Artificially-induced High Myopia and the Mechanism of Accomodation -------------------------------------------------------------------- _N-ted theory of accommodation is wrong? The following is an account of an experiment which produced a very surprising and unexpected result which calls into question current theory. The standard explanation of myopia is that in the myopic eye, the light rays passing through the crystalline lens come to a focus in front of the retina, and that this is usually caused by the eyeball being too long. (2, 3) The result is blurred vision for objects at a distance. I decided to test this theory by compres-sing the eyeball, with the idea that this would lengthen it longitudinally (by compressing it approximately in the middle). In other words, the object of the experiment was to deliberately produce myopia. My method for compressing the eyeball is explained in Appendix A. Since I could hardly ask someone to be the subject of an experiment designed to worsen his vision, the subject of the experiment necessarily had to be myself. I reasoned that if I did succeed in lengthening the eyeball, then my vision for distance would become blurred, i.e. I would become myopic. However, because I was already myopic (O.D. -7.75-1.25; O.S. -5.50 -1.50), the object of the experiment would be to increase the degree of myopia. I began to wear the device, strapped to my head, for three to four hours per day (used for distance vision only) and periodically checked my visual acuity for any sign of increased blur. After several weeks of this regimen I noted the first definite sign of change--but precisely the OPPOSITE of what I had predicted: _my visual acuity for distance had definitely increased_. In fact, with continual wearing of the device I eventually reached the point that my visual acuity (which for many years had been myopic, with uncorrected acuity at around 20/600) was in the range of 20/30 - 20/40. To a lifelong myope this seemed almost the equivalent of perfectly clear vision. At the time I was 35 years old and had been wearing corrective lenses, of gradually increased power, since the age of six. It seemed obvious that this remarkable change in acuity had been caused by something to do with the experiment, but by what means? Another puzzling factor was that even with my near-sharp acuity, blur was still present. The subjective experience of this effect was as if two photographic trans- parencies, one blurred and one sharp, were superimposed one on the other. It should be made clear that this was monocular, and approximately to the same degree in each eye. The crucial question was, how had squeezing the eye produced dual vision? There are a few reports in the literature on double focal points resulting from cataracts, but this case was clearly different. I hypothesized that the creation of dual vision was the result of contraction of the superior oblique muscles, which had exerted pressure on the globe, which was transmitted through the sclera to the vitreous, forcing the vitreous against the back of the lens and flattening its periphery. Rays passing through this outer region of the lens came to a focus at a point very close to the retina, which produced the secondary image (clear vision), while the rays passing through the axial (central) region of the lens came to a focus in front of the retina, which produced the primary image, which was severely blurred. Because I was so close to emmetropia (I thought), I decided to increase the degree of rotation of the images to the maximum possible while still maintaining a fused image, and to increase the wearing time of the device. The results were disappointing. First, although without correction I could still read the 20/30 line of the Snellen chart (and sometimes even the 20/25 line), I noticed that my acuity WITH corrective lenses had deteriorated markedly. For no valid reason other than curiousity, I decided to test my acuity with plus lenses and got another surprise. With +3.00 lenses I could STILL read the 20/30 line. In other words, I had now become, simultaneously, a high myope and a high hyperope: vision with the primary image, from rays passing through the axial region, had further shortened which increased my myopia even further, while rays passing through the peripheral region of the lens had shifted to a point behind the retina. I eventually reached the point that with +14.00 lenses I still maintained nearly emmetropic acuity, within a field of severe blur. Apparently, the prolonged severe pressure of the vitreous on the lens had produced such extreme flattening that the peripheral-ray focal point had been pushed to a position several millimeters behind the eyeball. Also by this time, my visual acuity with my original corrective lenses had suffered marked deterioration. My original lenses had become totally inadequate, and I required a new prescription: O.D. -11.75 -2.25; O.S. -9.00 -2.00. In other words, in less than two months I had increased my myopia by some 5 diopters. At this point, I decided to stop. The Persistence of Accommodation and the Etiology of Myopia The creation of a dual mode of vision was quite remarkable, but another intriguing (and troubling) finding was that the dual vision persisted even after the experiment was stopped. I reasoned that the lens had become permanently distorted as a result of vitreous pressure. (This, of course, quickly dampened my initial enthusiasm that I had discovered a cure for myopia). The most significant point, however, is that these changes in acuity must have come principally not from elongation of the globe, but rather from changes in the shape of the crystalline lens. I eventually concluded that what I had was a case of spherical aberration carried to an extreme degree. (See Spherical Aberration, Appendix B). I reasoned that if it were true that the cause of my dual vision was spherical aberration resulting from deformation of the lens, then the lens had become accommodated, since accommodation is always accompanied by spherical aberration, and vice versa. Therefore, the persistence of dual vision indicated that the accom-modation also persisted. I had increased my myopia remarkably, but as a side effect had created a second mode of vision close to emmetropic. Implications I concluded that the bizarre results of this experiment had major implications for the conventional wisdom about eye mechanisms in several areas, and I propose the following: 1. Accommodation is actuated by contraction of the ciliary muscle, true, but probably not by relaxation of the zonule so much as by the cilliary muscle pulling the vitreous against the posterior surface of the lens (this is not a new idea). 