Abstract
Purpose:
It’s now clear that intensive monocular perceptual learning can improve visual acuity, contrast sensitivity, and vernier acuity in the amblyopic eye of adults with amblyopia. It is however not clear how much monocular training can enhance binocular vision. In the current study, we aimed to determine the effects of monocular training on a variety of binocular visual functions.
Methods:
Eleven adults with anisometropic amblyopia (22±1.4 yrs) were trained in a grating contrast detection task near each individual’s cutoff spatial frequency for 8 to 10 days, with 630 trials/day. Visual acuity, stereo acuity, monocular and binocular contrast sensitivity functions (CSF) with the quick CSF method (Lesmes, et al., 2010), perceived phase of binocularly combined sinewave gratings as a function of interocular image contrast ratio (Huang et al., 2009), pAE dominance in viewing dichoptically presented incompatible images of equal contrasts were measured before and after training.<br />
Results:
Training substantially improved contrast sensitivity at the trained spatial frequency (by 75.4%), area under the CSF (by 94%), and visual acuity (logMAR from 0.62 to 0.42 or 2 lines) in the amblyopic eye. It also significantly improved stereo acuity (from 1530.9” to 110.7”) and increased the dominance duration of the amblyopic eye (from 2% to 13% in binocular rivalry). The improved dominance of the amblyopic eye was through elongation of each dominant phase without alteration of the switching frequency between the two eyes. On the other hand, training didn’t significantly improve the ratio of the areas under binocular and monocular fellow eye CSFs (from 1.1 to 1.08, p>0.1) and the interocular contrast ratio at which the two eyes contribute equally to binocular phase combination (from 0.11 to 0.13, p>0.10). There is no significant correlation between improvements in visual acuity, stereo acuity, and binocular rivalry.<br />
Conclusions:
Although monocular training can improve visual acuity and contrast sensitivity and eye dominance of the amblyopic eye, the magnitudes of improvements didn’t correlate with each other; the impact on binocular summation and binocular phase combination was not significant. The results strongly suggest that structured monocular and binocular training is necessary to fully recover deficient visual functions in amblyopia.<br />