Visual Acuity in Eccentric Gaze in Patients with Infantile Nystagmus Syndrome (INS)
Rachida Bouhenni; Tawna Roberts; Andrea Fry; Kristi Kester; Richard Hertle
Akron Children’s Hospital
Introduction: Patients with INS often have a null-zone where the nystagmus intensity is at its minimum, resulting in an anomalous head posture to achieve better visual function (VF). Traditional measures of VF in primary gaze may not reflect the deficit imposed on the visual system, thus an improved method would be to measure vision as a function of gaze position. The purpose of this study was to assess the test/re-test of high-contrast (HCVA) and low-contrast (LCVA) visual acuity across horizontal gaze (HG) to determine if gaze dependent visual acuity (GDVA) measures are reliable.
Methods: Separate studies of subjects with HCVA (INS: n=20; 8-47 years; Control: n=14; 21-65 years) and LCVA (INS: n=18; 9-47 years, Controls: n=20; 19-53 years) were completed. Testing was performed binocularly in HG (30º left to 30º right in 10º steps) twice in each position. Test-retest reliability was analyzed using intraclass correlation coefficients (ICC). Differences between groups and gazes were determined by ANOVA.
Results: ICC was high for HCVA (INS: >/=0.97; Control: >/=0.88) and LCVA (INS: >/=0.77; Control: >/=0.83) for each gaze. A significant difference in letter score was not detected between group, gaze, or interaction of group and gaze for HCVA (p>0.05). For LCVA, a significant difference in test-retest was detected between groups (INS>Control; p<0.05) and interaction between group and gaze (p<0.05).
Discussion: Despite INS patients having significantly larger differences in test/retest than controls, using LCVA, on average, both HCVA and LCVA testing has excellent repeatability across 60° of HG.
Conclusion: GDVA is a reliable measure of VF in INS patients.
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