Ocular symptoms are uncommon in the early stages of the disease. Systemically, symptoms include painful crises of abdominal and musculoskeletal discomfort. 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 examination 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. Diagnostic tests, such as a fluorescein angiogram, will aid in findings early ocular manifestation of sickle cell disease. People with sickle cell disease should have annual dilated eye examinations beginning at childhood.
The treatment goal for sickle cell retinopathy is to reduce the risk of, prevent, or eliminate retinal neovascularization. Patients who are asymptomatic should have annual dilated eye examinations to monitor for early ocular manifestation. There are two types of ocular manifestation that can occur; nonproliferative, which is the less advanced stage, and proliferative, which is the advanced stage(s).
Nonproliferative ocular manifestations of sickle cell disease include conjunctival vascular occlusions which transform smooth vessels into comma-shaped fragments, iris atrophy, retinal “salmon patch” hemorrhages, retinal pigmentary changes, and other abnormalities of the retinal vasculature, macula, choroid, and optic disc. These clinical findings are readily apparent on dilated eye examinations and all occur due to local vaso-occlusive events but rarely have visual consequences.
Progression to the proliferative stage involves the growth of abnormal vessel fronds which predispose to vitreous hemorrhage and retinal detachment. The initiating event in the pathogenesis of proliferative disease is thought to be peripheral retinal arteriolar occlusions. There are five stages to proliferative retinopathy:
- Stage 1 — Peripheral retinal arteriolar occlusions.
- Stage 2 — Peripheral arteriovenous anastomoses.
- Stage 3 — Neovascular fronds known as sea fans.
- Stage 4 — Vitreous hemorrhage as tractional forces and vitreous collapse, tearing fragile neovascular membranes.
- Stage 5 — Advanced disease identified by severe vitreous traction, non-clearing vitreous hemorrhage, and retinal detachment.
Treatment is reserved for eyes that have progressed to the proliferative stage, thus being at risk for severe visual loss from bleeding and retinal detachment. The goal is aimed at inducing regression of neovascular tissue before progression to bleeding and retinal detachment. Techniques such as laser photocoagulation have been used to cause involution of neovascular lesions. This has the fewest side effects. Specific methods of laser application include direct coagulation of feeder vessels, local scatter photocoagulation with and without focal ablation of the neovascular frond, and 360 degrees of peripheral scatter delivery.
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 moderate 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 (glaucoma).