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C.E. Stewart, M.J. Moseley, A.R. Fielder, D.A. Stephens, ROTAS Cooperative; Optimization of the Dose–Response of Occlusion Therapy for Amblyopia: the ROTAS study . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2579.
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Purpose: To compare changes in visual function occurring in response to two prescribed occlusion dose rates: 'substantial' (6 hours per day) and 'maximal' (12 hours per day) in the Randomized Occlusion Treatment for Amblyopia Study (ROTAS). Methods: Data were obtained from 42 participants (mean age = 5.5 ± 1.5 years) with amblyopia associated with strabismus (n=11), anisometropia (n=19), and both anisometropia and strabismus (n=11). Forty–one participants required refractive correction and underwent 18 weeks of spectacle wear ('refractive adaptation') before undergoing occlusion. Those participants whose amblyopia persisted were randomized to either 6 hours (n=22) or 12 hours (n=20) occlusion per day. Outcome variables (logMAR visual acuity, log letter contrast sensitivity [Pelli–Robson] and vernier acuity) were assessed at six–weekly intervals during refractive adaptation and at weekly intervals during occlusion until gains ceased to be statistically verifiable. Patch wear was objectively recorded using an occlusion dose monitor (Fielder AR, et al. Lancet, 1994;343:547). Results: Forty–two children entered the occlusion phase and were randomized to the prescribed occlusion regimens. Changes in visual acuity for the 6 hour group (0.26 ± 0.18 logMAR) were not significantly different (p=0.56) from the 12 hour group (0.25 ± 0.29 logMAR). However, the mean total dose worn and dose rate to achieve the best visual acuity were not significantly different (p=0.20 and p=0.08 respectively) for the two groups: mean total dose (hrs) in 6 hour group = 229 ± 126, 12 hour group = 309 ± 264; mean dose rate (hrs/day) in 6 hour group = 4.19 ± 1.7, 12 hour group = 5.89 ± 4.13). Children were then grouped according to dose rates (hrs/day) actually worn: 0–3 (n=13), >3–6 (n=17) and >6–12 (n=11). Significant differences (p=0.009) in observed changes in visual acuity were shown between the 0–3 group and the >6–12 group (change in logMAR visual acuity of 0–3 group = 0.17 ± 0.17, >3–6 group = 0.26 ± 0.21, >6–12 group = 0.36 ± 0.18). Conclusions:'Substantial' (6 hours/day) and 'maximal' (12 hours/day) prescribed occlusion dose rates provide equivalent improvement in visual acuity for the treatment of amblyopia in children 4 to 7 years of age. However, concordance for maximal doses is relatively poorer than for substantial doses. Monitoring actual doses received using occlusion dose monitors reveals that children receiving considerable doses show significantly more improvement than those in receipt of minimal amounts.
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