Recent laboratory findings suggest that short-term patching of the amblyopic eye (i.e., inverse occlusion) results in a larger and more sustained improvement in the binocular balance compared with normal controls. In this study, we investigate the cumulative effects of the short-term inverse occlusion in adults and old children with amblyopia. This is a prospective cohort study of 18 amblyopes (10-35 years old; 2 with strabismus) who have been subjected to 2 hours/day of inverse occlusion for 2 months. Patients who required refractive correction or whose refractive correction needed updating were given a 2-month period of refractive adaptation. The primary outcome measure was the binocular balance which was measured using a phase combination task; the secondary outcome measures were the best-corrected visual acuity which was measured with a Tumbling E acuity chart and converted to logMAR units and the stereoacuity which was measured with the Random-dot preschool stereogram test. The average binocular gain was 0.11 in terms of the effective contrast ratio (z=−2.344, p=0.019, 2-tailed related samples Wilcoxon Signed Rank Test). The average acuity gain was 0.13 logMAR equivalent (t17=4.76, p<0.001, 2-tailed paired samples t-test). The average stereoacuity gain was 339 arc seconds (z=−2.533, p=0.011). Based on more recent research concerning adult ocular dominance plasticity, we conclude that inverse occlusion in adults and old children with amblyopia does produce long-term gains to binocular balance and that acuity and stereopsis can improve in some subjects.

Citation: Tao C, Wu Y, Gong L, et al. Abnormal monocular and dichoptic temporal synchrony in adults with amblyopia. Invest Ophthalmol Vis Sci. 2019;60:4858-4864. https://doi.org/ 10.1167/iovs.19-27893 PURPOSE. We investigate temporal synchrony within one eye and between both eyes in adults with amblyopia. (range, 19.88-27.81 years old; median, 22.86 years old) and 12 age-matched adults with normal vision (range, 21.2-50.30 years old; median, 23.78 years old) participated in the experiment. We showed two pairs of Gaussian blobs flickering at 1 Hz as visual stimuli, one pair with the same temporal phase modulation (i.e., the reference) and another pair with a distinct temporal phase (i.e., the signal). We employed the constant stimuli method to measure the minimum degree of temporal phase (temporal synchrony threshold), at which participants were able to discriminate the signal pair under binocular, monocular, and dichoptic viewing configurations. METHODS. Eight adult amblyopesRESULTS. The temporal synchrony threshold was different across the six configurations (P ¼ 0.001). There was also an interaction between the configuration and the group (P ¼ 0.004). The synchrony threshold was significantly higher in amblyopes than in controls under the configurations where two pairs of blobs were presented to the amblyopic eye (136.52 6 50.19 vs. 97.08 6 22.02 ms, P ¼ 0.027) and where the paired blobs were presented to different eyes (163.15 6 80.85 vs. 111.61 6 22.46 ms, P ¼ 0.049). The visual deficits in these two configurations were significantly correlated (r ¼ 0.824, P ¼ 0.012).CONCLUSIONS. The threshold for detecting temporal asynchrony increased when the stimuli were presented only to the amblyopic eye and when they were dichoptically presented to the amblyopic and fellow eyes.

To assess interocular delays in amblyopes with stereopsis and to evaluate the relationship between interocular delays and the clinical characteristics. METHODS. Twenty amblyopes with stereopsis (median, 400 arcseconds) and 20 controls with normal or corrected to normal visual acuity (≤0 logMAR) and normal stereopsis (≤60 arcseconds) participated. Using a rotating cylinder defined by horizontally moving Gabor patches, we produced a spontaneous Pulfrich phenomenon in order to determine the interocular delays, that is, the interocular phase difference at which ambiguous motion in plane was perceived. Two spatial frequencies-a low (0.95 cycles/degree [c/d]) and a medium (2.85 c/d) spatial frequency-were tested. RESULTS. The absolute interocular delays of the amblyopic group was significantly longer than that of the controls at both low or medium spatial frequencies (P < 0.01). However, the interocular delays was not always in favor of the fellow eye: 35% of the amblyopes (7/20) showed a faster processing of the amblyopic eye than that of the fellow eye at 0.95 c/d and 29.5% (5/17) at 2.85 c/d. No significant correlation was found between interocular delays and the clinical characteristics (e.g., age, treatment history, stereoacuity, and magnitude of anisometropia) in this amblyopic cohort. CONCLUSIONS. The interocular delays in amblyopes with stereopsis might result from either a faster or slower processing of the amblyopic eye relative to the fellow eye. This work provides important additional information for binocular processing of dynamic visual stimuli in amblyopia. However, the special role between this form of interocular delays and patients' clinical characteristics remains unknown.