Sickle Cell Retinopathy
Seen mostly in blacks, this disease is an inherited disorder involving abnormal hemoglobin, the principal protein of erythrocytes. Normal erythrocytes appear as pliable, biconcave discs, in sickle cell disease they lose their biconcave shape. The sickled cells become rigid and restrict blood flow, causing hypoxia. Tissues deprived of oxygen then undergo pathologic changes.
Sickle cell retinopathy, like diabetic retinopathy, may be proliferative or non–proliferative. Non–proliferative sickle cell retinopathy represents necrosis of retinal vessel walls. Findings include dark–without–pressure, intraretinal (Salmon–patch) hemorrhages, hemosiderin deposits combined with RPE hyperplasia (Black sunburst), venous tortuosity and angioid streaks (with possible choroidal neovascularization).
Proliferative sickle retinopathy results from peripheral arteriolar occlusion. Hypoxia leads to neovascularization with a “Sea fan” appearance. Fibrotic proliferation and scaffolding associated with the neovascularization can lead to vitreal hemorrhage and tractional retinal detachment. 39 Often, the neovascularization will spontaneously regress, leaving a characteristic whitish tuft. 40.
The Sickledex test as well as hemoglobin electrophoresis can be helpful. Non–proliferative retinopathy requires only observation. Refer those with proliferative retinopathy for possible laser treatment.
Patients with retinal macroaneurysms are typically in the 50–80 age range, female and hypertensive. 41, 42 The condition involves a focal dilatation of a major retinal arterial (or, rarely, venous) branch.
Weakening of the vessel wall leads to the aneurysm. There’s no associated microvasculopathy as seen in diabetic retinopathy, but there is a strong association with hypertension. The condition is less commonly associated with retinal embolization, arteriosclerosis and cardiovascular disease.
Patients are frequently asymptomatic, but if the macula is involved they will present with reduced visual acuity and field. 41, 42 Often there is significant leakage, with exudates and extensive intraretinal or subretinal hemorrhage around it. The vascular dilatation may be obscured by hemorrhage. Fluorescein angiography can aid in this diagnosis. The aneurysm will hyperfluoresce early with a balloon–like appearance.
Asymptomatic, non–leaking macroaneurysms simply require monitoring every 4–6 months. If hemorrhage or exudation occurs but does not threaten the macula, monitor every 1–3 months. If hemorrhage does involve or threatens the macula, or if macular edema persists, photocoagulation may be indicated. The laser treatment scleroses the macroaneurysm but leaves the vessel patent. If a non–hemorrhaging macroaneurysm spontaneously pulsates, photocoagulation may prevent rupture. Since these patients have a predilection for systemic vascular disease, refer for evaluation.