Randomised trial of three treatments for amblyopia: Vision therapy and patching, perceptual learning and patching alone

Abstract

Background: Active vision therapy for amblyopia shows good results, but there is no standard vision therapy protocol. This study compared the results of three treatments, two combining patching with active therapy and one with patching alone, in a sample of children with amblyopia.

Methods: Two protocols have been developed: (a) perceptual learning with a computer game designed to favour the medium-to-high spatial frequency-tuned achromatic mechanisms of parvocellular origin and (b) vision therapy with a specific protocol and 2-h patching. The third treatment group used patching only. Fifty-two amblyopic children (aged 4-12 years), were randomly assigned to three monocular treatment groups: 2-h patching (n = 18), monocular perceptual learning (n = 17) and 2-h patching plus vision therapy (n = 17). Visual outcomes were analysed after 3 months and compared with a control group (n = 36) of subjects with normal vision.

Results: Visual acuity (VA) and stereoacuity (STA) improved significantly after treatment for the three groups with the best results for patching plus vision therapy, followed by monocular perceptual learning, with patching only least effective. Change in the interocular difference in VA was significant for monocular perceptual learning, followed by patching. Differences in STA between groups were not significant. For VA and interocular differences, the final outcomes were influenced by the baseline VA and interocular difference, respectively, with greater improvements in subjects with poorer initial values.

Conclusions: Visual acuity and STA improved with the two most active treatments, that is, vision therapy followed by perceptual learning. Patching alone showed the worst outcome. These results suggest that vision therapy should include monocular accommodative exercises, ocular motility and central fixation exercises where the fovea is more active.

Keywords: amblyopia; monocular perceptual learning; patching; stereoacuity; vision therapy; visual acuity.

FIGURE 1

Flowchart of the study describing the randomisation process. CG, control group. RCT, randomised clinical trial.

FIGURE 2

Example of achromatic schematic sad (left) and smiling (right) face and noisy background for the Monocular Perceptual Learning task. The smiling or sad faces appeared randomly.

FIGURE 3

Passing–Bablok scatter diagrams for baseline (pre) and post‐treatment values of visual acuity (VA), stereoacuity (STA) and interocular difference in VA (IOD‐VA). Also indicated are the regression line (solid line), the confidence interval for the regression line (dotted line, short strokes) and the identity line (x = y, dashed line, long strokes). Panels (a–c) show data for the control group (open circles). Spearman's correlations were strong for VA (ρ = 0.84; p < 0.001) and IOD‐VA (ρ = 0.75; p < 0.001) but weak for STA (ρ = 0.28; p = 0.07). Panels (d–f) show the effects for the three treatment groups (x, patching group; ◽ monocular perceptual learning group; ∆ patching + vision therapy group). Spearman's correlations were moderate for VA (ρ = 0.57; p < 0.001) and strong for STA (ρ = 0.89, p < 0.001) and IOD‐VA (ρ = 0.72, p < 0.001).