Sicke cell disease (SCD) is a genetically determined hemoglobinopathy. Hemoglobin is a key protein of the erythrocyte, responsible for oxygen transport in the blood. SCD causes erythrocyte dysfunction with reduced blood flow, increased blood clots, tissue hypoxia and eventual pathology. Erythrocytes have a shortened life, which in some conditions may cause hemolytic anemia. All parts of the body, including the eye, may be affected by vascular complications. Proliferative retinopathy and sequelae are a risk in the eye.
Inheritance of SCD is autosomal codominant, with each parent providing one gene for the abnormal hemoglobin. The genotypes are:
- Normal hemoglobin (AA globin genotype)
- Sickle cell anemia (SS) – this form has the most systemic symptoms and proliferative retinopathy may occur in up to 20% of patients
- Sickle cell disease (SC) – proliferative retinopathy may develop in up to 40% of patients
- Sickle cell thalasemia (S Thal) –
- Sickle cell trait (AS) – this form has the fewest systemic complications
Systemic Signs And Symptoms
Chronic anemia, fatigue, jaundice, crisis (extended periods of skeletal and abdominal pain) and chest pain due to pulmonary infarction.
Blurring of vision
- Anterior signs include iris atrophy and neovascularization, bulbar conjunctiva comma-shaped vessels
- Non-proliferative signs include
- black sunbursts (RPE hyperplasia secondary to deep retinal vascular occlusions),
- salmon patch lesions (intraretinal hemorrhages)
- angioid streaks,
- arterial or venous occlusions,
- macular microvascular occlusions
- Proliferative retinopathy, has a standardized classification:
- Peripheral retinal arteriolar occlusions
- Peripheral arteriovenous anastomoses
- Neovascular proliferation: Neovascular fronds, known as sea fans are diagnostic of SCD
- Vitreous hemorrhage from neovascular membranes
- Retinal detachment from severe vitreous traction
Common (approximately 1/100) in people with African descent, no gender bias
Proliferative retinopathy is sight threatening, requiring prompt management
Diabetic retinopathy, Vascular occlusions, Ocular ischemic syndrome, Sarcoidosis
Sickledex, sickle prep and plasma hemoglobin electrophoresis are useful in SCD
Genetic assessment and counseling should be undertaken (see above).
Fluorescein angiography is useful for assessment of proliferative disease or choroidal neovascularization associated with angioid streaks and to guide pan-retinal photocoagulation
SCD requires systemic management that may include blood transfusions, antiplatelet therapy, anticoagulationa and thrombolytic agents. Oral carbonic anhydrase inhibitors or IV mannitol are contraindicated for glaucoma therapy as they may precipitate a systemic crisis
Argon laser panretinal or sector photocoagulation may be indicated for proliferative disease
Vitrectomy may be beneficial for persistent vitreous hemorrhage or retinal detachment. Scleral buckling may also be required for retinal detachment, although there is an increased risk of complications related to ocular ischemia in SCD patients.
Physical activity or dehydration may precipitate systemic sickle cell crisis
Patients at risk of proliferative retinopathy should be reviewed at 6 month intervals
Fan-shaped peripheral retinal neovascularization in an area of non-perfused retina (left). Figure courtesy of Yanoff & Duker Ophthalmology 2nd edn, Elsevier.
“Salmon patch” intraretinal hemorrhage in the equatorial retina. These peripheral hemorrhages may cause retinoschisis cavities seen with iridescent spots, or may enter the subneural retinal space and lead to RPE pigment (black sunburst) lesions. Figure courtesy of Yanoff & Duker Ophthalmology 2nd edn, Elsevier.