BackgroundObesity is considered a risk factor for cataracts. The association between weight loss and a cataract among patients with obesity has not been assessed to date.ObjectivesTo assess the association between weight loss following bariatric surgery and cataracts.SettingNationwide Swedish healthcare registries between 2006 and 2019.MethodsWe performed a population-based cohort study. Patients aged 40-79 years who underwent bariatric surgery were matched on their propensity score (PS) to up to 2 patients with obesity ("unexposed patients"). Cox proportional hazard regression analyses calculated hazard ratios (HRs) and 95% confidence intervals (CIs) of developing cataracts following bariatric surgery, compared with unexposed patients. Subgroup analyses by age, sex, bariatric surgery type, and duration of follow-up were conducted.ResultsIn total, 22,560 bariatric surgery patients were PS-matched to 35,523 unexposed patients. The risk of cataracts was decreased in bariatric surgery patients compared with unexposed patients (HR .71, 95% CI .66-.76). We observed the lowest risk of cataracts among bariatric surgery patients aged 40-49 years (HR .52, 95% CI .44-.75) but a null result for patients aged ≥60 years. Gastric bypass or duodenal switch were associated with decreased risks of cataracts, whereas sleeve gastrectomy yielded a null result. Subgroups of sex and duration of follow-up showed no evidence of effect modification (hazards were proportional throughout follow-up).ConclusionOur results suggest that substantial weight loss following bariatric surgery is associated with a decreased risk of cataracts, especially if bariatric surgery was performed before age 60.