Abstract
Purpose :
Amblyopic children read 25% slower than controls during binocular silent paragraph reading, with slower reading being strongly correlated with an increased number of forward saccades (Kelly et al, J AAPOS 2015, 2017). Slower reading in adults with central scotomas is also accompanied by increased forward saccades, associated with decreased perceptual span, fixation instability, and eccentric viewing. Here, we investigate whether reduced perceptual span, fixation instability, and eccentric fixation are associated with increased forward saccades during reading by amblyopic children.
Methods :
Amblyopic children aged 7-12 years who completed 1st – 5th grade were enrolled (n=121; amblyopic eye VA: 0.2-1.1 logMAR). Wearing the ReadAlyzer eye movement recording system, children silently read a grade-level paragraph binocularly. Reading rate, number of forward and regressive saccades per 100 words, and fixation duration were determined. Perceptual span size was estimated by measuring the character length of each forward saccade. Fixation instability was evaluated (EyeLink 1000) as the child binocularly fixated a small dot for 20 secs, and was summarized as log BCEA for each eye and for vergence. Eccentric fixation was measured using spectral domain OCT and was defined as the horizontal distance between the fovea and fixation point, adjusted for axial length and converted into visual degrees.
Results :
The strong correlation between slow reading and increased forward saccades was confirmed (r=-0.70; CI95%: -0.78,-0.60). The increase in forward saccades was strongly associated with reduced perceptual span (r=-0.72; CI95%: -0.79,-0.62) and eccentric fixation (r=0.50 CI95%: 0.19,0.72). Eccentric fixation was correlated with slow reading (r=-0.64; CI95%: -0.85, -0.26), increased forward saccades (r=0.50 CI95%: 0.06,0.78), and increased vergence instability (r=0.46 CI95%: 0.12 to 0.76). No significant correlations were observed with fixation duration or regressive saccades.
Conclusions :
The increase in forward saccades that characterize slow reading in amblyopia is associated with reduced perceptual span. Perceptual span provides information about word boundaries and word length to guide saccade planning. Perceptual span can be enhanced with ocular motor training or perceptual learning (Pijnacker et al 2011), which may be useful in rehabilitation of amblyopic children who read slowly.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.