed all sensory information. 

            It is evident that progress was indeed occurring during this time period, either in the form of important anatomic discoveries, or empirical mathematical approaches to solve visual and optical problems.  The work of Epicurus and Euclid would mark the end of a potent philosophical approach to investigating the eye.  From that point forward, scholars would rely  more on observational skills and previous work on the subject to develop theories to yield both a sound understanding of the eye and more efficient methods of treating eye disease.                                  

 

           

             

             

 

 

 

 

 

 

 

CHAPTER III

FROM GREECE TO ROME AND BEYOND

 

            The final time period described here is marked by multiple changes.  These changes are both geographic, cultural, and methodological.  By mid 4th century BC, the period of glory in Greek culture was coming to an end with the conquests of Alexander the Great.[152]  As with many other areas of Greek culture, the study of the eye and medicine received significant attention in Alexandria.  Founded in 332 BC, Alexandria was the epicenter of Hellenistic scientific achievement as Greek culture gradually diffused east.[153]  Here texts of medical authors from Greece, including Hippocrates, were collected around 300 BC and composed a portion of the “Great Museum” founded by Ptolemy.  The museum consisted of four sections: letters, mathematics, astronomy, and medicine, medicine being the largest.[154]  Accompanying the organizational efforts in Alexandria to efficiently compile works on important subjects by Greece’s leading minds, was concern about medical tactics in general.  Just as there was previously a demand in Greek culture for more sufficient cures for disease, the same demand surfaced in Alexandria.  Hippocratic medicine had lost popularity as is its universal approach to disease, namely humoral theory, seemed inaccurate.[155]  The resulting idea was to shift from Hippocratic maxims and give a fresh start to the study of anatomy and physiology.  One of the most important results of this shift in mentality was the dissection of human cadavers.[156]  This also aided in the foundation of medical specialties as there was a stronger emphasis on local disease rather than generalized pathogenesis.[157]  With heightened attention having been given to the eye and medical specialties becoming more influential, this was obviously a very important time for ophthalmology.  This progress in observational tactics and the teaching of human anatomy would be led by the scholar Herophilus, whose contributions to medicine in general were the source of much advancement.[158]  The progress of Alexandria would set a new standard for scholars that would be adopted and furthered in Rome.  In keeping with past trends, however, anatomic progress would mix with the rejuvenation of old theories as the elusiveness of the eye continued to mislead yet a new generation of curious minds.  As Arrington points out, ophthalmology in Rome would follow the same pattern as other elements of culture.  It would not supercede the creative genius of Greece, but rather would produce a new realistic vitality.[159]  Roman scholars who displayed interest in the eye include Celsus, Rufus, and Galen.  The work of these men showed an apt knowledge of prior ocular thought as well as the ability to make contributions which further developed the anatomic character of the eye.  By the time of Galen, the eye had transformed from a simple two-coated sphere to a highly complex system with multiple structures and functions.  This time period is another good example of just how much was accomplished during antiquity, and how much our tactics of investigation are dependent on the work of the ancients.

            As mentioned above, Herophilus (c. 344-288 BC) was a major contributor to the scientific prowess of Alexandria.  He was the first to dissect a human cadaver in public, and paid great attention to the eye.[160] According to Aetius, he wrote a special treatise devoted to the eye which was unfortunately lost.[161]  In this treatise, however, he is said to have described the ciliary processes, uvea, and vitreous humor.[162]  He was also responsible for the term “retina” to describe the innermost layer of the eye.[163]  He used the term Žmfiblhstroeid®w, meaning “net-like, which described retinal vasculature.  The term’s Latin equivalent, rete, would eventually become retina.[164]  Herophilus’ contributions also included substantial work on the nervous system, respiration, circulation, and pulse rates.[165]  His work was efficient and employed sound scientific observation, indeed using the best tactics up to this point including group dissection and discussion.[166]  Despite, the strong tactics and methods of the Alexandrian scholars, Rome began to adopt combinations of Greek and Alexandrian investigative tools, causing clinical and research-oriented medicine to prosper.  Ophthalmology was once again at the forefront of medicine as scholars adopted the curiosity of previous authors, and an abundance of ocular pathology demanded advancement in the field.[167] 

