BackgroundSome data suggest that low levels of low-density lipoprotein cholesterol (LDL-C) are associated with risk of cataracts. Proprotein convertase subtilisin–kexin type 9 (PCSK9) inhibitors reduce LDL-C below levels achieved with statins alone. We determined whether the incidence of cataracts was influenced by treatment with the PCSK9 inhibitor alirocumab versus placebo, and whether that incidence was affected by achieved LDL-C levels.MethodsThe ODYSSEY OUTCOMES trial (NCT01663402) compared alirocumab with placebo in 18,924 patients with recent acute coronary syndrome receiving high-intensity or maximum-tolerated statin. Incident cataracts were pre-specified events of interest. In multivariable analysis using propensity score-matching on characteristics including cataract risk factors, incident cataracts were compared in the alirocumab and placebo groups according to LDL-C levels achieved with alirocumab.ResultsOver median follow-up of 2.8 years (interquartile range 2.3 − 3.4), the incidence of cataracts was similar with alirocumab (127/9462 [1.3%]) versus placebo (134/9462 [1.4%]); hazard ratio [HR] 0.94, 95% confidence interval [CI] 0.74 − 1.20). In patients treated with alirocumab with ≥ 2 LDL-C values < 25 mg/dL (0.65 mmol/L), the incidence of cataracts was 71/4305 (1.6%), versus 60/4305 (1.4%) in propensity score-matched patients from the placebo group (HR 1.10, CI 95% 0.78 − 1.55). In patients treated with alirocumab with ≥ 2 LDL-C values < 15 mg/dL (0.39 mmol/L), the incidence of cataracts was 13/782 (1.7%), versus 36/2346 (1.5%) in matched patients from the placebo group (HR 1.03, CI 95% 0.54 − 1.94).ConclusionTreatment with alirocumab versus placebo, added to statin, did not influence the incidence of cataracts, even when achieved LDL-C levels on alirocumab were very low. Longer follow-up studies might be necessary to exclude the long-term effects on the incidence or progression of cataracts.Trial registrationClinicalTrials.gov Identifier:NCT01663402.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12886-023-03012-1.