highly significantp < 0.001
Six studies on vision impairment reported a pooled OR of 1.60 (95% CI 0.95–2·70; p = 0.08, I 2 = 69.9%); leave-one-out meta-analysis found removal of a single outlying study left a highly significant OR (OR 1.90, 95% CI 1.65–2.19; p < 0.001).