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N. V. Odell, D. A. Leske, S. R. Hatt, W. E. Adams, J. M. Holmes; The Effect of Induced Monocular Acuity Deficits on Stereoacuity. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2587.
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To determine the effect of induced monocular visual acuity deficits on stereoacuity measured using ‘real depth’ and ‘random dot’ tests.
Monocular visual acuity deficits (range 20/15 to 20/1600) were induced sequentially with 7 different Bangerter filters (<0.1, 0.1, 0.2, 0.3, 0.4, 0.8, and 1.0) in 15 normal adult subjects. Visual acuity and stereoacuity were assessed at each filter density and with no filter. Stereoacuity was measured with the Frisby and Frisby Davis Distance (FD2) (real depth tests) and Near Preschool Randot (PSR) and Distance Randot (DR) (random dot tests). Testing was repeated with each filter over the fellow eye, creating a total of 240 trials for each stereotest. To account for potential bias of comparing tests with different measurable minimum and maximum levels, stereoacuity results were grouped as "fine" (20-60 arcsec), "moderate" (>60-200 arcsec) or "coarse/nil" (>200-nil) stereo. The frequency of "fine", "moderate", or "coarse/nil" responses was determined for each LogMAR acuity level, for each stereoacuity test.
Measured stereoacuity was more severely degraded with random dot tests (DR, PSR) compared with real depth (FD2, Frisby) tests (Medians: DR=coarse/nil (800 arcsec); PSR=moderate (100 arcsec), FD2=fine (60 arcsec) and Frisby=fine (40 arcsec), P<0.0001 for each comparison). The worst monocular visual acuity associated with fine stereoacuity in all subjects was 20/50 for Frisby, 20/20 for FD2, better than 20/15 for PSR, and better than 20/15 for DR. The worst monocular visual acuity associated with at least moderate (fine or moderate) stereoacuity in all subjects was 20/80 for Frisby, 20/63 for FD2, 20/25 for PSR, and better than 20/15 for DR. Course/nil stereoacuity was always associated with worse than 20/320 for Frisby, 20/1600 for FD2, 20/125 for PSR and 20/63 for DR.
We have defined levels of monocular visual acuity degradation associated with fine, moderate, or nil stereoacuity. Measured stereoacuity using real depth tests (Frisby and FD2) is less easily degraded by reduced monocular visual acuity than using random dot tests (PSR and DR). These findings have important implications for testing stereoacuity in clinical populations.
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