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Kristi Kester, Tawna L Roberts, Richard W Hertle; Repeatability of Visual Acuity Measured in Eccentric Gaze in Patients with Infantile Nystagmus Syndrome. Invest. Ophthalmol. Vis. Sci. 2017;58(8):757. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Infantile nystagmus syndrome (INS) is a specific ocular motor disorder with characteristic clinical findings and electrophysiology. Patients with INS often have a null-zone (eye in orbit, or gaze position) where the nystagmus intensity is at its minimum. This physiological null zone often results in an anomalous head posture by the patient to achieve better visual function. Optotype visual acuity (OVA) as a measure may not reflect the deficit imposed on the visual system as a result of the nystagmus. A better measure may be OVA as a function of gaze. The purpose of this study was to assess the test-retest reliability of OVA across horizontal gaze in patients with INS and adult controls to determine if gaze dependent OVA (GDOVA) is a reliable methodology.
Test and re-test OVA were measured binocularly using the ETDRS protocol on the Electronic Visual Acuity (EVA) testing system. Subjects (n=34; 20 INS ages 8-47 years, and 14 control ages 21-65 years) were seated 3 M from a monitor and OVA measured in 7 horizontal gaze positions from 30 degrees left to 30 degrees right in 10 degree steps with the order randomized. OVA testing was repeated twice in each of the 7 gaze positions. Head position was monitored using a cervical range of motion headpiece (CROMR). The letter score obtained by the EVA system was converted to logMAR. Test-retest reliability was assessed using intraclass correlation coefficients (ICC) and two-factor repeated measures (gaze position and group) analysis of variance (ANOVA).
Test-retest reliability was high in both the INS and control subjects as the difference in test-retest OVA for both the experimental and control groups was on average less than 0.1 logMAR in each of the 7 gaze positions. The ICC was ≥0.98 in the INS group and ≥0.88 for the control group in each of the 7 gaze positions. A significant difference in letter score was not detected using a two-factor repeated measures ANOVA between group (p=0.053), gaze (p=0.266), or interaction of group and gaze (p=0.789).
OVA testing has excellent repeatability across 60 degrees of horizontal gaze in patients with INS and normal adult controls. GDOVA is a reliable measure and may be a valuable tool as an outcome variable in studies involving patients with INS.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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