            The Greek ideals adopted by Roman ophthalmology were modified to take on more practical and concrete applications.[168]  Once again, however, due to the versatile nature of the eye,[169] it could not fully separate itself from philosophy.  The first Roman who devoted detailed study to eye was Celsus (c.25 AD).[170]  Celsus’ book De Medicina devoted at least two chapters to the eye.[171]  This text shows a strong familiarity with and strong inspiration from Greek ocular texts, and his efforts, according to Andersen, “merit our closest scrutiny and admiration.”[172]  The book took great efforts to describe many cures for eye disease, including both medical and surgical remedies.[173]  Celsus contributed little advancement to ocular physiology, however, as previously promoted theories continued to be widely accepted.  As with previous significant contributors, Magnus diagrammatically represented the text of Celsus, which can be seen in Figure 7.  It is easily seen that the eye has changed on many levels.  The use of both Latin and Greek shows his use of previous texts. The innermost coat has moved posteriorly, the internal cavity is split in the middle, and a lens-like structure is present in the middle of the eye.  Note that there is also no individual recognition of anterior structures; the names would be included in the names of posterior structures.  This shows that Celsus believed that the seat of vision and the integral mechanisms of sight were found in the back of the eye, following the influence of Aristotle.  Regarding the layers of the eye, the word xitĆn, “tunic” is once again used, and they all include eid®w, “seeing,” as a suffix.  The outermost layer is called xitĆn keratoeid®w .  This incorporates kˇratow, “wing or flank,” which verbally describes the location of the outer membrane.   kˇratow also means “horn,” as does the Latin, corneus, an obvious precursor to “cornea.”  This layer correlates to the sclera and  joins with the cornea, which shares the same name, despite Celsus having differentiated the two structures.[174]  The next layer is called xitĆn xoroeid®w, which uses the word , xńrion “an enclosing membrane of the fetus.”  This word is a precursor to choroid, and is named for its richness in vasculature.  This naming is accurate in its location as the second coat of the eye, as well as its characteristic abundance of blood vessels.[175]  This is the first appearance of a clear reference to the choroid.  This layer extends upwards and includes the iris.[176]  The third layer retains previous nomenclature as it is called xitĆn Žraxnoeid®w, incorporating “like that of a spider.”[177]  This layer corresponded to the retina, which Celsus also called the tenuissima tunica, or “tunic held most tight.”  Celsus did not display much knowledge of the retina, and as the diagram shows he took it to be incorporated into the anterior aspect of the lens and aided in retaining the vitreous body.[178]  The pupil is not given a name on the diagram, but was known and referred to in Celsus’ texts as pupilla.[179]  It is shown as a bowed out portion which impedes on the xitĆn keratoeid®w.  For the first time, an anterior chamber is demarcated, and is referred to as locus vacuus, or “empty space.”[180]  This space extends from the pupillary perforation to the internal dividing membrane.  Celsus also acknowledged fluid in this area of the eye and called it “humor.”[181]  A major advancement due to the work of Celsus is distinct recognition of the lens, which he placed in the center of the globe, and called xrustalloeidˇw, “clear,” or “crystal.”  This word had previously held great philosophical importance and during this period was considered to be the seat of vision.[182]  Celsus verbally described it as “a drop of humor like white of an egg.”[183]  The lens made a vast leap from being considered a post-mortem manifestation to being considered the cause of sight.  The final structure named by Celsus corresponds to the appearance of the vitreous body and is called tň élaoeidˇw, or “clear or transparent.”  This is observationally sound, yet it is no longer described as moist.  Celsus described the vitreous as a curdled substance.[184]  Finally, the diagram shows no hollow entrance or exit to the optic nerve, and Celsus did not mention any hollow tubes, or continuation of the retina posteriorly.  The optic nerve most likely appeared to be a continuation of the two outer layers fused together.[185]  Magnus, however, states that previous beliefs of the optic nerve (i.e. those started by Alcmaeon) continued to be promoted in Alexandria, and remained unchanged until around the time of Galen.[186]

