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Irene Tran, Mitchell W. Dul, William H. Swanson; Normal Variability For Two Forms Of Perimetry Using Anatomically Inspired Test Locations. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4810.
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© ARVO (1962-2015); The Authors (2016-present)
To assess normal perimetric variability at test locations inspired by optic nerve and nerve fiber layer maps, using size III perimetry and Contrast Sensitivity Perimetry (CSP).
34 eyes of 34 young control subjects were tested with both forms of perimetry, totaling 4 visual fields with size III perimetry, and 4 visual fields with CSP. Subjects were tested twice on each form of perimetry on two separate days. Sensitivity was measured at 56 locations in the central visual field, based on maps for neuro-retinal rim (Asaoka et al., 2009, ARVO E-Abstract #4400) and retinal nerve fibers (Jansonius et al., Vision Res. 2009, 49:2157-2163), using HFA II Model 750i with Goldmann size III stimuli and Contrast Sensitivity Perimetry (CSP) with Gabor sine stimuli. Gabor sines had peak spatial frequencies ranging from 0.14-0.50 cycle/deg, were scaled for location, and flickered at 5 Hz. Between-subject and test-retest variability were computed for each stimulus and each test location using the standard deviation (SD) expressed in dB, where 1 dB = 0.1 log unit. Variability as a function of eccentricity was computed using 2 sets of 16 test locations: within 10° of fixation and 20-27° from fixation.
Between-subject variability was similar for CSP and size III within 10° of fixation, averaging 1.3 ± 0.3 dB for CSP and 1.4± 0.3 dB for size III (t = 1.59, p > 0.3). SD increased at 20-27° for size III (t=4.6, p < 0.0005) but not for CSP (t=1.13, p > 0.26). Between-subject variability across all locations was more strongly correlated with eccentricity for size III (r2 = 2%, p < 0.0001) than for CSP (r2 = 0.1%, p < 0.01), and the difference in slopes was significant (z = 25.3. p < 0.0001). Test-retest variability was on average higher for size III than CSP (t = 6.8, p < 0.0001), and increased more dramatically with eccentricity (z = 7.0, p < 0.0001). Contrast sensitivity declined with eccentricity at -0.20 dB per degree for the size III stimulus (r2 = 38%) and -0.01 dB per degree for the CSP stimuli (r2 = 1%).
Normal variability was lower for CSP compared to size III, consistent with weaker effects of eccentricity for CSP.
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