Effects of grating stimulation on vision in individuals with amblyopia: a systematic review and meta-analysis

Purpose To investigate the effects of Cambridge Stimulator with grating element stimulation on visual acuity (VA), grating acuity (GA), and contrast sensitivity (CS) in patients with amblyopia. Methods Three electronic databases (PubMed, Embase, and Cochrane Library) were searched for studies published from January 1970 to November 2022. The searched studies were reviewed and extracted independently by two authors. The included studies were evaluated by the Cochrane risk of bias. A meta-analysis calculating Hedges’ g effect-size metric with 95% confidence intervals using random-effects DerSimonian-Laird model was employed. Heterogeneity was estimated using I 2 statistics. Outcomes of interest included VA, GA, and CS. Results A total of 1221 studies were identified. Twenty-four studies including 900 subjects met the inclusion criteria. The outcome measure of all visual indexes (VA: Hedges’ g of − 0.43, 95% CI = − 0.81 to − 0.05, I 2 = 86%, p = 0.02; GA: Hedges’ g of 3.79, 95% CI = 1.05 to 6.54, I 2 = 98%, p = 0.01; CS: Hedges’ g of 0.64, 95% CI = 0.19 to 1.09, I 2 = 41%, p = 0.00) significantly favored in the grating group. Conclusions Grating stimulation may be a positive help for visual functions in patients with amblyopia. The effects of grating stimulation on VA and CS appear to be opposite. This study is registered with www.crd.york.ac.uk/prospero/ (CRD42022366259).