            The next scholar from this era to further ophthalmic knowledge was Rufus (c. 100 AD).[187]  Rufus seems to be very similar to Celsus in that his work centered mostly around the anatomy of the eye and concerned itself little with physiological mechanisms.  Magnus’ representation of Rufus’ texts is shown in Figure 8.  There are many differences between his interpretation of the eye and Celsus’, as more individual attention is paid to the anterior aspects of the eye similar to Hippocrates and Aristotles.  In general, the lens has moved closer to its more accurate anterior position, and there is more detail to the coats of the eye.  Starting at the anterior aspect, Rufus once again differentiates between cornea and sclera.  The cornea is marked as ô keratoeidŻw xitĆn, the term previously used by Celsus to denote both the cornea and sclera together.  This shows how  kˇratow (“horn”) further became associated with this area of the eye and eventually became “cornea.”[188]  This word took on local significance to this region of the eye because, like a horn, Rufus noticed that the cornea, like a horn, could be split into different layers.[189]  Similar to Celsus’ texts, the sclera is continuous with the cornea and named for its color, tň leukńn, “white.”[190]  Rufus recognized the sclera to be thicker than the cornea, and therefore deserving of a separate name.  The diagram also shows a layer anterior to the sclera called ˛ epidermŰw, “upon the skin.”  This is the first reliable account of the existence of the conjunctiva.[191]  Rufus noticed that on the outermost covering of the eyeball (sclera) lies a tunic that can become red, swollen, and separated.[192]  Hence, disease once again served to promote anatomic observation.  Although difficult to decipher from his texts, Rufus seems to end the conjunctiva at the corneo-scleral margin, not including it as a cover to the cornea.[193]  Rufus also had the best understanding of the placement of the iris.  It is continuous with the same choroid layer of Celsus ( ő xoroeid®w xitĆn), but has its own distinct location on either side of the pupil and is marked ő ragoeid®w.  This word draws a comparison between the iris and [the color of] a grape.[194]  The pupil is not named in the diagram but was of course known and probably termed pupilla as with Celsus.  The lens sits just posterior to the pupil, and is included in the anterior aspect.  The nomenclature used for the lens is the same as with Celsus (xrustalloeid¤w), but there is the addition of ęgrňn (“moist”), displaying knowledge of aqueous humor.[195]  Rufus also described a watery substance in the front of the eye between the cornea and iris, further indicating aqueous humor.[196]  The anterior chamber is shown to be encircled by the same term the Hippocratics used, ˛ stefan® (“that which encircles”).  It was used to describe the corneo-scleral margin, the black ring around the iris.[197]  Rufus posited that it continued posteriorly and aided in the division of the anterior chamber from the posterior chamber.  Rufus also called it sćndesmow tÇn xitĹnvn, “the union of tunics,” as he considered this point where all the layers of the eye came together.[198]

            The posterior chamber is proportionally more accurate than Celsus’ as the lens is found much closer to the front of the eyeball.  The innermost layer, named Žmfiblhstroeid®w, employing the terminology of Herophilus for the retina, played a role in dividing the chambers, as it merges with the posterior aspect of the lens.[199]  Rufus displayed a much more complete understanding of the retina than previous authors, and despite the diagram, wrote that it emerges from the optic nerve, spreads out, and becomes flat after going forward to touch the lens with its capsule.[200]  He also believed the retina to fully enclose the vitreous, which is marked élaoeidˇw ęgrňn.  The naming of the vitreous displays knowledge of posterior fluid as well as its transparency.  The optic nerve was not differentiated as unique from any other cranial nerve as the phrase to describe it was used numerous times in Rufus’ description of head and neck anatomy.[201]  The phrase is ˇkfusiw neurĹdhw, meaning an “outgoing cord or sinew.”  Rufus no longer held that the optic nerve was hollow, and he posited that severing it would cause cessation of vision.[202]  Any attempts at systematic ocular physiology do not seem present in Rufus’ text.  Rather speculation to individual structures is discussed, some of which are noted here.  Certainly, however, his work showed much progress and keen ability to incorporate previous work with his own observation.  With many structures more or less in there accurate locations, Rufus established a framework from which later Roman investigators would greatly benefit.

            The final investigator discussed here is Galen (c.129-201 AD).[203] As Sorsby claims, Galen’s accounts are not only important because they marked an advance, but also because no further advance would be made until the sixteenth century.[204]  Galen’s accounts are truly descriptive both in their explanations of how the eye works and how the structures of the eye are situated.  Being a physician who heavily promoted Greek medical tactics, he provided an excellent summary of what was known in Greek medicine with the addition of his own experience, which included the dissection of animal eyes.[205]  Although he contributed few new ideas, and perpetuated some faulty theories, his efficiency and organization of data would make his texts a source of investigation for centuries.[206]  Figure 9 shows Magnus’ interpretation of Galen’s text of ocular anatomy.  This is by far the most detailed diagram yet, and includes recognition of surrounding structures which have been interpreted to be extrinsic eye muscles.[207]  Galen’s naming and placement of ocular structure will be analyzed, followed by discussion of his physiologic theory.

