Abstract
Abstract: :
Purpose: Up to 50% of children with congenital nystagmus (CN) will adopt an anomalous head position (AHP) in an attempt to improve vision by repositioning their eccentric gaze "null" zone to primary position. It has not been clear from previous studies what benefit the AHP provides to the CN patient in terms of visual acuity (VA). The purpose of this study is to deterimine whether patients with congenital nystagmus and an AHP have better binocular VA than those patients without an AHP. Methods: This study was a prospective case series of clinically and oculographically diagnosed patients with CN (n=125). Primary analysis compared binocular visual acuity in patients with and without an AHP. The relationships between binocular visual acuity, visual sensory system disease, and the presence of an AHP were also studied. VA was measured using the Amblyopia Treatment Study Visual Acuity Testing HOTV optotype protocol or ETDRS chart. Excluded from the study were patients who were unable to provide reliable visual acuity data or who demonstrated mixed congenital/ latent nystagmus. Results: Sixty-four patients met entry criteria for the study. Thirty-eight patients (59.4%) had an AHP while 26 (40.6%) did not (p=0.031). Patients with and without an AHP were not statistically different in age, sex, or incidence of strabismus. Mean VA was 20/42 (logMAR 0.52) in patients with an AHP and 20/83 (logMAR 0.62) in patients without AHP (p<0.001). Seventeen of 38 patients with AHP (44.7%) and 20 of 26 patients without AHP (76.9%) showed some evidence of sensory system disease (p=0.005). Among patients with sensory system disease, those with an AHP had a mean VA of 20/55 (logMAR 0.44) and those without an AHP had a mean VA of 20/108 (logMAR 0.73), p<0.001. Conclusions: VA was found to be significantly better in CN patients with an AHP. Our new findings indicate that the presence of an AHP in a patient with congenital nystagmus correlates with good vision, and thus may be considered a positive prognostic sign in a pre-verbal child.
Keywords: nystagmus • visual acuity • eye movements: recording techniques