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H.M. Bowie, A. Bittner, A. Chow, G. Dagnelie, ASR Study Group; Repeatability of Projected MNRead Tests in Advanced Retinitis Pigmentosa Subjects . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4588.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To establish test–retest repeatability of projected MNRead test with software developed by Optobionics Corporation, prior to implantation of an Artificial Silicon Retina (ASR TM ) device. Methods: Pre–operative data were collected from 20 subjects across four centers at two office visits. At the start of the first session, polarity of the text (black–on–white vs white–on black) was determined based on subject's optimal performance. Text sizes cover a .6 log units span, in 0.1 1.u.steps, in the 20/40–20/1600 range. Test distance was 0.5, 1 , or 2m, depending on the pre–op distance visual acuity. Testing was done under full cycloplegia and refractive correction for the test distance. Testing was done for each eye separately, and for both eyes. Measurements included number of correct words, number of words corrected after initial error, and reading time; from these we computed % error and reading speed as a function of log print size, and from the latter, maximum reading speed and critical print size, i.e., the minimum print size at which reading speed exceeds 90% of the maximum. Results: Preliminary analysis of the results from 5 subjects(10 eyes)at the Wilmer site .We defined the better eye as the one with the higher maximum reading speed, which ranged from 1.9 to 84.3 w/min ; with a geometric mean (gmmean) of 17.4 w/min. The log critical print size for the better eye ranged from 1.1 to 1.9 ( ∼20/250–20/1600) The maximum reading speed for the worse eye ranged from 1.2 to 77.7 w/min (gmmean= 6.6), and log critical print size from 1.3 to 1.8 (∼20/400 to 20/1250). Maximum reading rate for both eyes ranged from 2.9 to 77.1 w/min (gmmean=19.7), and log critcal print size d from 1.2 to 1.8 (20/320 to 20/1250). The mean between visits 95% coefficient of repeatability (CR.95) in maximum reading speed was 90% in the better eye, 76% in the worse eye, and 137% in both eyes. The CR .95 of critical print size is .17 1.u. in the better eye, .30 1.u. in the worse eye, and 0.36 1.u in both eyes. Conclusions: The projected MNRead test data show that critical print size, even in readers with poor visual acuity and low reading speeds is highly reliable (2–3 lines needed to demonstrate change), while maximum reading speed shows much greater variability. The projected MNRead test is a useful addition to repertoire of low vision reading tests, as it expands the range to very low visual acuities.
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