A randomized clinical trial of contrast increment protocols for binocular amblyopia treatment

Abstract

Background: Most clinical trials of contrast-rebalanced binocular amblyopia treatment used a contrast increment protocol of 10% daily with successful play. Paired with a definition of success requiring only 15-30 min/day of gameplay, this increment protocol could allow children to reach 100% fellow eye contrast in 3-9 hours; however, this may not provide adequate therapeutic time with reduced fellow eye contrast. The purpose of this study was to compare the original protocol against three alternative contrast increment protocols designed to increase the number of treatment hours.

Methods: In this prospective study, 63 amblyopic children (4-10 years; amblyopic eye visual acuity, 20/40-125) were randomly assigned one of four daily contrast increment protocols for 4 weeks, all starting with 20% fellow eye contrast: 10%, 5%, 0%, or 10% for first 4 weeks then reset to 20% and repeat 10% increment for the final 4 weeks. Children played contrast-rebalanced games for 1 hour/day, 5 days/week. Best-corrected visual acuity, stereoacuity, and suppression were assessed at baseline and every 2 weeks until the 8-week outcome visit.

Results: At baseline, mean amblyopic eye best-corrected visual acuity was 0.47 ± 0.14 logMAR (20/60), improving overall 0.14 ± 0.08 logMAR (1.4 lines; P < 0.0001) at 8 weeks. All four protocols resulted in similar improvement in visual acuity (0.13-0.16 logMAR; all Ps < 0.0002). Stereoacuity and suppression also improved (all Ps < 0.05).

Conclusions: None of the new protocols resulted in less improvement than the original 10% contrast increment protocol. Contrast-rebalanced binocular games yielded significant improvements in visual acuity, stereoacuity, and suppression with or without daily contrast increments.

Trial registration: ClinicalTrials.gov NCT03288948.

FIG 1.

Consort diagram showing the number of completed and missed visits during the 8-week study period. There were 5 missed follow-up examinations among the 63 children who completed 8-week visit. There were 5 children, excluded from analysis, lost to follow-up between the baseline visit and the 8-week final examination.

FIG 2.

Illustration of hypothetical fellow eye contrast percentage for the four contrast increment protocols over the 8-week study.

FIG 3.

Amblyopic eye best-corrected visual acuity (BCVA) improvement at baseline, 2 weeks, 4 weeks, 6 weeks, and 8 weeks. Error bars represent ± standard error. P values are group differences from baseline.

FIG 4.

Amblyopic eye best-corrected visual acuity (BCVA) at the baseline and 8 weeks for children with 10% contrast increment, 5%, 0%, and 10% + reset. Data points above the line indicate improvement. Overlapping symbols are slightly shifted for clarity.