            The cornea remains unchanged in name, retaining the term keratoeidŻw.  Galen did recognize, however, the greater curvature of the cornea, which was obviously a result of observation.[208]  He posited that it was convex so as not to make contact with the lens.[209]  Next, in the anterior chamber there is the term Čoeidˇw.  This term incorporates the word for “egg” implying Galen’s clear recognition of aqueous humor and comparison to the white of an egg.[210]  The pupil is clearly marked, using the old nomenclature, xńrh, and is accompanied by a posterior space marked pnečma, “air.”  This was significant to Galen’s physiologic principles.  Beneath pnečma lies the ŕdios toč krustalloeidočw xitĆn oĺow krommńu.  This phrase correlates the membrane to either the lens itself, or the outer portion of the lens to an onion.  This is observationally sound, as the lens, upon dissection, can be teased apart, revealing multiple onion-like layers.[211]  Before moving into the posterior cavity, the corneal margin is marked with the phrase, ‰Iriw stef‹nh.[212]  This introduces the term “iris,” however, it was used by Galen to identify the corneo-scleral junction.[213]  This was also the site where the choroid and retina terminated.[214]  The drawn iris, not given a name on the diagram, is an extension of the choroid layer.  The phrase tÇn kinoćnivn toçw őfyalmoçw muÇn Źponećrvsiw describes the innermost of the two ‘new’ external layers.  This phrase indicates rectus muscles as it implies cords (tendons) which move the eyes.  By the positioning of the phrase, Galen is most likely referring to the medial and lateral rectus muscles.  The lens retains a similar name, kruotalloeidˇw, meaning “ice-like in appearance.”  The lens would serve as the seat of vision.  Directly behind the lens is the phrase ĄpipefukĹw xitĆn Źdhlńw.  This implies a certain unknown tunic of the lens.  It does not seem to be mentioned in the literature, but could possibly play a role in Galen’s physiologic ideas of the lens.  Regarding the peripheral tunics of the eye, they are three in number, and there is no clear demarcation of the conjunctiva as was present in Rufus.  The sclera bears a name from which the modern term comes, xitĆn  

sklerńw, “hard tunic.”  The choroid layer, as mentioned, extends anteriorly into the iris, and retained its previous name,  xitĆn xoroeid®w.  Galen was the first to comment on the physiologic importance of the pigmentation of the choroid.[215]  The retina, once again called Žmfiblhstroeid®w, recognizing the net-like arrangement of blood vessels, is found as the inner membrane and surrounds tň éaloeidˇw, the same term Celsus used to describe the vitreous.  Its anterior aspects aid in holding the lens in place.  The retinal layer narrows in the posterior aspect of the eye along with the other two coats to form the optic nerve, now called the öciw nečron, “seeing cord.”  He describes the optic nerves as two processes that extend from the brain to each of the two eyes.  They are very tough and hard and expand and unfold when they reach the eyes, surrounding the vitreous humor on all sides like a garment, finally attaching themselves to the crystalline body.[216]  Although Galen recognized this structure as solid, staying grounded in the theories of his Greek predecessors, his physiology would include a hollow canal similar to Alcmaeon’s.[217]

Physiologically, Galen had two theories to choose from, namely either intromission (promoted by Aristotle) or extramission (or emanation, promoted by Plato and others).  Galen chose the extramission theory as it corresponded well with his image of sight as a function of the optical pneuma, seen earlier, which flowed from the brain to the eyes.[218]  This pneuma was a visual spirit that filled the space in front of the iris, dilates the pupil, and surrounds the lens.[219]  The posterior chamber served to aid diffusion of the pneuma onto the lens.[220]  He said that the iris is pierced in order to let out the light which comes from the brain.[221]   Shastid includes an excerpt from Galen’s text which clearly depicts his physiological theory:

“Rays, called visual rays, proceed from the brain, down to the optic nerve to the retina, from the retina, to the crystalline body, and then from the crystalline body out through the pupil, through the aqueous humor, the pneuma, then through the cornea and so on, in exactly straight lines to the object looked at.  The visual rays then return by precisely the same path which they took in the outward direction, and re-entering through the cornea, pneuma and aqueous, then reach the crystalline body, or the essential visual organ.  Here vision is, in some mysterious manner, manufactured, or elaborated, and then transmitted, by means of the retina and nerve to the brain.”[222]

 

