PURPOSE: Dichoptic training is becoming a popular tool in amblyopia treatment. Here we investigated the effects of dichoptic training on juvenile amblyopia no longer responsive to patching treatment (PT group) or never patch treated (NPT group).
METHODS & RESULTS: Training consisted of three stages. (1) 10 PT and 10 NPT amblyopes (8-17 years, 11-anisometropic, 4-ametropic, 1-strabismus, 4-mixed) received dichoptic de-masking training for 40 hours. They used AEs to practice contrast discrimination of Gabors that were dichoptically masked by a band-filtered noise pattern simultaneously presented in NAEs. Dichoptic learning is indexed by the increase of maximal tolerable noise contrast (TNC) for AE contrast discrimination. Training improved maximal TNC by 600% in PT and 700% in NPT, which translated to stereoacuity improvements by 5.4-lines in PT and 3.6-lines in NPT, and AE visual acuity improvements by 1.1-lines in PT and 2.2-lines in NPT. (2) The amblyopes further received stereopsis training for another 40 hours. Training improved stereoacuity by 3.3-lines in PT and 0.3-lines in NPT, and AE acuity by 0 line in PT and 0.4 lines in NPT. Seven PT amblyopes regained normal stereoacuity (20~50 arcsec) after two stages of training. (3) Extra monocular AE grating acuity training (30 hours) failed to improve grating acuity in both groups. Neither did it produce further AE acuity and stereoacuity gains. Altogether, the stereoacuity gain was associated with pre-training interocular suppression but not with a reduction of interocular acuity di?erence in most amblyopes.
CONCLUSIONS: Dichoptic training can improve and even restore some juvenile amblyopes’ stereoacuity, especially those with mild amblyopia. The dissociation of stereoacuity gain and change of interocular acuity difference suggests that the stereoacuity gains may not result from reduced interocular suppression in most amblyopes, rather the amblyopes may have learned to better readout the stimulus information to improve stereopis.