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Earl L. Smith, Li-Fang Hung, Chea-su Kee, Ying Qiao; Effects of Brief Periods of Unrestricted Vision on the Development of Form-Deprivation Myopia in Monkeys. Invest. Ophthalmol. Vis. Sci. 2002;43(2):291-299.
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purpose. To characterize the temporal integration properties of the mechanisms
responsible for form-deprivation myopia (FDM), the effects of brief
daily periods of unrestricted vision on the degree of FDM were
investigated in infant monkeys.
methods. Starting at approximately 3 weeks of age, unilateral form deprivation
was produced in 24 infant rhesus monkeys by securing a diffuser
spectacle lens in front of one eye and a clear, zero-powered lens in
front of the fellow eye. During the treatment period (17 ± 2
weeks), six infants wore the diffuser lenses continuously. In the other
experimental infants, the diffuser lenses were removed each day and
replaced with clear, zero-powered lenses for 1 (n = 7),
2 (n = 7), or 4 hours (n = 4). Refractive
development was assessed by retinoscopy and A-scan ultrasonography.
Control data were obtained from 11 normal infants and 3 infants reared
with zero-powered lenses over both eyes.
results. The degree of FDM varied significantly with the duration of
unrestricted vision. Continuous form deprivation produced −5.2 ±
3.6 D of relative axial myopia. However, 1 hour of unrestricted vision
was sufficient to reduce the degree of axial FDM by more than 50%
(−1.7 ± 3.2 D). The infants that were allowed 4 hours of
unrestricted vision exhibited only −0.4 ± 0.5 D of FDM.
conclusions. As observed in chickens and tree shrews, relatively long periods of
form deprivation can be counterbalanced by quite short periods of
unrestricted vision. These results indicate that the processes or
signals that promote axial elongation in monkeys are comparatively weak
or easily overridden by factors that slow ocular
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