|Title||Bailey-Lovie and Grating acuity in subjects with and without Down syndrome|
|Author, Co-Author||Kelsie Morrison, Ayeswarya Ravikumar, David Berntsen, Heather Anderson|
Purpose: Down syndrome (DS) is associated with reduced acuity attributable to both optical and cognitive factors. This study compares measures of grating (resolution) acuity and Bailey-Lovie (recognition) acuity (BL) in subjects with and without DS.
Methods: Monocular logMAR BL and grating acuity (4 alternative forced choice paradigm) was recorded for one eye in 16 subjects with DS (mean age: 26 ± 9 years; range: 18 to 46) and 24 controls (mean age: 30 ± 9 years; range: 19 to 48). BL acuity was tested on a computer controlled, linearized display. Subjects read lines of decreasing size until 5 letters were missed. Testing was repeated with 3 separate charts and an average threshold determined. For the grating acuity, 8 trials at each acuity size were presented until subjects reached the guess rate (2 of 8 correct). Grating acuity was defined as the 62.5% threshold on a fitted psychometric function. Repeated-measures ANOVA with Tukey HSD post-hoc t-tests were used to compare acuity thresholds across groups and tests.
Results: Average acuity for controls was -0.04 ± 0.08 (BL) and -0.11 ± 0.06 (grating). Acuity for subjects with DS was 0.45 ± 0.16 (BL) and 0.57 ± 0.26 (grating). Differences between acuity test type depended upon the subject group (type x group interaction, p < 0.001). Acuity thresholds were significantly different between groups for both acuity tests (both p < 0.05; Tukey). Acuity thresholds were also significantly different between acuity tests within each group (both p < 0.05; Tukey). While controls improved an average of 3 letters with grating acuity vs BL, subjects with DS performed an average of 6 letters worse on grating acuity vs BL.
Conclusions: Acuity was worse in subjects with DS compared to controls irrespective of acuity test. While controls performed better on the resolution grating task, subjects with DS performed worse, likely due to difficulties with reliable identification of the right/left directionality required of the task.
Acknowledgments: NIH EY024590
|Affiliation of Co-Authors||University of Houston College of Optometry, University of Houston College of Optometry, University of Houston College of Optometry|