2. The principal cause of myopia resides in the lens, and to a lesser degree in axial length. 3. The argument that myopic lenses are not accommodated because they tend to be thin is wrong. This could be explained by long-term compression, which produces a permanently accommodated lens in which only the periphery is flattened. 4. The _action of the extraocular muscles can cause the lens to accommodate_. Obviously, these statements directly contradict much of the conventional knowledge about eye mechanisms, for which there is a mountain of evidence. Below I will attempt to answer. The Zonule Relaxation Theory of Accommodation If the dual vision observed was caused by vitreous pressure, then the Helmholtz-Fincham theory of accommodation can not be correct. Briefly, the Helmholtz-Fincham theory states that the lens accommodates by means of relaxation of the zonular fibers. "Accommodation results from decreased tension: the driving force--the motor--is the lens capsule. The decreased tension theory is attributed to Helmholtz. Considering the evidence, there is little reason to still call it a theory. Its only serious rival, proposed by Tscherning at the turn of the century, just survives by textbook repetition." (5, p. 87) The hypothesis of vitreous pressure comes up against three exceptionally strong arguments. The conventional view is that: 1) The vitreous is unimportant in accommodation. This is proven by experiments in which accommodation occurs even without the presence of the vitreous in cases of vitrectomized eyes. 2) When the lens is freed from zonular tension, it assumes a more spherical shape, i.e. increases its power. 3) The zonular fibers relax during accommodation. When accommodation is observed in an eye in which the iris is absent, thereby exposing the zonules to view, they are clearly seen to relax their tension. My answers to these objections are as follows: 1) That the vitreous is not required for the eye to accommodate: Almost all eye researchers support this view. For example, Fisher states that "The vitreous plays a negligible role during accommodation in modifying the position or shape of the lens." (6) Burian and Allen state that "...our observations on the periphery of the vitreous surface strongly suggest that the vitreous body, far from pressing on the periphery of the lens, was actually under reduced tension during accommodation." (8) However, a few researchers contradict this view. Araki reported that in experiments on pig, dog and cat eyes, "...it is suggested that tension of the ciliary muscle/zonules stretching from the posterior surface of the lens was increased by forward movement of the ciliary body and consequently it resulted in pressure to the posterior _peripheral_ (my emphasis) part of the lens...the increase in pressure of the vitreous body due to contraction of the accom- modative muscle is considered to be the most important factor for the transformation of the lens." (10) Suzuki performed an experiment in which he injected radiopaque material into the vitreous of a cat's eye, which during accommodation moved in a direction indicating that the vitreous was forced against the back of the lens and also somewhat toward the posterior pole of the lens." (11) An experiment by Koke produced a similar result. He injected cat eyes with radiopaque material and took X-rays during miosis and mydriasis, which showed that during accommodation the vitreous moved toward the lens and inward toward the optic axis. (12) The experiment that is most closely related to mine, because it involved external pressure on the globe, is that of von Pflugk. He cut windows in the equatorial region of bovine eyes and injected a drop of dye into the anterior vitreous, midway between the ciliary body and the posterior pole of the lens. Pressing against the ciliary body from the outside in a radial direction made the dye move toward the lens capsule. (13) 2. The second objection to the vitreous/lens hypothesis is undoubtedly the strongest of all: the demonstration that when freed from the tension of the zonule, the lens assumes a more spherical form. It is probable that the experiments of Fincham, more than any other factor, tilted opinion away from Tscherning's theory and towards that of von Helmholtz. In what is undoubtedly the demonstration that clinched the case for zonular relaxation once and for all, he showed conclusively that without the tension of the zonule, the lens becomes more spherical. An eye was made to accommodate for distance viewing by the instillation of atropine and then removed from the orbit and pointed upward after dissection of the cornea and iris. The profile of the lens can then be photographed, and in this condition it demonstrates the characteristic shape of the lens when the eye is looking at a distance. However, when the fibers of the zonule are severed all around by the sharp edge of a knife, the curvature of the anterior surface increases markedly and "assumes the shape that it has under maximum accommodation," i.e. the lens becomes thicker, as is clearly seen in the photographs taken by Fincham. This appears to be an unassailable argument. To recapitulate: when the zonules that hold the lens in place are cut, the lens immediately becomes more spherical, which obviously increases its power. To counter this argument requires rejection, not of Fincham's observation (the photographic evidence is too strong for that) but of his interpretation. When the zonules were cut and the lens became more spherical, he ASSUMED that the consequent change in the shape of the lens was the same as that which occurs in accommodation. Could this be a non sequitur? I believe that it is at least possible. It is not inconceivable that the shape he observed was not the shape that occurs in accommodation, but merely looked like it. It is possible that the lens could assume a more spherical shape under _two_ different conditions: 1) When released from the tension of the zonule and 2) When molded by vitreous pressure, with only the latter being true accommodation. 