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V. Choh, M. Yi, C.F. Wildsoet; Effects of Interchanging Form-deprivation and Incremented Hyperopic Defocus Stimuli on Normal and Optic Nerve-sectioned Chick Eyes . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1992.
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Purpose: In chick eyes, interchanging diffusers and -15 D lenses does not affect vitreous chamber elongation relative to either device alone, while in optic nerve-sectioned (ONS) eyes, diffusers induce the greatest response and -15 D lenses, the least. Together, these results suggest that the mechanisms underlying form deprivation- and lens-induced myopia may differ in ONS-eyes. This study was undertaken to investigate the possibility that -15 D lenses induce deprivation cues in addition to, or instead of, defocus cues. Methods: One eye of normal, and the operated eye of optic nerve-sectioned, 11 day old chicks were fitted with either a diffuser or a -5 D lens, and for a subset, the two devices were interchanged at 3 hr intervals across each 12 h-day. To prevent full compensation to -5 D lenses, -5 D lenses were replaced by -10 D lenses after 30 h and -15 D lenses after 69 h. Measurements were made on both eyes prior to goggling and after 4 days using an autorefractor for refractive errors (RE) and high frequency A-scan ultrasonography for axial ocular components. Results: Mean interocular changes (± sd) View OriginalDownload SlideView OriginalDownload Slide Conclusions: As in experiments with -15 D lenses, form-deprived ONS-eyes showed the greatest change, while no device-specific effects were observed in normal eyes. These findings suggest that the mechanisms mediating deprivation- and lens-induced myopia were altered in ONS eyes. ONS disconnects the accommodative loop, removes centrifugal input retina and causes inner retinal cell loss. One or more of these factors may underlie the effects observed.
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