Slow reading in children with anisometropic amblyopia is associated with fixation instability and increased saccades

Abstract

Background: Previous studies show slow reading in strabismic amblyopia. We recently identified amblyopia, not strabismus, as the key factor in slow reading in children. No studies have focused on reading in amblyopic children without strabismus. We examined reading in anisometropic children and evaluated whether slow reading was associated with ocular motor dysfunction in children with amblyopia.

Methods: Anisometropic children (7-12 years) with or without amblyopia were compared to age-similar normal controls. Children silently read a grade-appropriate paragraph during binocular viewing. Reading rate (words/min), number of forward and regressive saccades (per 100 words) and fixation duration were recorded with the ReadAlyzer. Binocular fixation instability was also evaluated (EyeLink 1000).

Results: Amblyopic anisometropic children read more slowly (n = 25; mean with standard deviation, 149 ± 42 words/min) than nonamblyopic anisometropic children (n = 15; 196 ± 80 words/min; P = 0.024) and controls (n = 25; 191 ± 65 words/min; P = 0.020). Nonamblyopic anisometropic children read at a comparable rate to controls (P = 0.81). Slow reading in amblyopic anisometropic children was correlated with increased forward saccades (r = -0.84, P < 0.001), increased regressive saccades (r = -0.85, P < 0.001), and fellow eye instability during binocular viewing (r = -0.52, P = 0.019).

Conclusions: Slow reading in school-age children with anisometropic amblyopia is related to increased frequency of saccades and fixation instability of the fellow eye. Further research should consider the effects of slower reading on academic performance.

FIG 1

Bar graphs depicting group means for reading rate, number of forward saccades, number of regressive saccades, and fixation duration for amblyopic anisometropic children (light gray bars), nonamblyopic anisometropic children (white bars), and normal control children (dark gray bars). Amblyopic anisometropic children were significantly slower at reading and produced more forward saccades compared with nonamblyopic anisometropic children and normal control children. No significant group differences were found for number of regressive saccades or fixation duration. Error bars represent ± standard error of the mean. * P < 0.05; ** P < 0.01.

FIG 2

Scatterplots depicting significant correlations between reading rate and ocular motor outcomes measured with the Readalyzer during binocular reading (no. forward saccades, no. of regressive saccades), fellow eye fixation instability during binocular viewing and amblyopic eye best-corrected visual acuity for amblyopic anisometropic children.