3. The third objection is based on the well-documented evidence that when the lens accommodates, the zonular fibers relax their tension. The vitreous/lens hypothesis, however, requires that there be some means to counteract the vitreous pressure. If the lens is pushed forward by the vitreous, what could hold the lens in its place? Obviously, the zonular fibers could not fulfill this function if they are relaxed. Although most of the standard textbooks on ophthalmology state simply that in accommodation the zonular fibers relax their tension, this is not the whole story. Several investigators have shown that there are two sets of fibers, and that while the anterior fibers relax in accommodation, the posterior fibers either remain tensed or increase their tension. Evidence for the existence of two sets of zonular fibers has been reported by several investigators. According to Suzuki, "During accommodation the posterior valley became swollen toward the inner direction of the eyeball. This could account for the relaxation of the zonules attached to the anterior surface of the ciliary muscle. "During more advanced accommodation, the anterior valley sank toward the outer direction of the eyeball. This could account for the _contraction_ of the zonules attached to the posterior surface of the lens (italics added). (11) An experiment by Araki showed that "electric recordings of the changes in tension of the ciliary zonules suggested relaxation of the zonules which was (sic) stretched to the anterior surface of the lens and on the contrary, increased tension of that stretching to the posterior surface (cat and dog eyes). (10) The Iris Although it may be that there are two sets of zonular fibers that contract in different ways, and it is possible that tension of the posterior zonular fibers might be sufficient to withstand the pressure of the vitreous against the lens, this seems unconvincing. What other mechanism could hold the lens in place? An obvious candidate would be the iris, if it weren't for the fact that more than a hundred years ago von Graefe showed that the lens can accommodate perfectly well even when the iris is not present. Apparently, von Graefe's demonstration was all that was needed to disprove the iris hypothesis, yet it would seem unwise to base such an important conclusion on a single case. Furthermore, just as in Fincham|s experiment, when the lens is released from traction, the more spherical form that it assumes may not be true accommodation. If this is correct, and if the full amplitude of accom-modation seen by von Graefe was not true accommodation, then his conclusion that the iris is not required for accommodation may be wrong. It is highly improbable that with the vast amount of research done on the iris, such an important function as counterpressure on the lens could remain undetected. Yet a number of reports do suggest an iris/lens connection. And it is interesting that the researchers themselves seem to be surprised by their findings. Lowe reported that "During examination of a large series of eyes that had pupils dilated after peripheral iridectomy...I was struck by the marked curvature of the anterior lens surface within the enlarged pupil. The lens frequently appeared as though it were herniating through the enlarged pupil, with the pupillary margin of the iris seeming to grip the lens." (15) Jampel and Mindel, in a report on stimulation of the oculomotor nucleus in monkeys, observed changes "... characterized by a conspicuous forward bulging of the pupillary or central portion of the iris which produced a marked convexity of the iris diaphragm and a marked increase in the depth of the anterior chamber...On observation of the eye from the side during iris-bulge, the central portion of the lens appeared to become conoidal and to move forward into the anterior chamber." (17) Burian and Allen reported that "The most remarkable change was seen in the middle one-third of the body of the iris. This part of the iris bowed backward during active accommodation, forming a deep hollow, and returned to its normal position when the eye was relaxed." And Suzuki states that "Concerning the iris, its silhouette was a slightly curved line, being convex anteriorly in the form of a physiological 'iris bombe'. On stimulation, the iris showed a peculiar change. That is, besides the change of the contraction of he pupil, the iris was bent reversely to the posterior chamber, so that the central half of the iris was held in contact with the anterior surface of the lens and the iris-lens apposition became tighter over a much larger area." In the rhesus monkey there is a similar mechanism involving the iris and the sphincter muscle, although it is not clear which of these is of greater importance in molding the lens. All four of these reports describe the iris as being pressed against the lens, and two of them note that the conoid form of the lens appears to be the result of bulging through the pupil. Could the iris play a major role in accommodation after all? This may appear too speculative to be taken seriously, yet the iris/lens mechanism is well documented in