The diagnosis in this issue is proliferative sickle retinopathy with inferior retinal detachment O.D.
Additional optometric tests might have included: gonioscopy to rule out neovascularization of the angle (NVA); 3-mirror retinal examination to identify the extent of the detachment and areas of neovascularization elsewhere (NVE); binocular indirect ophthalmoscopy with scleral depression; automated perimetry; and photodocumentation.
Hemoglobinopathies are among the commonly inherited diseases in humans.1 Hemoglobinopathies result when there is altered structure, function or production of hemoglobin.1,2 Hemoglobin is the principle protein of the erythrocyte, responsible for binding and facilitating oxygen transmission to tissues.1,2 In the four variations of sickle cell disease, systemic and ocular tissues become deprived of oxygen and undergo pathologic changes.
Variations in the alteration of the amino acid sequence on the globin chain produce variations in the diseases expression.1 The four forms of the disease are often referred to by their genotype:1
AS: sickle cell trait
SS: sickle cell anemia
SC: sickle cell disease
SThal: sickle cell thalasemia
Systemically, the sickle cell anemia variation SS produces the most symptoms.1 With respect to the eye, the sickle cell disease mutation SC produces the most effects. Overall, the sickle cell trait expression AS produces the fewest complications.1
Ocular symptoms are uncommon in the early stages of the disease. Systemically, symptoms include painful crises of abdominal and musculoskelatal discomfort. Ocular signs include comma-shaped vessels in the bulbar conjunctiva, iris atrophy, iris neovascularization, dull gray fundus appearance, retinal venous tortuosity, nonproliferative retinal hemorrhages in the subretinal, intraretinal or preretinal position, black sun bursts (retinal pigment epithelial hypertrophy secondary to deep retinal vascular occlusions), glistening refractile deposits in the retinal periphery (hemosiderin-laden macrophages), salmon patch hemorrhages (orange-pink-colored intraretinal hemorrhage), angioid streaks (breaks in Bruchs membrane radiating from the optic nerve), venous occlusion, artery occlusion, peripheral neovascularization (sea-fan retinopathy) and retinal detachment.16
The retinal specialist agreed with our diagnosis and scheduled her for panretinal photocoagulation (PRP) with retinal reattachment surgery using scleral buckling and gas tamponade. Despite her insistence the vision was OK until a time just prior to her examination, the retinal specialist assured all of us this had been present for over eight months.
The origin of the sickling gene can be traced to the continent of Africa. Data suggests that the mutation of the hemoglobin chain protected affected individuals from malaria infection.2 Inheritance of the sickle cell hemoglobinopathies is autosomal codominant, with each parent providing one gene for the abnormal hemoglobin.1 The disease results following the genetic substitution of valine for glutamic acid. Structurally, crystals form in the hemoglobin causing it to deform.
Normal erythrocytes, containing normal hemoglobin, appear as flexible, pliable, biconcave discs. Erythrocytes affected by sickling disease lose their biconcave shape and their ability to efficiently move through the circulatory system. The sickled cells become rigid, restrict blood flow, produce clots, and cause tissues to become hypoxic.1-6
The treatment goal for sickle cell retinopathy is to reduce the risk of, prevent and or eliminate retinal neovascularization. Patients with asymptomatic sickle cell diseasefree of ocular signsshould be followed biannually with ocular examinations and dilated retinal evaluation. Referral to the retinologist is indicated when retinal findings are seen, as visual loss can result from both nonproliferative (subretinal neovascularization secondary to angioid streaks) and proliferative retinal disease.1-6 The treatment for proliferative disease includes fluorescein angiography and panretinal photocoagulation. Cryotherapy has not been proven to be efficacious and is associated with high complication rates.4 Scleral buckling may be indicated in cases of retinal detachment.4
Proliferative sickle cell retinopathy is classically broken down into five stages:1-6
Stage 1 is recognized by peripheral retinal arteriolar occlusions.
Stage 2 is marked by the appearance of peripheral arterio-venous anastamoses.
Stage 3 is characterized by the growth of neovascular fronds known as sea-fans.
Stage 4 is marked by vitreous hemorrhage as tractional forces and vitreous collapse tear fragile neovascular membranes.
Stage 5 is advanced disease, identified by severe vitreous traction and retinal detachment.
Other causes of peripheral neovascularization include sarcoidosis, diabetes, retinal venous occlusion, Eales disease, leukemia and ocular ischemic syndrome.3-6
The laboratory testing for detecting sickle cell disease in patients with suspicious findings includes the Sickledex, Sickle Prep, and plasma hemoglobin electropheresis.3-6
1. Kaiser HM. Hematologic Disease. In: Blaustein BH. Ocular Manifestations of Neurologic Disease. Philadelphia: Mosby, 1996:165-177.
2. Rogers-Philips E, Philips A. Hematology and Oncology. In: Muchnick BG. Clinical Medicine in Optometric Practice. Philadelphia: Mosby, 1994:306-316.
3. Cullom RD, Chang B. Sickle Cell Disease. In: Cullom RD, Chang B. The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease. Philadelphia: J.B. Lippincott Co., 1994:335 -337.
4. Alexander LJ. Retinal Vascular Disorders. In: Alexander LJ. Primary Care of the Posterior Segment, 2nd ed. Norwalk, CT: Appleton and Lange, 1994:171-175.
5. Brown GC. Retinal Vascular Disease. In: Tasman W, Taeger EA. The Wills Eye Hospital Atlas of Clinical Ophthalmology. Philadelphia: Lippincott-Raven, 1996:161-206.
6. Lutty GA, Phelan A, McLeod DS, et al. A rat model for sickle cell-mediated vaso-occlusion in retina. Microvasc Res 1996 Nov;52(3):270-80.
Click here to return to this month"s Diagnostic Quiz.
