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SA McFadden; Partial Occlusion Produces Local Form Deprivation Myopia in the Guinea Pig Eye . Invest. Ophthalmol. Vis. Sci. 2002;43(13):189.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Myopia and axial extension readily results from deprivation of patterned visual input in a growing eye. In the chick model, the control processes are known to be locally contained within sectors of the eye, since myopia can be produced locally when the visual field is partially occluded1. We have developed a model of myopia using the pigmented guinea pig (see Howlett and McFadden, ARVO, 2002), and asked the question as to whether form deprivation myopia is locally controlled in this mammalian model. Methods: Thirty guinea pigs were raised with translucent semi-spherical diffusers over one eye from day 1-35. Diffusers covered either the upper, lower or whole visual field of one eye in different groups. Upon removal of the diffuser, refractive error was mapped in different sectors of the visual field under cycloplegic conditions in animals held in a perimeter device. Eyes were subsequently enucleated and eye shape analysed from digitised images taken of mid coronal cuts in fresh eyes quickly frozen without eye distortion. Results: Eyes that were fully occluded developed axial myopia (mean 7.3D, n=9). The fellow eyes of all animals emmetropised to a mean of +1.3D by day 35, and there was little variation between the lower, central and upper visual fields. In contrast, the partially deprived eyes became progressively myopic in the deprived sectors, although the effect was more noticeable in those animals that had worn occluders in the lower visual field (up to 10D). Similarly, eye shape was effected, such that posterior nodal distances were increased in the deprived sectors of the retina. Conclusion: Partial form deprivation of a sector of the visual field results in local myopic refractive errors and local increases in the radial diameter of the corresponding sector of the eye. 1. Wallman J et al (1987) Local retinal regions control local eye growth and myopia. Science, 237: 73-77.
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