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R. A. Schuchard, G. Dagnelie, J. Pollack, J. Kotowski, A. Chow, ASR® Device Study Group; Evaluation of the ASR DeviceÂ® for the Treatment of Vision Loss From Retinitis Pigmentosa: Phase II Study. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4445.
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To evaluate visual acuity and other outcome measures in people with RP implanted with the subretinal ASR device.
20 subjects were implanted with the ASR device after baseline measures were obtained. Subjects were 32 to 69 years of age, had 20/80 to 20/1600 visual acuity in the implanted eye, randomized to left and right eyes in equal numbers, and fellow eyes as control. Subjects were tested at 3-month intervals during the second year of follow-up with 12, 15, 18-month second year pooled results reported. At the one-year evaluation, the results indicated that there were two confounding factors; dilation during vision testing and cataract progression. These confounding factors increased glare and reduced contrast sensitivity, which potentially impacted visual function outcome measures in some subjects. Therefore, data from a subset of subjects (10) who had at most one confounding factor were analyzed separately. Outcome measures included visual acuity, visual fields, controlled mobility ratings, everyday function and quality of life self-report (VA LV VFQ-54) and mobility ability self-report (Turano questionnaire). Responders are reported based on the variability in repeated testing of patients with RP (e.g., 7 letters for visual acuity) as a measure of clinical significance.
At 18 months post-implantation with 2 subjects lost to follow-up, 6/3 of 18 (33%/17%) implanted eyes had significant improvements/declines in visual acuity while 1/3 (6%/17%) fellow eyes had significant improvements/declines in visual acuity. In the subset of 10 subjects with one or no confounding factor, the same subjects had improvements in visual acuity (6/1, 60%/10%, in implanted/fellow eyes) while no subjects had significant declines in visual acuity. The other outcome measures had similar results and additional confounding factors (e.g., increased variability in visual fields results and difficulty of determining ability to do everyday tasks on visual function alone). Adverse events to date have not been related to the chronic presence of the ASR Device.
Based on the second year pooled results, the ASR Device can produce improvement in visual acuity and other measures when the confounding factors are controlled. The previously postulated neurotrophic mechanism appears to improve the function of existing photoreceptors. Twenty-one month and two-year post-implantation data, available by March 2007, will be presented in an updated analysis.
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