SICKLE CELL RETINOPATHY

Sickle cell retinopathy is the general term applied to retinal vascular lesions resulting from hemoglobin (Hb) mutations SS, SC, and Sthal. Ocular manifestations of sickle cell disease are most commonly observed in SC disease. The Hb AS and AC mutations rarely cause ocular changes. Sickle cell retinopathy is characterized by an occlusive vasculopathy as a result of intravascular sickling, hemolysis, hemostasis, and thrombosis. Both nonproliferative and proliferative features occur.

Symptoms

The symptom complex in sickle cell retinopathy resembles that of diabetic retinopathy and radiation retinopathy: patients have reduced central vision due to macular ischemia or vitreous floaters due to neovascularization and vitreous hemorrhage. In all of these disorders, patients can have substantial lesions before symptoms develop.

Clinical Features

Vascular beds throughout the eye can be involved from the conjunctiva to the retina. The retinal lesions include salmon patch hemorrhages, black sunburst pigmentation, and iridescent deposits or “spots,” and the retinal depression sign. Salmon patch hemorrhages are intraretinal hemorrhages following retinal arteriolar occlusion. Black sunburst lesions represent localized areas of retinal pigment epithelial hypertrophy and hyperplasia. Iridescent spots are areas of hemosiderin deposition within the retina in acquired schisis cavities beneath the internal limiting membrane following intraretinal hemorrhage resorption. Capillary occlusion in the macula may result in visual loss. Capillary occlusion in the midperipheral and peripheral fundus may lead to neovascularization. The neovascularization often assumes a “sea fan” appearance. Neovascular sea fans often undergo spontaneous autoinfarction; they may be associated with vitreous hemorrhage and traction retinal detachment. Patients may develop central or branch retinal artery occlusions. Angioid streaks may be observed in individuals with Hb SS disease.

Ancillary Testing

Fluorescein angiography reveals areas of macular and peripheral retinal nonperfusion. Areas of neovascularization hyperfluorescence intensely and may be seen at the junction of perfused and nonperfused retina.

Pathology/Pathogenesis

In sickle cell hemoglobin, the valine is substituted for glutamic acid at the sixth position in the -polypeptide chain. The single amino acid substitutions alter the hemoglobin conformation and the deformability of erythrocytes, thus impeding migration through capillaries. The gene is located on 11p15 in the -globulin complex.

Treatment/Prognosis

Laser photocoagulation may be applied peripheral to areas of retinal neovascularization to reduce the risk of vitreous hemorrhage and traction retinal detachment. Spontaneous regression or autoinfarction of retinal neovascularization may occur, reducing the need for laser treatment. Vitrectomy can be performed to clear vitreous hemorrhages or repair traction retinal detachments. Scleral buckling surgery may be associated with a risk of anterior segment ischemia. The systemic hematologic condition should be stabilized preoperatively.

The visual prognosis is variable but generally favorable. The visual prognosis is worse in patients with

Hb SC and Sthal disease compared to those with SS mutations. Sickle SS disease is associated with angioid streaks and has more systemic complications.

Patients with traumatic hyphema and sickle hemoglobinopathies have a greater risk of rebleeding, glaucoma, and optic nerve damage than do normal subjects. Therefore, patients with African or Mediterranean heritage should undergo hemoglobin electrophoresis

in the setting of hyphema.

Systemic Evaluation

Hemoglobin electrophoresis is indicated to obtain a correct genetic diagnosis.

This fundus photograph demonstrates several of the characteristic findings of sickle cell retinopathy: salmon patch hemorrhages, black sunbursts, and iridescent crystals.

Proliferative sickle cell retinopathy is characterized by the presence of retinal neovascularization that assumes a “sea fan” appearance.

SELECTED REFERENCES

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Eales’ Disease

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Hypertensive Retinopathy

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Leukemic Retinopathy

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Ocular Ischemic Syndrome

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Pregnancy-Related Retinal Disease

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Radiation Retinopathy

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Retinal Arterial Macroaneurysms

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Retinopathy of Prematurity

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Sickle Cell Retinopathy

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