The effect of transient glare on shape discrimination threshold in myopic adults

Background: The aim was to evaluate the effect of transient glare on shape discrimination threshold (SDT) in myopic adults. Methods: A total of 162 myopic subjects were enrolled. Of these, 121 had low to mid myopia (−1.00 D to −6.00 D) and 41 had high myopia (−6.13 D to −10.25 D). All subjects had corrected visual acuity of 6/6 or better, and only data for the right eye were included in the study. SDTs were measured with circular D4 (fourth derivative of Gaussian) radial frequency patterns with a radial frequency of four, peak spatial frequency of three cpds, and mean radius of 1.5 degrees. SDTs were measured under two conditions, with and without the presence of transient glare while the stimulus was displayed (duration = 500 ms). Results: Without transient glare, SDTs were not different between the low-mid (23.84 ± 6.02 arcsec) and high myopia groups (25.17 ± 5.98 arcsec, p = 0.16, Mann–Whitney test). With transient glare, SDTs in all subjects became significantly higher (p < 0.001, Wilcoxon signed-rank test). SDTs in the high myopia group (55.53 ± 18.59 arcsec) became significantly higher than those in the low to mid myopia group (47.55 ± 15.06 arcsec, p = 0.014, Mann–Whitney test). The increments were significantly higher in the high myopia group (28.94 arcsec versus 20.88 arcsec, p = 0.031, Mann–Whitney test). Multiple regression showed that SDTs with glare were significantly associated with SDTs without glare (p < 0.001) and the presence of high myopia (p = 0.015). Conclusions: Transient glare significantly increased SDTs in all myopic subjects, with the increment in subjects with high myopia being significantly larger than those in subjects with low to mid myopia.