The affected areas of the retina are at the outer margins, far beyond the region visualized with direct opthalmoscopy. Patients often have sudden vision loss due to a vitreous hemorrhage as the first manifestation of sickle retinopathy. Some patients with hemoglobin SC disease who have had particularly mild manifestations do not realize that they have a sickle syndrome before sudden vision loss. Laser therapy of proliferative retinopathy can save vision for patients with sickle cell disease. Yearly examinations by an ophthalmologist is true health maintenance.
Antibodies can limit the availability of transfusion at times when blood can be life-saving.
A significant cause of rapid alloimmunization is that blood donations are made primarily by people of European background. Minor red cell antigens normally present little problem in transfusion and are therefore not looked for with typing and crossmatching. Some of these antigens, such as Kell, Kidd and Duffy, are expressed at different frequencies in people of African ancestry. Some of these problems can be minimized by extended phenotype matching in which the expression of these minor antigens are determined. The closer the antigens of the transfused blood matches that of the recipient, the less likely that problems will occur.