Sickle cell retinopathy

Abstract

Sickle cell disease (SCD) is an autosomal recessive genetic disorder affecting hemoglobin composition. The defective sickle hemoglobin forms rigid polymers in low oxygen conditions, which turn red blood cells into the eponymous sickled shape. These sickled cells can then lead to vaso-occlusion and hemolysis-related endothelial dysfunction. In the eye, sickle cell retinopathy is the most common cause of vision loss in SCD. Sickle cell retinopathy can be categorized into nonproliferative and proliferative changes. Changes in nonproliferative sickle retinopathy (NPSR) include salmon patches, black sunbursts, iridescent spots, and angioid streaks. Proliferative sickle retinopathy (PSR) can cause vision-limiting complications like vitreous hemorrhage and retinal detachment. Risk factors for PSR include older age and the HbSC and HbThal genotypes as compared to HbSS. Sea fan neovascularization in the peripheral retina is the classic finding in PSR. Dilated fundoscopic examinations, fundus photography, and fluorescein angiography have traditionally been the mainstay of sickle cell retinopathy evaluation; however, ultrawide-field imaging, optical coherence tomography (OCT), and OCT angiography (OCT-A) have allowed for improved visualization of peripheral lesions and evaluation of macular microstructure and microvasculature respectively. NPSR findings are typically not visually significant and do not require intervention. Although SCR has traditionally been considered a peripheral retinopathy, sickle cell maculopathy, in which macular thinning on OCT and flow voids on OCT-A are noted, is commonly observed. In PSR, a combination of laser photocoagulation and anti-VEGF injections can be used to regress sea fan neovascularization. Although patients with SCR generally have good vision, patients with PSR who progress to nonclearing vitreous hemorrhage and retinal detachment may experience severe vision loss that requires surgical intervention. Screening guidelines for SCR are based upon expert consensus and recommend dilated eye exams every 1–2 years for patients with SCD starting at age 10. There is a need for updated and data-driven recommendations for SCR screening.