The use of “visual rays” shows clear familiarity with the work of Empedocles and Plato.  His own contribution is the addition of the pneuma, however, visual spirits had always been considered part of the process (although details were not included).[223]  The process begins and ends in the brain, another concept put forth by previous scholars.  Gorin states that when the rays reached the optic chiasma, Galen considered it to be like a cyclopean eye that distributed visual spirit evenly to the two eyes, and aided in binocular vision.[224]  Some other important functional features include Galen’s attribution of the lens as the seat of vision.  He arrived at this notion by noticing that hypochymata [cataracts] formed between the crystalline body and the cornea took away sight.[225]  The retina was important as it nourished the vitreous, and perceived alterations which occurred in the lens, transmitting that information to the brain.[226]  Hence despite faulty interpretation of the lens, Galen correctly confirmed the retina’s role as an interpreter and communicator of optical information.  The choroid was important in the process as its rich supply of blood vessels nourished the retina, and its pigmentation prevented the dispersion of light so that the rays could be emitted in a uniform manner.[227]  Once again, although the direction of the light is reversed in reality, these two functions are indeed functions of the choroid layer.  Galen had constructed an eye that was admirable in its anatomic detail and correlation to function.  It must be considered, that no matter how incorrect Galen was, his theory was the result of sound research, observation, and reason.[228]  His thoroughness and attention to detail made him one of the most famous medical authors in history.  His work on the eye would later be taken up by many scholars around the world, which would lead to further progress and input from experts in a variety of fields, including anatomy, physiology, mathematics, and philosophy.  Galen marked the end of ophthalmology under Greaco-Roman control, as it would soon become the forte of Arab scholars in the Middle-East.[229]  His work was a great tribute to previous ocular investigation, as he shared the same curiosity of the nature of the eye as the first Greek investigators whom he admired so much.

 

 

 

 

 

 

 

 

 

 

 

 

 

CONCLUSION

 

In reflecting on what has been analyzed, it is important to remember that the diagrams used contain some unintentional bias.  It would have been impossible for Magnus to reconstruct verbal descriptions of the eye without incorporating at least some of his own knowledge as to the structure of the eye.[230]  They are still, however, incredibly useful for analysis of the progression of ancient ocular thought.  The ancients had an incredible respect for the eyes, which have been referred to by authors such as Empedocles as “the perfect harbors of Cypris,” showing strong philosophical importance.[231]  This philosophical importance along with admiration for their functional mystique, caused them to be so heavily studied.  The Greeks and the Romans were remarkably keen observers and attached an importance sometimes even to minute variations in the eye that quite escape the attention or even knowledge of the average person today.[232]  This is indeed the point of this thesis.  Our culture today puts an incredible amount of importance on sight.  When something such as the eyes is so highly regarded, I think it makes sense to figure out why.  Off course, it can be said that the eyes are revered for their practical purposes of facilitating life; a purpose that is as old as mankind.  Hopefully, however, this thesis has shown that there is more to the eyes than simply practicality.  The nature of the eyes elicited theories which attributed to them activities that in reality were not present.  We have seen fire emanate from the eyes, visual spirits flow through the head, ocular pores which serve as filters, and comparisons made between the eye and a fetus.  These extraordinary theories have been passed down from generation to generation and have continued to fuel investigation into solving ocular questions.  When one stops and realizes that our eyes are structurally the same as those that sparked such interesting theories among the ancients, a deeper appreciation of our own eyesight occurs. 

Finally, after studying the progression of the study of the eye in antiquity, I have noticed a pattern which is continued today.  The nature of the eye caused the ancients to formulate and speculate spectacular ideas as to how it worked.  Eventually, these theories were perfected and “tamed down” into a rational, indeed accurate, depiction of ocular structure and function.  Today, however, continuation of the same methodologies such as dissection, observation to detail, and speculation, has led the pattern to reverse.  Recent research shows that perhaps the eye is indeed doing more than modern science has been giving it credit for.[233]  This research indicates the eye is monitoring light even if it is blind.  This monitoring then serves to activate hormones which establish healthy circadian rhythms.  Continued and fruitful research in this might well confirm the notion that the eye is capable of complex communication with the environment beyond one-dimensional processing light; an idea that the ancients posited centuries ago.[234]  This is one more reason to analyze ocular theory of antiquity, as perhaps some of their theory is more applicable then we think.[235]  Analysis of ancient theories of eyesight enhance the understanding of and appreciation for the most unique organs of the body.    

      

           

           

                     

           

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WITH SPECIAL THANKS TO XAVIER UNIVERSITY FOR OFFERING THE HAB PROGRAM AS WELL AS:

 

FR. JOHN LaROCCA, PROGRAM DIRECTOR

FR. FRED BENDA

DR. LISA CLOSE-JACOB

DR. EDMUND CUEVA

DR. ARTHUR DEWEY

DR. SHANNON BYRNE

 

 

 

 



[1] Hugo Magnus, Ophthalmology of the Ancients (Belgium: Wayenborgh, 1998), 32.

