The very common ocular clinical ocular condition in children juvenile onset myopia results from axial elongation of the eye. In humans, some studies have found an association of myopia with greater levels of nearpoint activity and with differences in accommodation and convergence function. This paper reviews a variety of laboratory and clinical studies which are consistent with the hypothesis that retinal image defocus is biochemically transformed into an axial elongation expressed through increased posterior segment growth, and thus myopia. This paper also reviews theories of emmetropization, and classifies them as correlational, feedback, and combination. Evidence is presented to suggest that a combination theory, which combines both correlation of the ocular dioptric components and some feedback mechanism for growth of the eye, is the most correct. Current laboratory research suggests that quality and/or focus (defocus) of retinal imagery is involved in this feedback mechanism and that experimentally induced myopia might be enhanced, reduced or eliminated by pharmaceutical application. Direction of defocus may affect the rate of posterior segment growth, and thus the rate of ocular axial elongation.

A study of the structure and distribution of encapsulated corpuscles (corpuscles of Rochon-Duvigneaud) in the irido-corneal (anterior chamber) angle in 42 adult eyes from nine species of odontocete cetaceans representing each of the five families in this group indicates a diversity of form and function. The corpuscles occur as signle features or multiple groupings with each species having a distinct pattern. No definite phylogenic or environmental patterns were seen although sometimes there were similarities among related genera. The neural structure of the angle suggests that these receptors probably respond to a variety of stimuli including intraocular pressure, vitreous displacements, external muscular force applied to the sclera and cornea, and changes in the volume of the massive iris/choroid vascular system.

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