certain birds and mammals. According to Walls, "The avian iris is always of material assistance during accommodation in holding back the lens against which it presses, and in inhibiting the peripheral part of the anterior surface of the lens from bulging, thus concentrating the change-of-curvature in the part of the surface opposite the pupil." (18) Posterior and interior lens changes However, the conventional wisdom that the principal changes occur in the anterior lens was challenged by Patnaik, who wrote that "...the often stated and commonly accepted statement, that it is the anterior lens surface which moves forward while the posterior surface remains stationary and that it is only the anterior surface which changes its curvature during accommodation seems not to be correct. "Our observations strongly indicate that during accommodation the increase in the thickness of the anterior cortex is minimal, and that the change in the posterior cortex is greater, and that in the nuclear thickness change is greatest." (26) This last may be especially significant because it raises the possibility that the principal source of increased lens power in myopes could be the nucleus. Young also commented on the importance of the posterior surface: "The pressure changes in the vitreous chamber may also play a role in the process of accommodation, since the back lens surface could be molded by the increase in pressure more effectively than the front lens surface. Unpublished phakometric studies now indicate that the back lens surface contributes almost twice as much to the total vergence of light and is second only to the cornea in its refractive power. The attachment of the hyaloid membrane to the back lens surface may play a major role in the development of the greater lens power of the back lens surface. There is some evidence from children (sic) phakometry that the back lens may have several curvatures rather than the simple, monotonic curve of the front lens surface." (27) Otsuka commented on the difficulty of studying the back of the lens: "...the exact radius of the posteior lens surface is impossible to determine because of the lack of knowledge regarding the internal change of the lens substances." (34) The Lens Capsule In regard to the conoidal form of the anterior lens surface, when Helmholtz first proposed his relaxation theory of accommodation it was criticized on the ground that relaxation of the zonule failed to explain how this molding was achieved. Tscherning claimed that this could only be produced by pressure from the vitreous, which he believed molded the softer cortex of the lens around the harder nucleus. Fincham thought he found an answer in evidence that the thickness of the lens capsule varies, and he believed that these minute differences in thickness were sufficient to impose a conoidal shape on the anterior surface of the lens (14). Although it is conceivable that the capsule could mold the lens to a slight degree in this manner, the evidence from my own experiment indicates that this explanation is insufficient. Because the degree of spherical aberration was undoubtedly so extreme, which indicated extreme flattening of the periphery of the lens, it is difficult to believe that it could have been produced by such minute differences in capsule thickness. In fact, the contrary could be argued just as persuasively: that the differences in capsule thickness could be the RESULT of pressure on the lens. The thin segment of the capsule in the anterior axial area could be caused by stretching of the capsule, while the thin posterior segment could be caused by the vitreous squeezing the capsule against the lens. The Extraocular Muscle Hypothesis The hypothesis that the extraocular muscles play a role in the causation of myopia is certainly not new. It has been suggested by numerous investigators over the years. A major difference, however, is that in none of these hypotheses has it been proposed that they have any effect on the lens. All are limited to the concept of elongation of the globe, usually through elevation of the intraocular pressure. The case is similar with regard to the numerous hypotheses that propose contraction of the ciliary muscle as a cause of myopia. They all postulate that such contraction elongates the globe, and do not suggest any effect on the lens. The Persistence of Accommodation and the Etiology of Myopia A significant feature of the experiment was the amount of time in which the lens was subjected to pressure and, as I believe, accommodation. An eye whose lens remains accommodated will show blurred vision for distance gaze. But the lens is not supposed to remain accommodated when the stimulus for accommodation is removed. According to orthodox theory, accommodation is maintained only as long as the gaze is directed at a near object. When the gaze is shifted to a distant object, the lens reverts almost immediately to the unaccommodated form required for distance vision. The consensus of opinion is that these accommodative changes take about one second. I believe that this view is probably a result of too much reliance on laboratory studies that deal only with momentary accommodation, and that there is a crucial difference between momentary and repeated prolonged accommodation. The persistence of dual vision in my own case, as well as the findings of a number of investigators on the slowness of lens changes, leads to the conclusion that the longer a lens is maintained in a particular form, the longer it takes to return to its original form when released. Further, with high degrees of deformation the lens does not return entirely to its original form. In my case, the sharp image persisted for more than four years before it gradually began to disappear. I assume that this was due to a gradual decrease in the degree of flattening of the periphery when the pressure was removed. Since the blurred component of the image remained largely unchanged, apparently