The impact of using reverse polarity text for children with vision impairment assessed using light-adapted flicker...

Children with vision impairment can have difficulty accessing classroom reading material and knowledge of which students are likely to have improved performance reading performance with reverse polarity would be of value to educators.

Printed material is typically presented as black text on a white background; however, reversing the polarity to white text on a black background may improve the reading speed for children with vision impairment. This study sought to identify the visual function or pathological features of children with vision impairment where reversing the polarity of text would improve their reading performance.

Forty-eight vision-impaired participants (27 male), aged 5-18 years with binocular visual acuities between 0.18-1.52 logMAR, were included. Reading performance was assessed by changes in Critical Print Size (ΔCPS), Maximum Reading Speed (ΔMRS) in normal and reverse polarity digital print, and numeric reading speed (ΔNRS) with normal and reverse polarity fonts. Correlations were made with 30 Hz flicker electroretinogram amplitude and high/low contrast acuity. Paired nonparametric tests evaluated significance in pathological condition groups.

Significant negative correlations were only found between the 30 Hz flicker amplitude and ΔMRS (r = -.42, p = .028) and ΔNRS (r = -.46, p = .027). Follow-up pairwise comparisons based on pathology group only showed a significant effect of the retinal dystrophy group and CPS (n = 12, z = -2.24, p = .025). All other pairwise comparisons based on group were non-significant (p > .05).

This study did not identify a specific pathological group or visual functional measure that could be used as a clinical marker to predict the impact of reversing polarity. However, significant improvements could be made in reading performance for some children and so a reading performance assessment is recommended for all children with vision impairment.