The degree of image degradation and the depth of amblyopia

PURPOSE: To determine whether the depth of monocular form-deprivation ambly opia is dependent on the degree of retinal image degradation. METHODS. Chronic monocular form deprivation was produced in nine infant rhe sus monkeys by securing one of three different strengths of diffuser specta cle lenses in front of the treated eye and a clear zero-powered lens in fro nt of the fellow eye. Three infant monkeys reared with piano lenses in fron t of both eyes provided control data. The treatment lenses were worn contin uously from approximately 3 weeks of age for periods ranging between 11 and 19 weeks. When the monkeys were approximately 18 months of age, psychophys ical procedures were used to measure the effects of the rearing procedures on the spatial contrast sensitivity function for each eye. RESULTS. The treated eyes of all nine diffuser-reared monkeys showed contra st sensitivity deficits that were indicative of amblyopia. On average, the interocular grating acuity difference increased systematically from 0.6 oct aves for the weakest diffuser lens to 2.3 +/- 0.7 and 3.5 +/- 0.8 octaves f or the intermediate and strongest diffuser lenses, respectively. There was a close correspondence between the magnitude of the amblyopic deficits and the reduction in retinal image contrast produced by the diffuser lenses. CONCLUSIONS. The results demonstrate that the depth of monocular, nonstrabi smic amblyopia is strongly influenced by the degree of retinal. image degra dation experienced early in Life.