J.B. Harlan, Jr. M.D.
Morton F. Goldberg M.D.
Sickle cell vaso-occlusive events can affect every vascular bed in the eye, often with visually devastating consequences in advanced stages of the disease. Since early stages of sickle cell eye disease do not usually result in visual symptoms, the disease can go undetected unless a formal eye exam is performed by an ophthalmologist. The examination should include an accurate measurement of visual acuity, assessment of pupillary reactivity, careful evaluation of the anterior structures of the eye using a slit-lamp biomicroscope, and a thorough examination of the posterior and peripheral retina through a dilated pupil. Patients with sickle hemoglobinopathies should have yearly eye examinations beginning in childhood.
Although peripheral vaso-occlusion may be observed as early as 20 months of age (McLeod), clinically detectable retinal disease is found most commonly between 15 and 30 years of age (Condon & Serjeant). Sickle retinopathy is more common in HbSC disease but can also occur in Hb SS disease and HbSthal (Condon & Serjeant). Observational cohort studies have also shown that stage IV and stage V retinopathy occur more often in HbSC subjects than in those with HbSS (Condon & Serjeant; Clarkson). It is a paradox that despite the less dramatic systemic consequences of their disease, subjects with HbSC and HbSthal are more likely than HbSS patients to have serious ocular manifestations. Current research has not yet been able to explain the reason for this profound discrepancy in the severity of the retinal and systemic manifestations among the various sickle hemoglobinopathies.
Diagnosis of the proliferative retinopathy requires examination through a dilated pupil utilizing wide field indirect ophthalmoscopy Evaluation of retinal blood flow is performed with fluorescein angiography. Any patient identified with retinopathy should be followed by an ophthalmologist who specializes in diseases of the retina.
If retinal detachment and/or non-clearing vitreous hemorrhage is present, surgical intervention is usually required. Surgical techniques include vitrectomy with or without the placement of a scleral buckle. Although modern vitreoretinal microsurgery can improve vision for many patients with advanced sickle retinopathy, it should be emphasized that surgery carries a significant risk of intraoperative and postoperative complications, including severe ocular ischemia, recurrent hemorrhage and elevated eye pressure(Cohen). In order to minimize the risk of such complications, partial exchange transfusion has been recommended prior to surgery (Brazier), usually with a target of about 50%-60% normal red cells, but there has never been a controlled study demonstrating the efficacy of this maneuver (Charache). Exchange transfusion is also not without its own risks, including various immune-mediated transfusion reactions as well as transmission of infectious diseases such as HIV and hepatitis. When considering an exchange transfusion, a thorough discussion of the risks and benefits should take place. An alternative to exchange transfusion is the use of a hyperbaric chamber to increase blood oxygenation (Freilich), but such equipment is neither convenient nor widely available. In any event, intra-operative and post-operative hyper-oxygenation is indicated in an attempt to reduce the risk of anterior segment ischemia and necrosis.
Trauma considerations aside, any sickle patient with an acute change in vision should always be immediately referred to an ophthalmologist for a full evaluation.
Significant resources also continue to be directed towards the study of angiogenesis along with the search for potential anti-angiogenic agents (Aiello; Auerbach; Cao; Fan; ).
to additional information on opthalmological disorders in sickle cell
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