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To claim that myopes don't see well because their eyes are permanently focused for near vision will be considered preposterous. It is impossible that such a fact could have eluded generations of eye researchers, yet there is impressive evidence that this is indeed the case.
The universally accepted view is that the lens can't be the cause because, among other facts, if it were true, myopia could be cured by simply instilling a cycloplegic. This would allow the ciliary muscle to relax and so enable the eye to re-focus for distant vision.
Additional evidence is the fact that the crystalline lenses of myopes tend to be thin, the opposite of what would be expected if the lenses were accommodated for near vision.
Furthermore, everybody "knows" that myopia is caused by the eye being too long:
"The vast majority of myopia which develops during childhood and early adulthood is axial in nature, being produced by an increase in vitreous chamber depth.
"This finding would appear to rule out the proposal that myopia results from the crystalline lens being permanently deformed, i.e. a failure to relax accommodation fully. [How could any rational person conclude that because myopic eyes tend to be long, that that is the SOLE cause of myopia? (My comment)].
"…it must be emphasized that myopia can only be said to exist under conditions of minimal accommodation. If the instillation of a cycloplegic agent eliminates the refractive shift (as will occur in pseudomyopia), then no change in the refractive error of the eye can be said to have taken place." (Rosenfeld, 1998)
Another fatal error-the unfounded belief that accommodation can be eliminated by relaxing the ciliary muscle (e.g. by means of a cycloplegic). There is no question that a cycloplegic will relax the ciliary, but it is wrongly assumed that the lens will then return to its unaccommodated state.
That this is not the case is suggested by the behavior of the eye after a period of prolonged accommodation. This phenomenon, Nearwork-Induced Transient Myopia (NITM) is so well documented as to be beyond dispute (see "The Crystalline Lens in Myopia" on this site).
It is interesting that eye researchers have comeso close to discovering the lens factor, based on NITM, but then veer off on a tangent to the retinal defocus hypothesis, claiming that the myopic shift is caused by a blurred retinal image which triggers a mechanism that causes the eye to grow longer.
In addition, the claim that the lens is not a factor in myopia is demolished by the vibration experiment, also described on this site.
Needless to say, if the lens/myopia hypothesis can be proven, it would be a HUGE embarrassment to the eye research community--which is why it probably won't happen.
Nevertheless, there is a potential solution to this question: replicate the vibration experiment. However, this is probably not feasible, for obvious reasons--principally the ethical problem of possible harm to the subject.
A possible alternative would be to use the enucleated lens of a myope, subject it to vibration and measure changes in shape or structure that might mimic the changes that occur with relaxation of accommodation in a living eye.
The inability of the eye to change its focus due to the inelasticity of the lens is widely accepted as the explanation for presbyopia (the condition that occurs with aging in which the eye cannot focus for near vision), yet the opposite condition, the inability of the lens to focus for far vision because of inelasticity of the lens, resulting from prolonged accommodation, is rejected.
Rosenfeld, M. In: Myopia and Nearwork. P.106 (M. Rosenfeld and B. Gilmartin) Butterworth-Heinemann, p.106