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Luminita Tarita-Nistor, Esther G Gonzalez, Taylor A Brin, Mark Mandelcorn, Anne-Catherine Scherlen, Martin J Steinbach; Fixation stability as a function of viewing distance in patients with AMD. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):544.
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© ARVO (1962-2015); The Authors (2016-present)
People with normal vision perform activities of daily living binocularly, while changing the viewing distance frequently and effortlessly. Patients with AMD use preferred retinal loci (PRLs) from the functional eccentric retina to perform visual tasks, but their ocular motor control is impaired and this can affect visual performance. In this study we examined how viewing distance affects fixation stability during binocular viewing.
Ten patients with bilateral AMD participated. Visual acuity at 6m was recorded with the ETDRS acuity test and monocular PRL location was recorded with the MP-1 microperimeter. Each patient’s better eye (BE) and worse eye (WE) were identified based on their visual acuity. Fixation stability during binocular viewing was recorded simultaneously for the two eyes with an eye-tracker at 3 viewing distances (40cm, 1m, 6m) in random order. At each viewing distance, patients were asked to look at a 3deg cross and their eye-movements were recorded at 120 Hz for 15s. Fixation stability was evaluated with a bivariate contour ellipse area.
Mean binocular visual acuity was .42 ± .18 logMAR, that of the BE was .42 ± .14 logMAR, and that of the WE was .83 ± .23 logMAR. Fixation stability during binocular viewing was analyzed with a 3 (distance: 40cm, 1m, 6m) x 2 (eye: BE, WE) repeated measures ANOVA. There was no effect of viewing distance on fixation stability (p =.72). Fixation stability of BE and WE were not different from each other (p=.80). There was no interaction effect (p = .93).
Viewing distance does not affect fixation stability during binocular viewing in patients with AMD. Fixation stability data recorded during binocular viewing with an instrument with a fixed viewing distance can be used in conjunction with visual tasks performed at other viewing distances.
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