Ophthalmic assessments of 120 patients with homozygous sickle cell (SS) disease and of 222 with sickle cell haemoglobin-C (SC) disease were conducted over a period of ten years. Visual acuity loss (V.A. less than or equal to 6/18) attributable to sickle cell retinopathy occurred in 10% of untreated eyes during a mean observation period of 6.9 years. Visual loss was strongly associated with proliferative sickle retinopathy (p less than 0.001) and most commonly resulted from vitreous haemorrhage, tractional retinal detachment and epiretinal membranes. The incidence of visual loss was 31 per 1000 eye-years observation among eyes with proliferative disease compared to 1.4 per 1000 eye-years observation among eyes with non-proliferative disease.