this was because the central region of the lens changed very little. On the question of the slowness of lens changes, there is support from other investigators. Lancaster states that "...if the accommodation is maintained a few minutes at the maximum, the near point does get nearer and the eye may become accommodated 20% to 30% or more, nearer than at the first. If the near point at the start was 6 D. it may become 7, 8, or 9 D. This...is due to the viscosity of the lens substance. An immediate rapid (about one second) change takes place when the lens adjusts itself for a near object, but if a maximum effort of accommodation continues to be made, the lens slowly (5 to 10 minutes) goes on changing its shape and becoming more strongly refractive. "Commonly, when the eye, after such an intense effort of accommodation, is shifted to a distant object, although the ciliary muscle may promptly relax, it takes time (a few seconds to a few minutes depending on how long the near effort was continued) for the lens to regain its normal shape adapted to a distance. This is due to the viscosity which makes a change in the shape slow." (19, pp. 115-116) Other investigators have also demonstrated the slowness of lens changes. According to Kikkawa and Sato, "Application of an external force to the lens caused a rapid deformation followed by a second phase of slow deformation. On removal of the force, a rapid partial reversal of the deformation occurred and was followed by a gradual restoration; complete recovery was not achieved." (20) Kabe reported a similar result from his investigations. He showed that when accommodation is increasing, the change in the apparent curvature of the anterior surface of the lens is slow and continuous, but when accommodation is decreasing, there is a prompt, followed by a slow phase. (21) The idea that myopia could be the result of increased lens power has always been countered by a strong argument. If in myopic eyes the lenses are permanently accommodated, they would tend to be thicker than the lenses of emmetropes. Not only is this not true, but, in general, myopic eyes tend to have even thinner lenses than emmetropes. As far as myopia is concerned, there is a clear consensus of opinion as to the importance of the lens: It ranks very low: "Three variables, then, the axial length, the shape of the cornea, and the power of the crystalline lens, exert the greatest effect upon refraction. There is good agreement among authors as to the relative influence which each of these exerts, the axial length being the greatest, followed by the cornea and lens in that order. There are minor disagreements among investigators as to the relative importance of the least of these three elements, the crystalline lens: Van Alphen's work suggests perhaps the lowest estimate of the importance of the lens. However, all investigators arrive at the same order of importance, and at relative values not too different from those obtained by others". (22) Sorsby seemed to be puzzled by the existence of thin lenses in myopes and tried to find a way out of the difficulty be speculating about the tension of the zonule. He stated that, "Obviously, a large fairly spherical eye will have not only a long anteropsterior axis but also a flatter cornea. Flattening of the lens in a large eye is more difficult to understand, but a more marked tension on the suspensory ligaments may be a possible factor." (23) The barrier to a resolution of this contradiction seems to be the belief that a thin lens can not be an accommodated lens. But if the slowness of lens changes is correct, and there seems to be no dispute about this, then in myopes the lens MUST be accommodated. Consider the case of a myope with a history of nearwork, e.g. with hour after hour of reading over months and years. It could very well be that with repeated periods of prolonged accommodation the lens, with its slow reaction time, would never return completely to the unaccommodated state. The conventional argument that the lenses of myopes are not only not of the same power as emmetropes, but are of even lower power, is illogical. The possibility that a lens subjected to frequent prolonged accommodation for months and years may not have the same shape as a lens that is accommodated only briefly apparently has not been considered. The hypothesis of vitreous pressure suggests that such prolonged pressure might produce a lens with a flattened periphery but with a high degree of curvature in the axial region, i.e. a lens that is thin yet accommodated. I have found only one reference in the literature that even indirectly supports this hypothesis. In a study of accommodation, Otsuka stated that "the thicker the lens became during accommodation, the thinner the lens became annually." This is intriguing, but unfortunately he did not elaborate. (24) It may be that a single factor, external pressure on the globe, produces two separate effects, in opposite directions: anteriorly it accommodates the lens, and posteriorly it elongates the globe. I believe that one consequence of this dual effect is that axial elongation has masked the role of the lens. With such a logical and easily demonstrated explanation available, there has been little incentive to look for an additional factor, and thus the lens has been practically ignored. The indications that external pressure had produced accommodation by forcing the vitreous against the lens suggests the possibility that the vitreous plays a part in normal accommodation, i.e. that the experiment mimicked what happens in normal accommodation. It is possible that in normal accommodation, contraction of the ciliary muscle pulls the vitreous forward against the lens, again, not a new idea; this was suggested by Cramer in 1851, and later by Tscherning. In the present experiment, however, I believe the vitreous was _pushed_forward by external pressure on the globe. Theory versus observation Curiously, there is a