ABSTRACT Purpose The balance of responses between the ON and OFF pathways is believed to play an important role in myopia. This pilot study compared the difference in visual acuity under two contrast polarities between myopic children (corrected and uncorrected) and emmetropic children. Methods Two groups of children aged 8–12 years were enrolled: a myopic group (spherical equivalent SEQ between −0.75 D and −6.00 D, N = 11) and a normal control group ( N = 16). Visual acuities were measured using an Early Treatment Diabetic Retinopathy Study program, which presented either white letters against a black background or black letters against a white background. Visual acuity (corrected and uncorrected for the myopic group) under both polarities was tested in randomized order and repeated after a 30‐min interval. Visual acuities were reported as letter scores. The ON/OFF ratios of visual acuity scores under the two polarity conditions were calculated and correlated with SEQ. Results When uncorrected, white‐letter visual acuity was significantly better than black‐letter visual acuity ( p < 0.001) for the myopic group, with a difference of 6 letters (equivalent to 0.12 logMAR). No significant differences in visual acuity scores between the two polarities were found when the myopic group was corrected or in the control group. This suggests that uncorrected myopic eyes have greater difficulty in resolving the spatial resolution of black letters as compared to white letters. The ON/OFF ratio in the uncorrected myopic group was significantly higher than in the corrected myopic group and the control group (1.14 ± 0.09 vs. 0.99 ± 0.04, 1.00 ± 0.03, p < 0.001). When uncorrected, the ON/OFF ratio correlated with SEQ ( R = 0.38, t = −2.4, p = 0.02), indicating that the ON/OFF imbalance increases with the magnitude of uncorrected myopic blur. Conclusions Children with uncorrected myopic eyes had more difficulty in recognizing black letters compared to white letters, and the ON/OFF imbalance was correlated with the magnitude of uncorrected myopic blur.
Chen et al. (Sun,) studied this question.