Abstract
Purpose: :
Form deprivation alters the pattern of peripheral refractions and the shape of the posterior globe in infant rhesus monkeys. The purpose of this study was to determine whether the eye can recover from these vision-induced peripheral refractive errors if unrestricted vision is restored following form deprivation.
Methods: :
Monocular form-deprivation was imposed in 10 rhesus monkeys at 3 weeks of age by securing a diffuser spectacle lens in front of one eye. The monkeys wore these lenses continuously until about 150 days of age. Subsequently, the diffusers were removed and the animals were allowed unrestricted vision and each eye’s refractive status was measured periodically by retinoscopy along the pupillary axis and at 15 degree intervals along the horizontal meridian out to eccentricities of 45 degrees. Axial length was determined by A-scan ultrasonography. Control data were obtained from seven normal monkeys.
Results: :
During the diffuser-rearing period, 7 of the 10 treated monkeys developed form-deprivation myopia and interocular differences in central refraction ranging from -2.50 to -10.31 D (average = -6.04 ± 2.68 D; treated eye - fellow eye). All 7 of these treated monkeys also showed relative hyperopia in the periphery that increased in magnitude with eccentricity. Following the removal of the diffuser lenses, there was an obvious decrease in central axial elongation rate and the amount of central myopia decreased systematically over time. At the end of the observation period, the degree of recovery for central refraction ranged from 1.50 to 7.31 D (average = 3.63 ± 1.99 D). In addition, the degree of relative peripheral hyperopia decreased over time, indicating a relative increase in peripheral vitreous chamber depth.
Conclusions: :
Recovery from vision-induced form-deprivation myopia occurs in both the central and peripheral retina. Visual experience can produce alterations in ocular shape that are independent of absolute changes in axial length.
Keywords: emmetropization • refractive error development • myopia