case of photographic evidence that the lens becomes thinner with accommodation, even momentary accommodation. This appears in a paper by Burian and Allen which shows photographs of the lens during three stages: 1) Relaxation of accommodation; 2) Active accommodation; and 3) Active accommodation (apparently further). However, instead of showing that the lens thickens with accommodation, it shows precisely the opposite. In each photo-graph it can be clearly seen that the lens becomes progressively thinner, at least in the peripheral area. These photographs are reproduced in Duke-Elder's System of Ophthalmology (25, p. 163--possibly different pages in other editions) and in a more recent work by the late David Michaels, Visual Optics and Refraction. (5, p. 184) Nevertheless, except for noting the flatness of the posterior surface of the lens, none of these authors comment on the striking fact that the lens clearly becomes thinner as it accommodates. In fact, in the text preceding the photographs, Duke-Elder states: "All are agreed that the lens increases in thickness during accommodation" (!). It seems that theory is more potent than direct observation. An additional note on this photograph: Burian and Allen state that "our observations on the periphery of the vitreous surface strongly suggested that the vitreous body, far from pressing upon the periphery of the lens, was actually under reduced tension during accommodation." They believe that the evidence for this is the bowing back of the vitreous, which they believe creates "an optically empty space in front of the vitreous." They fail to explain how this "optically empty space" could occur. A possible explanation is that this space, apparently the canal of Petit (the space between the zonule and the vitreous) has expanded from an inflow of aqueous under pressure. Johnson demonstrated such an inflow by the use of dyes, and he believed that accommodation was actuated by hydraulic pressure exerted around the periphery of the lens (9). Duke-Elder dismissed this as a "bizarre hydraulic theory," but the opening and closing of the trabecular meshwork by the action of the ciliary muscle does suggest a hydraulic component of accommodation. Lens Changes Hidden If significant lens changes do occur in the posterior surface of the lens, this would be one more example of how the clues to lens involvement in myopia are hidden. Consider the case of a myope who undergoes a routine eye examination. If he has a moderate degree of myopia, the posterior surface of the lens could be flattened just enough to have created a second focal point. However, the examiner would never discover this for two reasons: He will probably not look for something whose existence he is unaware of; and because the second focal point would not reach all the way to the retina, no clear secondary image is formed. Only with a particular lens power which would push the secondary focal point to the retina would a clear secondary image be formed. Additional Secondary Images In order to simplify this discussion, I have limited it to the primary and secondary focal points and their images. Actually, however, testing of myopes with different lens powers reveals that there are often other images, fainter "ghost" images that are more difficult to detect, which indicate the presence of other focal points situated between the primary and secondary focal points. The origin of these could be the various isoindicial surfaces within the lens. Some high myopes, when tested with various lens powers, describe not a smooth, diffuse blur, but rather several superimposed blurred images. Although I didn't appreciate it at the time, it was fortunate that the first subject for the experiment was myself. What if I had found a willing emmetrope, or a subject with only a small degree of myopia? The outcome would probably been very different. The experiment would probably produced a small degree of myopia, partly from axial elongation and partly from lens changes (just as I believe occurs in normal myopia). The significant point, however, is that I would never have suspected the lens, but would have attributed the myopia to axial elongation alone. Because I was a myope of fairly high degree, I believe that flattening of the periphery of the lens was fairly well advanced, so that the secondary focal point was already located very close to the retina. It then required very little additional flattening to push it all the way, or very close to, the retina, at which time I became aware of the secondary image. A laymen who reads textbooks on ophthalmology can easily get the impression of a solid edifice of knowledge built on firm foundations. Yet at least one researcher, Ludlam, suggests that some of the most basic facts about the eye are based on faulty data and should be re-evaluated. These include invalid mathematical assumptions, mixed sampling, inadequate experimental technique, and oversimplified models of the refractive system, some of these dating from the nineteenth century: "Nevertheless, the analyses and conclusions drawn from such studies can be no better than either the methods of acquisition of the basic data or the validity of the assumptions underlying the mathematical formulation of the ocular model. "It is well to note that in all of these studies the model of the ocular system utilized has consisted of: 1. Spherical refracting surfaces, causing a systematic under-estimation of the paraxial refracting power of each surface. ----- 5. A homogeneous monoindicial lens. This places a high order of importance on the accuracy and precision of the measures of curvature of both the anterior and posterior surfaces of the lens and concomitantly increases the potential effects of spherical assumption. " In addition, in none of these studies have all the refractive components of any given eye been measured. There has always been _at least one_ component whose value was calculated from the other measured