[2]  S. Ry. Anderson, MD  The Eye and its diseases in antiquity A compilation based on finds from

                ancient times. (Copenhagen: Rhodos Publishers, 1994), 9.

 

[3] George E. Arrington, Jr. MD. History of Ophthalmology (New York: MD Publications, Inc, 1959), 11

[4] Andersen, 33.

[5] Andersen, 21-33

[6] Jim Dryden..  More Than Meets the Eye, Washington University St. Louis Website (accessed 12/03)

[7] Solmsen, Friedrich.  “Tissues and the Soul:  Philosophical Contributions to Physiology,” The

                Philosophical Review 59 (1950) [e-journal]<http:www.jstor.org (accessed 25 Nov 2002) 435.

 

[8] Magnus, 34.

[9] Magnus, 33-34.

[10] Magnus, 37.

[11] Magnus, 40.

[12] Magnus, 40.

[13] Nicholas J. Wade, “Light and sight since antiquity,” Perception 27 (1998): 637.

[14] Roy Porter. The Greatest Benefit to Mankind.  London: W.W. Norton & Company, 1997. 56.

[15] Magnus, 68.

[16] History of Ophthalmology. “Anatomy”  A Historical Tour of Ophthalmology. Home page online.

    . 1.

 

[17] Magnus, 41.

[18] Magnus, 54.

[19] Magnus, 41.

[20] All translations from Liddell and Scott Greek-English Lexicon, Traupman’s Latin & English Dictonary, 

    the source within which the word was used, or my own translation.

[21]History of Ophthalmology “Anatomy” 1.

[22] Magnus, 41.

[23] Magnus, 64.

[24] Wade, 639.

[25] As well as other thinkers such as Anaxagoras (discussed in Magnus).

[26] Solmsen, 436.

[27] Wade, 638.

[28] Wade, 638.

[29] Magnus, 65.

[30] Wade, 639.

[31] O’Brien, D. “The Effect of a Simile: Empedocles’ Theories of Seeing and Breathing,”

                The Journal of Hellenistic Studies 90 (1970) [e-journal]<http://www.jstor.org

                (accessed 27 Jan 2004) 140.

 

[32] O’Brien, 140.

[33] Magnus, 65.

[34] O’Brien, 140.

[35] Magnus, 49.

[36] Magnus, 65.

[37] Magnus, 65.

[38] Magnus, 66.

[39] Magnus, 66.

[40] Robert B. English. “Democritus’ Theory of Sense Perception,” Transactions and Proceedings of

            the American Philological Association 46 (1915) [e-journal]<http://links.jstor.org.  218.

 

[41] Magnus, 66.

[42] Magnus, 32.

[43] Magnus, 66.

[44] English, 217.

               

 

[45] The literature shows conflicts on this issue.  Some authors hold that Democritus included double emission in his theory, while others deny it.

[46] Magnus, 67.

[47] English, 217.

[48] Wade, 639 (other qualities including position and three dimensionality).

[49] English, 218.

[50] English, 219.

[51] Including Robert English.

[52]Magnus, 67.

[53] English, 217.

[54] Magnus, 67.

[55] George Gorin, MD. History of Ophthalmology (Wilmington: Publish or Perish, Inc, 1982), 12.

[56] Magnus, 49.

[57] Magnus, 55.

[58] Magnus, 55.

[59] Magnus, 67 eg: even today the numerous layers of the eye are referred to as “tunics”.

[60] Wade, 638.

[61] Which were highly common; both mechanical defects in the visual process, as well as external infections which

   were called ophthalmias.  These diseases became a standard example for the fragility of the human condition

   and the pains of old age. Andersen, 72. Plantzos, 101.

[62] Magnus, 41.

[63] Wade, 646.

[64] Wade, 646.

[65] Arnold Sorsby, MD.  A Short History of Ophthalmology.  London: Staples Press, 1933.  12.

[66] Arrington, 24.

[67] Magnus, 41.

[68] the optic nerve.

[69] ocular fluid (vitreous meets “slimy” description).

[70] the cornea.

[71] either the sclera or tendon tissue (correlations by Hirschberg).

[72] Julius Hircschberg.  The History of Ophthalmology in Antiquity.  Bonn: Wayenborgh, 1982. 71.

[73]Magnus, 68.

[74] The debated modification that the viewer is responsible for to the object could be correlated to refraction as well.

[75] Hippocrates, Places in Man, ęgrÇ tÇ kayarvt‹tv  VIII, 279.

[76] Hippocrates, VIII, 278.

