Association of hydroxyurea use and sickle cell retinopathy: A systematic review and meta-analysis

Hydroxyurea (HU) is prescribed to reduce systemic complications of sickle cell disease; however, its association with sickle cell retinopathy (SCR) remains unclear. This meta-analysis (PROSPERO: CRD420251079006) evaluates the pooled association between HU use and SCR. In the primary analysis, HU use was not associated with a statistically significant reduction in SCR (OR = 0.90, 95% CI [0.41, 1.97], p = 0.79; I² = 77%). In a prespecified leave-one-out analysis, exclusion of the outlier study did not produce a statistically significant association, although the estimate shifted toward a stronger protective effect with reduced heterogeneity (OR = 0.70, 95% CI [0.39, 1.27], p = 0.25; I² = 67%). In a subgroup analysis excluding high-risk-of-bias studies, HU use was also not associated with a statistically significant reduction in SCR (OR = 0.84, 95% CI [0.39, 1.82], p = 0.66; I² = 77%). In post hoc analyses, HU use was not associated with a statistically significant reduction in SCR in non-adult populations (OR = 1.14, 95% CI [0.43, 3.05], p = 0.79; I² = 81%) or genotype-restricted analyses (OR = 1.22, 95% CI [0.81, 1.84], p = 0.35; I² = 0%). In post hoc analyses restricting studies to retinopathy phenotype, however, HU was associated with statistically significant lower odds of non-proliferative SCR (OR = 0.73, 95% CI [0.54, 0.98], p = 0.04; I² = 0%) and proliferative SCR (OR = 0.24, 95% CI [0.09, 0.60], p = 0.002; I² = 12%). Very low-certainty evidence suggests mixed associations between HU and SCR. Prospective studies are needed to clarify its role in SCR prevention.