elements, so that the measurement errors would all tend to accumulate in the non-measured element. Since the measurement errors have not always been stated with sufficient clarity to enable the effects of these errors to be assessed, the probability exists that measurement errors have contributed substantially to spurious correlations of measured and calculated elements, as for example between the lens and axial length." (29) To say that long-standing theories are not easily overturned is to state the obvious. As Kuhn put it, "...few scientists will easily be persuaded to adopt a viewpoint that again opens to question many problems that had previously been solved" (30, p. 169). Ophthalmology is no exception, and scattered reports in the literature that cast doubt on the conventional wisdom, for just one example, an interesting case described by Luedde (31), are simply ignored. How Not to Cure Myopia The lens/vitreous hypothesis provides an explanation for the failure of two therapeutic measures aimed at preventing or slowing the progress of myopia: the use of cycloplegics, and base-in prisms. In the case of cycloplegics, they relax the ciliary muscle for only a few hours at a time, while the lens requires many months for a significant reduction in the degree of accommodation. More importantly, in all these regimens the subjects are permitted to continue doing nearwork, so that accommodation could still have been maintained largely by vitreous pressure alone. The use of base-in prisms to prevent convergence, and consequently accommodation has, I believe, failed for an unsuspected reason: the optical distortion inherent in such prisms. I used base-in prisms extensively in various experiments aimed at reducing accommodation and was surprised to find that in some cases the degree of myopia _increased_. Strong base-in prisms produce considerable distortion, and a possible explanation is that in trying to fuse the distorted images, the eyes were forced to incyclorotate in antagonism to each other, and this in turn required the superior oblique muscles to maintain contraction as long as the image was fused, thereby exerting pressure on the globe and maintaining accommodation. The vitreous/lens hypothesis might also shed some light on other unresolved questions in ophthalmology, e.g. the increase in accommodation when the eyes converge, and ametropia related to extraocular muscle imbalance. It might also explain why myopes tend to have underdeveloped ciliary muscles: if the lens is more or less permanently accommodated, the ciliary muscles would have less need to function. Scientific Error It is highly unlikely that such well-established concepts as the theory of accommodation and the role of the crystalline lens could be wrong. The relaxation theory is extremely well documented and for more than forty years has been considered the only acceptable explanation of how the eye accommodates for near vision. The possibility that many researchers in many different countries could be wrong about such a basic theory will not be taken seriously. Nevertheless, there have been a few cases of major reversals of scientific opinion. The case of nervous system plasticity provides a good example. For more than fifty years it was universally believed, and confirmed by hundreds of experiments by reputable scientists, that the plasticity of the central nervous system allowed any muscle nerve to be reconnected to any other muscle and, with training, achieve full restoration of function. it is now known that this is not true. According to R.W. Sperry, "During the past 15 years, however, scientific and medical opinion has undergone a major shift, amounting to an almost complete about-face ... The evidence for this view, which comes from new experiments and exacting clinical observations, is so persuasive that it is difficult to understand how the opposite view could have prevailed for so long. It appears that most of the earlier reports of the high functional plasticity of the nervous system will go down in the record as unfortunate examples of how an erroneous medical or scientific opinion, once implanted can snowball until it biases experimental observations and curshes dissenting opinions...Hundreds of experiments seemed to support the now-discounted opinion..." (28). I propose that a similar case has occurred in ophthalmology. CONCLUSION 1. An experiment in long-term compression of the globe of the eye created monocular diplopia, seen as two separate images superimposed, one on the other. 2. It is hypothesized that the cause of this effect was the spherical aberration of the crystalline lens resulting from pressure of the superior oblique muscles transmitted through the sclera, which forced the vitreous forward, pressing it against the posterior surface of the lens. 3. This suggests a role of the vitreous in normal accommodation, i.e. that ciliary contraction pulls the vitreous forward to mold the lens. 4. This vitreous-mediated accommodation may be enhanced by additional compression from the vitreous from an external source, the action of the extraocular muscles. 5. The extremely slow changes in lens shape strongly implicate nearwork in the etiology of myopia. Because of the slowness of recovery from accommodation, long periods of accommodation with insufficient intervals of rest result in a lens that becomes permanently accommodated. The accommodated state of the lens may be additionally enhanced by the action of the extraocular muscles in nearwork, particularly reading. 