Slow Binocular Reading in Amblyopic Children is a Fellow Eye Deficit

Significance Amblyopic children read 25% slower than their peers during binocular silent reading. Purpose We compared binocular reading to fellow eye reading to determine whether slow reading in amblyopic children is due to binocular inhibition i.e., the amblyopic eye is interfering during binocular reading. Methods In a cross-sectional study, 38 children with amblyopia and 36 age-similar control children who completed grades one to six were enrolled. Children silently read grade-appropriate paragraphs during binocular reading and fellow eye reading while wearing ReadAlyzer eye-tracking goggles. Reading rate, number of forward saccades, number of regressive saccades, and fixation duration were analyzed between groups and between viewing conditions. We also examined whether sensory factors (amblyopia severity, stereoacuity, suppression) were related to slow reading. Results For amblyopic children, binocular reading versus fellow eye reading did not differ for reading rate (176 ± 60 wpm vs 173 ± 53 wpm, p = .69), number of forward saccades (104 ± 35 saccades/100 words vs 97 ± 33 saccades/100 words, p = .18), number of regressive saccades (21 ± 15 saccades/100 words vs 22 ± 13 saccades/100 words, p = .75), or fixation duration (0.31 ± 0.06 sec vs 0.32 ± 0.07 sec, p = .44). As expected, amblyopic children had a slower reading rate and more forward saccades than control children during binocular reading and fellow eye reading. Slow reading was not related to any sensory factors. Conclusions Binocular reading did not differ from fellow eye reading in amblyopic children. Thus, binocular inhibition is unlikely to play a role in slow binocular reading, and is instead a fellow eye deficit that emerges from a disruption in binocular visual experience during development.