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Andrea N. Fry, Alyssa M. Gehring, Molly K Lalonde, Richard W Hertle, Tawna L Roberts; Repeatability of Low-Contrast Visual Acuity Across Horizontal Gaze in Patients with Infantile Nystagmus Syndrome. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1082.
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© ARVO (1962-2015); The Authors (2016-present)
Infantile Nystagmus Syndrome (INS) is a specific ocular motor disorder consisting of an early onset, involuntary oscillation of the eyes. Patients with INS have a position of the eye in orbit where the nystagmus intensity is least, a “null-zone.” The null zone in an eccentric orbital position which often results in an anomalous head posture to achieve improved visual function. We have shown that gaze dependent high-contrast visual acuity has excellent test-retest reliability in patients with INS. The purpose of this study was to assess the test-retest reliability of low-contrast visual acuity (LCVA) across horizontal gaze in patients with INS to determine if gaze dependent LCVA is a reliable a testing methodology.
Test and re-test LCVA was measured binocularly using the ETDRS protocol on the Electronic Visual Acuity (EVA) tester, using low-contrast (5%) letters at 3M in 18 INS subjects (9-47 years) and 20 control subjects (19-53 years) in 7 horizontal gaze positions from 30 degrees (deg) left to 30 deg right in 10 deg steps with the order randomized. Test-retest LCVA was performed in each gaze position. Head position was monitored using a cervical range of motion headpiece. LCVA letter score was converted to logMAR. Test-retest reliability was assessed using intraclass correlation coefficients (ICC) and repeated measures two-factor (gaze position and group) analysis of variance (ANOVA) with Holm-Sidek posthoc analysis.
The mean difference in test-retest LCVA for each gaze position was ≤0.14 logMAR for INS subjects (0.10±0.03, 0.6-0.14) and 0.05 in control subjects (0.05±0.01, 0.03-0.06). There was a significant difference between group (p<0.001) but not gaze position (p=0.95). A significant interaction between group and gaze was found (p=0.002). Post-hoc analysis showed differences between groups in 10 deg right gaze and 30 deg left gaze. Test-retest reliability was high in both INS (ICC≥0.77) and control subjects (ICC≥0.83).
LCVA has excellent reliability in both INS and control subjects across 60 deg of horizontal gaze with the average difference of test-retest being one line in INS subjects and 0.5 line in control subjects. There were no systematic differences in LCVA between groups and the differences detected are unlikely to be clinically meaningful. LCVA is a reliable measure for visual function patients with INS.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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