[77]Walton Brooks MacDaniel.  “The Pupula Duplex and Other Tokens of an “Evil Eye” in the Light         

                of Ophthalmology,” Classical Philology 13 (1918) [e-journal]<http://jstor.org (accessed

                21 Jan 2004). 337.

 

[78] Magnus, 49.

[79] W.K.C. Guthrie.  Anaximenes and TO KRUSTALLOEIDES,” The Classical Quarterly, New

                Series 6 (1956) [e-journal]<http://www.jstor.org (accessed 21 Jan 2004).  41.

 

[80] Magnus, 48.

[81] This could be attributed to the interpretation of Magnus in reconstructing the text.

[82] Magnus, 49.

[83] McDaniel, 340.

[84] Magnus, 51.

[85] Hippocrates, 288.

[86] Magnus, 50.

[87] Hippocrates, VIII, 280.

[88] Hippocrates, VIII, 291-306.

[89] Magnus, 55.

[90] Porter, 56.

[91] Magnus, 70.

[92] Wade, 640.

[93] Arrington, 28.

[94] History of Ophthalmology. “Introduction”  A Historical Tour of Ophthalmology. Home page

                online.  Available from

                .

 

[95] Gorin, 14.

[96] Dimitris Plantzos. “Crystals and Lenses in the Graeco-Roman World,”  American Journal of

                Archeology 101 (1997) [e-journal]<http://links.jstor.org (accessed 9 Jul 2003) 459.

 

[97] Magnus describes it in this way, perhaps because these “fires” are not detectable by the human eye and so they

     should not be termed “light”. 70.

[98] Magnus, 70.

[99] Magnus, 71.

[100] Magnus 70-72.

[101] Wade, 640.

[102] Again, either during  travel to the eye alone, or modification by the eye itself, depending on the author.

[103] Magnus, 72.

[104] O’Brien, 140.

[105] O’Brien, 144.

[106] The History of the Eye.  A History of the Eye. Home page online.  Available from

                http://www.standford.edu/class/history13/earlysciencelab/body/eyepages/eye.html. 1.

[107] Arrington, 28.

[108] Arrington, 28.

[109] Magnus, 72-73.

[110] Magnus, 72.

[111] Wade, 640.

[112] O’Brien, 141.

[113] Wade, 640.

[114] Wade, 640.

[115] O’Brien, 161-162.

[116] Thomas Hall Shastid, MD.  An Outline History of Ophthalmology.  Southbridge: American

                Optical Company, 1927. 569.

 

[117] Sorsby, 19.

[118] Arrington, 28.

[119] History of Ophthalmology, “Anatomy” 1.

[120] History of Ophthalmology, “Anatomy” 1.

[121] Wade, 646-647

[122] History of Ophthalmology, “Anatomy” 1.

[123] Magnus, 67.

[124] Magnus, 67-68.

[125] See page 20.

[126] The anterior having been the sight of transmission and reception of light.

[127] Magnus, 73.

[128] Gorin, 12.

[129] Magnus, 73.  This is reminiscent of Democritus’ modification of the  eŕdvla.

[130] p. 28-29, footnote 59.

[131] English, 218.

[132] i.e. like water

[133] Wade, 640.

[134] Magnus, 73.

[135] Note that őcßw would not be Aristotle’s preferred term for the pupil as sight was not occurring in it as for the

    Hippocratics.  This is affirmed as kńrh is the term for pupil in various excerpts from On Sense and Sensible

    Objects in Magnus, 74.

[136] Dioptric: Refractive; assisting in vision by refracting  and focusing light.  Magnus, 74.

[137] Magnus, 74.

[138] Magnus, 68.

[139] Magnus, 69.

[140] Magnus, 69.

[141] Magnus, 69.  Empedoclean interpretation of the senses.

[142] Mangus, 69.

[143] Magnus, 69.

[144] Wade, 641.

[145] Wade, 641.

[146] Wade, 641.

[147] Wade, 641.

[148] Wade, 641.

[149] Hirschberg, 157.

[150] Hirschberg, 157.

[151] Hirschberg, 157.

[152] Gorin, 13.

[153] Lindberg, David C. “Medieval Islamic Achievement in Optics,”  Optics and Photonics News

                (2003) [journal on-line]available from http://www.osa-opn.org (accessed 21 Jan 2004)

[154] Gorin, 13.

[155] Arrington, 31.

[156] Arrington, 31.

[157] Arrington, 31.

[158] Arrington, 32.

[159] Arrington, 33.

[160] Sorsby, 20.

[161] Sorsby, 20.