6. The argument that myopic lenses are not accommodated because they tend to be thin could be explained by long-term compression. This could produce an accommodated lens with either a flattened periphery and convex axial region, or a thin lens with accommodative changes in the nucleus. Although the lens/vitreous hypotheses doesn't resolve all problems, I believe it resolves some, and anyway, as Kuhn points out, "no paradigm ever solves all the problems it defines and since no two paradigms leave all the same problems unsolved, paradigm debates always involve the question: Which problems is it more significant to have solved?" (30, p. 110). It is interesting to consider the extent to which a mistaken theory is a barrier to solution of a problem, and how a new point of view can open up previously unconsidered possibilities. These possibilities could include not only finally determining the etiology of myopia, but could include prevention, or even cure. Donders expressed the pessimistic view more than a hundred years ago: "The more our knowledge of the basis of this anomaly has been established, the more certainly does any expectation (of a cure) appear to be destroyed, even with respect to the future" (32, p. 415). Today, probably most eye researchers would share this view. If the hypothesis of oblique muscle/vitreous/lens connection is confirmed, it could open the way to new techniques to prevent or slow the progression of m/lens connection is confirmed, it could open the way to new techniques to prevent or slow the progression of myopia. Further, it is not impossible that a cure for myopia could be devised if a a way could be found to effectively prevent accommodation and convergence while performing nearwork. A less desirable approach would be the use of invasive techniques to reshape the curvature of the lens. Common sense is often an unreliable guide in science. Nevertheless, it may apply here. It would be curious if, after the tremendous amount of work and speculation on the causes of myopia, the answer turned out to be, in the end, a simple one: "In myopia, the lenses are permanently adjusted for near vision." Richard McCollim Appendix A. As far as I know, the debate on the etiology of myopia between those who claim a genetic basis and those who point to environmental causes still favors the former. Nevertheless, the reports of a relationship between nearwork and myopia should not be ignored. No one would dispute that the most common form of nearwork and the most "unnatural" use of the eyes is reading. Because the continuous horizontal scanning movements of the eyes in reading with downward gaze require alternate contraction and relaxation of the oblique muscles, I decided to simulate this condition in an enhanced form to determine if such contraction could produce elongation of the globe. (Actually, the axial elongation theory is an oversimplification, in that it fails to explain, for example, normal vision in elongated eyes and myopia in relatively short eyes. The investigations of Steiger (2) and others produced a shift in emphasis to the question of the variability of the different ocular components and how they interact with each other to produce emmetropia--absence of a refractive error--or ametropia--presence of a refractive error). Because the eye muscles are not subject to individual voluntary control, it was necessary to devise some means to force the superior obliques to contract while maintaining relative relaxation of the other extraocular muscles. I thought that the natural tendency of the eyes to fuse to disparate images could be utilized for this purpose. I constructed a viewing device which contained two identical photographic transparencies depicting a visually rich pattern. When the subject looked through the device, each eye viewed one of the transparencies; the visual cortex then fuses the two images to form a single scene. The transparencies were then incyclorotated, i.e. as seen by the subject, the right-side image was rotated counterclockwise and the left-side image was rotated clockwise. In order to maintain fusion of the two images, each eye must then rotate in the same direction as the image it is viewing, i.e. the upper end of the vertical meridian of each eye leans nasalwards. The movement of incyclorotation is effected principally by the superior oblique muscles, but there is a limit as to how far the globe can rotate, since this is opposed by the check ligaments and other fascial structures of the orbit. If an effort is made to maintain fusion, the traction of the superior obliques, which wrap part way around the globe, will exert pressure in the general area of the equatorial meridian. The device was later modified for portable use to facilitate long-term viewing. Instead of viewing transparencies, the subject looked through a system of mirrors that tilted in like manner any scene viewed. The amount of tilt (incyclorotation) varied between 6 and 12 degrees. This is not to say that if the images are rotated, say, 8 degrees, each eye will also rotate exactly 8 degrees; eye rotation can be as much as 2 degrees less. This is because of Panum's fusional area, which in stereopsis allows the image to be pulled apart by some 2 degrees before being broken up into two separate images. The images are actually pulled apart on the retina, but a supra- retinal function maintains perception of a single image (33). In order to eliminate any stimulus to accommodation, distance fixation of at least six meters was maintained. Because I was unable to make axial length measurements, I had to rely on changes in the visual acuity to determine if there had been any changes in axial length. Thus, if my visual acuity began to deteriorate in the course of the experiment, this could be an indication that the globe had elongated, presumably due to compression of the globe by the superior obliques. Appendix B. Spherical aberration Spherical aberration is that condition in which the rays passing through a convex lens do not all come to a focus on a single point. Ivanoff (4) and others have shown that spherical aberration is normal in the human eye. When the eye is ate rest the spherical aberration is positive, which means that the rays passing through the periphery of the lens come to a focus in front of rays passing through the axial region of the lens. 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