Accommodation, pattern glare, and coloured overlays.

We manipulated the accommodative response using positive and negative lenses to study any association between symptoms of pattern glare and accommodation. Two groups of eighteen young adults were selected from seventy-eight on the basis (i) that their rate of reading increased by 5% or more with an overlay compared to their rate without it, and (ii) that they reported more than 2 symptoms of pattern glare (group 1) or had no such increment in reading speed and reported fewer than 3 symptoms (group 2). Under double-masked conditions participants observed at 0.4 m a pattern of stripes while measurements of accommodation were made using an open field autorefractor with and without positive and negative trial lenses (0.75 D), and with and without a coloured overlay. Pattern glare was also assessed with and without the trial lenses. Without lenses, the mean accommodative response in group 1 was 1.55 D, a lag of 0.95 D +/- 0.24 D relative to the demand. The lag decreased by 0.43 D (p < 0.0001) when the chosen overlay was used, an effect that was not shown in group 2 even when lag increased with negative trial lenses (p = 0.13). In both groups, pattern glare scores were reduced by the trial lenses, but were unaffected by the sign of the lenses. This suggests that symptoms of pattern glare are not strongly associated with accommodative response.