[162] Arrington, 32. ciliary processes: muscles which contract to change shape of lens. uvea: pigmented epithelium on

    posterior surface of the iris (gray’ anatomy, p.831).

[163] Magnus, 140.

[164] Magnus, 140.

[165] Arrington, 32.

[166] Gorin, 13.

[167] including local inflammations, lippitudo; cataractous lenses (termed glaćkvma), and suffusio (ępńxuma).   Magnus devotes much attention to ocular pathology, however there seems to be little agreement among sources concerning the meaning of the diseases. Magnus, 180.

[168] Arrington, 33.

[169] i.e. sitting at so many thresholds including physical, spiritual, and psychological (see introduction p.3).

[170] Wade, 647.

[171] Shastid, 570.

[172] Andersen, 73 & 76.  Some modern authors are not as complimentary, however, as Hirschberg states about Celsus,

    “he did not understand the subject.” Sorsby, 20.

[173] Arrington, 37-40.  Many topical treatments (collyria)* are mentioned as well as cataract couching and excision

    of pterygia (a wing-like ingrowth of connective tissue in the cornea)*      *Andersen, 112 & 114.

[174] Magnus, 136.

[175] Indeed tiny blood vessels supply the choroid which nourish the eye. Tortora and Grabowski, 464.

[176] Magnus, 136.

[177] See Chapter II, Fig. 5.

[178] Magnus, 140.

[179] Magnus, 141.

[180] source of suffusio, Arrington, 39.

[181] Magnus 143.

[182] Guthrie, 41.  Also the source of faulty vision, Wade, 648.

[183] Magnus, 144.

[184] Magnus, 144.

[185] Sorsby, 20. Which is actually closer to reality.

[186] Magnus, 146. This is obviously one of the myriad points about which authors disagree.

[187] Wade, 648.

[188] See above, p. 39.

[189] It is alluded to in his texts that pre-Alexandrian scholars may also have had this knowledge. Magnus, 137.

[190] Wade, 647.

[191] The conjunctiva does in fact sit anterior to the sclera beneath an epithelial layer. Grays Anatomy, p.831.

[192] Magnus, 135.

[193] Magmus, 136.  The conjunctiva does cover the cornea and the sclera. Gray’s Anatomy, 825 & 826.

[194] Magnus, 137.

[195] Magnus, 144.

[196] Sorsby, 22.

[197] The diagram includes ĺriw on the iris, but Magnus asserts that although Rufus used this term,  ő ragoeid®w

   was more commonly used.   ĺriw was not used chiefly for the iris (and not the corneo-scleral margin) until

     later ophthalmology.

[198] Magnus, 139.

[199] Magnus, 140.

[200] Magnus, 140.

[201] Magnus, 147.

[202] Magnus, 146.

[203] Gorin, 14.

[204] Sorsby, 22.

[205] He was hated by Roman physicians due to his enormous practice, and was called “Graeculus,” “little Greek.” 

    Gorin, 15 & Sorsby, 24.

[206] Gorin, 15.

[207] Sorsby, 24.

[208] Sorsby, 24.

[209] Arrington, 45.

[210] Arrington, 45.

[211] Gray’s Anatomy, 840.

[212] the middle word of this phrase seems to be cut off in the diagrams.

[213]ĺriw”: messenger God (possible link to Galen’s physiology); or any ring-like substance like around the pupil.

     

[214] Sorsby, 22.

[215] Arrington, 45.

[216] Shastid, 572.

[217] Sorsby, 24.

[218] A History of the Eye, 1.

[219] History of Ophthalmology. “Physiology”  A Historical Tour of Ophthalmology. Home page

online.. 1.

[220] Sorsby, 24.

[221] McDaniel, 340. Hence, correlation to the messenger God.

[222] Shastid, 573.

[223] Dickie, 27.

[224] Gorin, 15.

[225] Shastid, 572.

[226] Shastid, 572.

[227] Shastid, 572 & Arrington, 45.

[228] This is the case of the other thinkers presented here as well.

[229] Sorsby, 24 & Lindbergh, 33.

[230] Wade, 646. Magnus working in 1901.  These diagrams would not be recognizable by their original authors.

[231] Solmsen, 439.

[232] McDaniel, 345.

[233] Dryden, 1.

[234] Especially in their accounts of the Evil Eye, e.g. McDaniel, 335-346.

[235] See also Jim Dryden, “Researchers identify key risk factor for cataracts”, Washington University

    St Louis Online, for discussion for air’s destructive characteristics on vision (see air and vitreous p.29 of

    this work).