Sickle cell disease is a hemoglobinopathy affecting mostly African Americans. Sickle cell disease actually was selected for through natural selection in parts of Africa because patients with mild sickle cell disease were very resistant to malaria and survived to reproduce. Several genotypes occur: AC, SA, SS, SC, & Sthal where A is normal hemoglobin and the others are abnormal variants. Abnormals are due to improper amino acid substitution.
Sickle Cell
The red blood cells of sickle cell patients take on a sickle shape instead of the normal bi-concave disc. They become trapped in the small vessels leading to ischemia, hypoxia, and tissue necrosis. The hypoxia leads to more sickling and a cycle is created.
Patients often require spleenectomies, and the disease can be fatal. SS patients have the worst systemic complications while SC and Sthal patients have the most severe ocular problems. This is because the blood is more viscous in these patients and the small retinal arterioles occlude more easily.
Sickle cell retinopathy progresses through five stages.
|
Sickle Cell Stages |
|
Stage I | peripheral arteriolar occlusions |
|
Stage II | peripheral arterio-venular anastomoses |
|
Stage III | neovascularization |
|
Stage IV | vitreous hemorrhage |
|
Stage V | retinal detachment |
Sickle Cell Retinopathy
- Pre-proliferative retinal findings include salmon-patch hemorrhages, black sunburst pigment, intraretinal refractile bodies, and silvering of peripheral arterioles.
- Proliferative findings include sea-fan neovascularization, vitreous hemorrhages, and retinal detachments.
- Other associated findings include venous tortuosity, retinal holes, CRAO, and angioid streaks.
- Treatment consists of PRP or cryotherapy applied to the peripheral areas of retinal ischemia, usually anterior to the sea fans.
|
