Comparison of Wavefront-optimised Refraction Determined Pre- and Post-cycloplegia in Individuals with Down Syndrome

To compare metric-optimised refractions determined from wavefront aberration measures with the COAS-HD wavefront aberrometer pre- and post-dilation and the resultant visual acuity through each refraction in participants with Down syndrome (DS).

Twenty-one adults (mean age = 31 ± 9 years) and 21 children (mean age = 11 ± 4 years) with DS had wavefront aberrations measured pre- and post-dilation. A mathematical programme applied a large range of sphero-cylindrical refractions to the uncorrected wavefront error for each eye and calculated the resultant visual Strehl ratio (VSX). The refraction providing the single best value of VSX was identified from both the pre- and post-dilation analyses. Participants returned for a second visit for in-office tests of visual acuity while viewing through pre- and post-dilation-optimised refractions. For analysis, refractions were converted to M, J₀ and J₄₅ vectors and the total dioptric difference between pre- and post-dilation refractions calculated. Visual acuity pre- and post-dilation was compared using the Wilcoxon signed-rank test.

The estimated median total dioptric difference (Q1, Q3) between pre- and post-dilation refractions was 0.66 D (0.47, 1.11) in the right and 0.80 D (0.44, 1.12) in the left eyes of children and 0.90 D (0.41, 1.43) and 0.74 D (0.42, 1.32) in the right and left eyes of adults. The M-value was significantly more hyperopic in both children and adults post-dilation (p = 0.001). There was no significant difference in the monocular or binocular distance visual acuity between the pre- and post-dilation acuity measures in adults and children (p > 0.14).

Dilation status significantly affected the metric-optimised refractive outcomes but did not affect visual acuity significantly in adults and children with DS. While the median difference between pre- and post-dilation measures was around 0.66-0.90 D, some individual differences reached multiple dioptres, suggesting that dilation upon an initial visit is still important for a subset of individuals.