Comparison of two methods for measuring contrast sensitivity in anisometropic amblyopia

This study aimed to evaluate two psychophysical contrast sensitivity testing methods in amblyopic patients. Thirty-three adults with anisometropic amblyopia participated in this study. Psychophysical contrast sensitivity was measured for both amblyopic and fellow eyes of the participants at 1, 3, and 5 cycles per degree (cpd) spatial frequencies by Freiburg visual acuity and contrast test (FrACT) and Metrovision contrast sensitivity test, which employ sine-wave gratings for measurement of contrast sensitivity. We evaluated the correlation between the two tests and used Bland–Altman analysis to measure the agreement between the two methods. Except for 1 cpd in amblyopic eyes, FrACT showed significantly higher contrast sensitivity measurements than Metrovision at all spatial frequencies both in normal and amblyopic eyes (P < 0.01). The difference between the two methods increased with an increase in spatial frequency. There was a significant correlation between the two tests at most of the spatial frequencies. While the difference between the results of the two tests increased with an increase in contrast sensitivity in amblyopic eyes, we found an inter-test agreement in normal eyes. Although both FrACT and Metrovision employ sine-wave gratings to measure contrast sensitivity, there are some differences between them, and their results can not be used interchangeably.