24.1 Features
Sickle cell retinopathy (SR) is more common among patients who have the SC or SThal genotype than those with the SS genotype. One study estimated the lifetime incidence of proliferative sickle cell retinopathy (PSR) to be 33, 14, and 3% in Hemoglobin SC, SThal, and SS, respectively. Patients with any of those hemoglobinopathies are prone to red blood cell (RBC) sickling due to polymerization of the abnormal hemoglobin molecules after deoxygenation. These sickled cells increase blood viscosity and hypercoagulability, predisposing patients to occlusive thrombosis in organs throughout the body, including the eye. Occlusion of retinal arterioles leads to downstream capillary nonperfusion and subsequent neovascularization (NV).
24.1.1 Common Symptoms
SR patients are frequently asymptomatic. As the disease progresses, patients may become symptomatic with floaters, photopsias, or dark “curtains” in visual fields. Significant vision loss is possible but uncommon.
24.1.2 Exam Findings
The Goldberg classification system outlines the pathophysiological progression of SR and the exam findings that are associated with each stage (▶ Fig. 24.1). The findings of SR are generally divided into those associated with non-PSR and PSR. Each of the descriptive stages can overlap.
Fig. 24.1 Schematic illustrations of pathologic findings seen in sickle cell retinopathy according to the Goldberg classification system. The top row of images corresponds to retina drawings, while the bottom row of images corresponds to typical fluorescein angiography findings.
Nonproliferative Sickle Cell Retinopathy
Stage 1: peripheral arterial occlusion (▶ Fig. 24.2).
Caused by high viscosity of blood in patients with sickled RBCs.
Most easily seen on angiography, but “silver wiring” of permanently occluded peripheral arterioles may be visualized.
Fig. 24.2 (a) Ultra-widefield color fundus photograph of a left eye demonstrating (b) a black sunburst lesion (c) and a focus of superotemporal fibrovascular tissue likely representing a regressed sea-fan. (c) Late-phase ultra-widefield fluorescein angiogram of the same eye demonstrating peripheral nonperfusion and leakage from areas of neovascularization in the superotemporal peripheral retina. (d) Late-phase ultra-widefield fluorescein angiogram of the same eye demonstrating mild leakage from inferotemporal arteriovenous fistulas, formed to bypass ischemic capillary beds.
Stage 2: peripheral arteriovenous anastomoses (▶ Fig. 24.2).
Represent dilated preexisting capillaries.
Usually follow the border of nonperfusion.
Proliferative Sickle Cell Retinopathy
Stage 3: NV and fibrous proliferation (▶ Fig. 24.2).
Classically in a “sea-fan” configuration.
NV usually forms at the border of nonperfusion and grows toward the ora serrata.
Most common location for NV is superotemporal periphery, followed by inferotemporal, and then nasal.
Often NV will autoinfarct due to upstream vascular occlusion, leading to change in their color from red to white.
Stage 4: vitreous hemorrhage.
Caused by traction on newly formed vessels.
Stage 5: tractional retinal detachment (▶ Fig. 24.3).
Usually forms in periphery in areas of NV.
Traction may also result in retinal tears and rhegmatogenous retinal detachment.
Fig. 24.3 (a) Ultra-widefield color fundus photograph of a left eye demonstrating a combined tractional and rhegmatogenous detachment involving all but the nasal retina. Exudate and tractional bands are seen inferotemporally near multiple retinal breaks. Another small break is seen in the periphery superior to the optic disc. (b) Late-phase ultra-widefield fluorescein angiography of the same eye demonstrating leakage from a neovascularization sea-fan lesion inferotemporally which corresponds to the area of exudate and tractional bands in (a).
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