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[Effect of time limited form deprivation on the development of myopia in guinea pigs].

OBJECTIVE
To investigate the effect of time limited form deprivation on the development of form-deprived-myopia (FDM) in guinea pigs.


METHODS
Four-week-old guinea pigs (n = 20) were randomly divided into four groups. Group I was used as normal control without any treatment. In group II-IV, unilateral form deprivation was produced with eye patch for 4 weeks. In group II, eye occlusion was fitted continuously. In group III and IV, occlusion was removed each day for 1 or 4 hours. Refractive development was monitored by retinoscopy and A-scan ultrasonography before and after experiment.


RESULTS
After 4 weeks, varied degree of axial myopia was developed in the groups II and III with eye occlusion. Continuous form deprivation produced -5.49 D of relative myopia and the fellow eyes produced +0.76 D of relative hyperopia. One hour of unrestricted vision was sufficient to reduce the degree of FDM by about 50%. The eyes allowed 4 hours of unrestricted vision did not result in myopia.


CONCLUSION
Long periods of form deprivation can be counterbalanced by quite short periods of unrestricted vision.