Abstract
Purpose: :
To determine the relationship between visual function and functional vision in everyday tasks over repeated testing for two years in people with restricted visual fields due to RP.
Methods: :
Visual functions (ETDRS acuity, SKILL chart near acuity and dark acuity, CRT presented Grating acuity, Dynamic Visual Acuity, Pelli-Robson contrast sensitivity, Humphrey Visual Fields, SLO Macular Perimetry, flicker sensitivity, and motion sensitivity) were tested binocularly in 30 people with visual fields 20 degrees or less due to RP (retinitis pigmentosa). Functional vision (MNRead reading performance, Pepper Test reading performance, Dynamic Visual Fields, Face Recognition, Visual Search of normal scenes and artificial scenes (where's Waldo type), and mobility in a controlled lab environment) was tested binocularly in the same people. Self-report outcome measures included the VA-28, mobility assessment, and falls history.
Results: :
Subjects had median visual acuity of 0.42 logMAR (range: 0.00 to 1.68) and median contrast sensitivity of 1.00 logcontrast (range: 0.00 to 1.75). All subjects had some visual function deficits in the central 20 degrees as well as restricted visual fields. Median near/dark acuity was 0.42/2.00 logMAR. Median MNRead/Pepper average maximum reading rate was 180.0/81.4 (range: 0/0 to 342/109) words per minute. Median correct face recognition was 79 (range: 0 to 96) out of 96 faces. Median modified dynamic gait index was 19 (range: 9 to 24). Median normalized dynamic visual acuity was 0.16 (range: 0.09 to 0.37). Dynamic visual field times were from 0.60 to 8.2 seconds (95% of normally sighted subjects have times of 1.0 second or less). Subject's self-reported ratings of abilities, independence and satisfaction of the 28 everyday functional tasks were not significantly related (contingency table analysis). Regression analysis (linear and Ordinal logistic) found that the functional vision and self-report outcome measures were more strongly related (if significantly related; p > 0.05) to dynamic visual acuity and dynamic visual field times than to other visual function measures like visual acuity, contrast sensitivity, or visual field loss. Further analysis of the relationships between visual function and functional vision in everyday tasks will be presented. Repeated measures for 10 subjects that had at least four testing sessions over two years will also be presented.
Conclusions: :
Measures of Dynamic Visual Function may be better outcome measures of the effect of vision loss on everyday function than standard visual function measures.
Keywords: low vision • shape, form, contour, object perception • retinitis