Comparison of SLO Perimetry, Binocular Perimetry, and Functional Visual Field Perimetry in Patients with Macular Scotomas

Abstract

Abstract: : Purpose: To determine if: 1) monocular projection perimetry with fixation control is as accurate as SLO perimetry; 2) monocular visual fields accurately predict binocular visual fields; and 3) binocular visual fields accurately predict functional visual fields. Methods: 14 patients were evaluated with: 1) Moncular and binocular projection perimetry (with fixation controlled by pupil eye tracker); 2) SLO macular perimetry (monocularly); and 3) Functional Visual Field (FVF) perimetry. Perimetry stimuli were matched for all tests (20 minarc size and retinal illuminance matching the 1400 cd/m2 luminance of the projector). FVF testing requires finding the stimlus location in 24 locations of the central visual field (radial pattern, 45 degree spacing with 3 testing points on each radial arm; mean response time and accuracy are recorded for each location). FVF were obtained from 20 normally sighted subjects as a control. SLO monocular visual fields were combined by computer modeling to predict the binocular visual fields. Results: Subjects were from 58 to 83 years old (median 68); had visual acuity from 20/120 - 20/500 (median 20/200); and had macular scotoma areas of 28 to 210 degrees squared (median 63). The macular scotoma areas and locations determined by projection perimetry were not significantly different (matched pair t-test) compared to SLO macular perimetry. SLO monocular visual fields when combined to predict binocular visual fields (volume scotoma) are significantly different than the binocular visual fields found by projection perimetry. Subjects with macular scotomas had FVF response times from 0.6 to 9.5 seconds (median 3.6) while normal subjects had response times from 0.5 to 1.8 seconds (median 0.7). The normal subjects 95% quantile response time of 1.1 seconds was used as the criteria for normal or abnormal response times for FVF. FVF areas were significantly larger than the binocular visual fields while location accuracy for macular scotoma subjects and normal subjects were the same. Conclusions: Macular scotomas affect everyday function. While monitoring eye movements during perimetry provides an effective means of measuring macular scotomas (for retinal disease treatment, for example), the important parameters of macular scotomas for rehabilitation are the binocular macular scotoma characteristics including the ability of "seeing around" the scotoma. This study demonstrates an effective means of measuring binocular visual fields and the impact of these binocular macular scotomas on everyday function (Functional Visual Fields).

Keywords: low vision • perimetry • visual fields