Published in the May, 1975 issue of the AMERICAN JOURNAL OF OPTOMETRY AND PHYSIOLOGICAL OPTICS

ABSTRACT
A new instrument has been developed for utilization in attempts at myopia therapy and control. The inventor discusses instrument design and treatment procedures, and suggests an explanation for the movement of juvenile eyes from hyperopia into myopia.

RATIONALE
The word emmetropization has been used to designate the apparent coordinated or correlated growth of the various structures of the eye. For example, axial elongation during growth would be compensated for by a flattening of both lens and cornea. Myopia, according to this view, develops from failure of compensation.¹ I suggest, on the other hand, a concept of myopia development in which the movement of youthful eyes from mild hyperopia, through emmetropia, and into myopia is seen not as a failure of compensation, but as the normal compensation of the normal eye to excessive close work.

According to Sorsby,¹ the components of the eye attain near-adult size during the rapid growth of the first three years of life - the infantile stage - after which the eye is left somewhat hyperopic. This is followed by much slower growth from the age of three to 13 - the juvenile or definitive stage. I suggest that it is during this stage that the cushion of hyperopia is used by the eye for the final refinements in the vision.

Recent research by Young² suggests that there is a pressure increase in the vitreous chamber under accommodation and convergence, and that this increase in pressure is directly related to the amount of accommodation exerted - the greater the amount of accommodation and convergence, the greater the pressure. It is believed that if this increase in pressure is present over an extended period of time due to a lack of relaxation of the ciliary muscle, an overall enlargement of the vitreous chamber will result as the coats of the eye are stretched and, over a period of time, aqueous fluid moves into the vitreous chamber to fill the increased volume. In tests on monkeys, it was found that a ciliary spasm, once it developed, was usually followed in two to four months by an increase in axial length, thus creating a true axial length myopia.³ Young feels that it is difficult to explain this pressure increase using the Helmholz theory of accommodation, where the ciliary muscle relaxes the tension of the zonule and allows the lens to become more convex. A more compatible explanation is that of Tschering, who claimed that the ciliary muscle, in pulling on the choroid, pressed the vitreous, the ciliary body and the posterior part of the zonule against the lens, which it thus forcibly altered in shape.⁴ According to Coleman,⁵ neither of these two theories of accommodation fully explains how the eye responds during accommodation. The Helmholtz theory does not allow for an active role of the vitreous body, since to do so would apparently contradict the relaxed zonule feature observed during accommodation. The Tscherning theory, on the other hand, largely ignores the features of the relaxed zonule and capsular elasticity. Coleman's model of the accommodative mechanism explains accommodation as a function of both lens elasticity and vitreous support based on analysis of hydraulic forces in the eye, and shows that active vitreous support is consistent with decreased zonular tension, and that the two theories are not contradictory.

On this theoretical basis, it is possible to imagine that a form of ciliary spasm with increased vitreous pressure is meant to occur in the normal hyperopic juvenile eye, since it must accommodate to see clearly even at a distance. The eye thus increases its length because of this pressure until it reaches emmetropia (or near emmetropia), at which time little or no accommodation is needed for distance vision and the full amplitude of accommodation is available for near vision. Many children move through emmetropia into myopia because the constant close work does not permit the ciliary spasm to relax. According to this view, these myopic eyes are reacting normally to their environment. The many children who do much close work but do not move past emmetropia perhaps do not develop a ciliary spasm because they hold the book farther away, or because they look up more often, or for other reasons. The markedly hyperopic eye which does not move toward emmetropia is seen, on the other hand, as an eye which for some reason is not developing properly.

In theory, the development of about 3 D of myopia would enable the uncorrected myope to read without accommodation, and the further progression into myopia would cease. However, if the myopia is corrected with concave lenses, and these lenses are used for reading, the same process could be repeated each time the glasses are strengthened.

Based on the above, and the apparent lack of any evidence that stretching of the coats of the eye can be reversed after it has occurred, an attempt should be made to halt the movement into myopia and return the patient to emmetropia before the myopia becomes more or less permanent. Using the Myopter viewer for as much of the close work as possible is one method of attacking the cause of the ciliary spasm. A similar technique could, of course, be used to try to prevent established myopes from progressing further into myopia.

INSTRUMENT DESIGN
The development of the Myopter viewer was based upon the belief that acquired myopia is caused by an excessive amount of close work, resulting in a ciliary muscle spasm (or, in other words, a change in the relaxation level of accommodation), followed by an increase in axial length. The instrument does not merely treat symptoms, but instead attempts to eliminate the cause.

Since actually eliminating or greatly reducing close work is difficult in our modern literate society, it seemed logical to place an optical system before the eyes that would simulate distance vision to the greatest extent possible whenever close work was to be done. To my knowledge, no such optical instrument was available for this use.

It appeared that accommodation, convergence and stereopsis were the three factors which would have to be closely controlled, since they are normally minimal for distance vision and increase more or less in proportion to each other as the viewed object approaches the eyes. The viewer was designed therefore to reduce these three factors as much as possible.

Ordinary eyeglasses obviously have limitations in simulating distance vision, and can do so only partially. For example, if an emmetropic patient were given +3 D lenses for reading at a distance of 1/3 meter, it would eliminate the need to accommodate for this close work and the ciliary muscles would be in a relaxed condition. However, a substantial amount of positive fusional convergence is required since the normal accommodative convergence is decreased. There appeared to be two major drawbacks to this arrangement. Firstly, it is well known that problems can be created in some patients when the normally present accommodative convergence is decreased to this extent. Secondly, since convergence can stimulate accommodation, it seemed illogical to stimulate the ciliary muscles in this manner when the +3 D lenses had been chosen in an effort to eliminate the accommodation. For this approach, everything possible should be working in the direction of ciliary muscle relaxation. The +3 D lenses could be provided with a base-in prism component strong enough to eliminate the convergence at 1/3 meter reading distance, but a significant amount of "pincushion" distortion is present when using such lenses, and the distortion is more noticeable when the object is viewed with both eyes. Even if such prisms were used with the +3 D lenses, each eye would still see a different view of the object and, for this reason, the eyes would be used in an unnatural manner.