Coat’s disease is a rare abnormality of the blood vessels in the retina. It is typically diagnosed in the first decade of life and almost always not hereditary. Infrequently, Coats’ disease is diagnosed as late as the eighth decade of life. Younger patients are affected more severely with a more rapid progression. The disease affects only one eye in 90% of cases, and 70% to 90% of affected children are male. No racial or ethnic predisposition or environmental factors have been linked to Coats’ disease.
The cause of the disorder is not clear. It is believed that abnormalities of the blood vessel wall cause leakage of fluid into the retina, producing the characteristic yellow-white intraretinal and subretinal cholesterol exudates (Figure), hemorrhage, and subretinal fluid.
Children typically will present with crossed eyes, a white pupil, or poor vision on routine vision screening. Characteristic retinal findings in Coats’ disease are “light bulb-shaped” dilatations of smaller blood vessels with adjacent exudates. More severe cases can have detachment of the retina which can be total. Although the center of vision (macula) is less frequently involved than the peripheral (outer) retina, massive accumulation of lipid in the macula can form a scar in the center of vision and cause a significant visual deficit. Fluorescein angiography (a photographic dye test to evaluate the blood vessels) is helpful in juvenile Coats’ disease in not only diagnosis but also identifying treatable areas.
Juvenile Coats’ disease must be differentiated from other pediatric retinal conditions that can have a “white pupil” appearance. These conditions include retinoblastoma (Rb), Von Hippel capillary hemangioma, retinopathy of prematurity, familial exudative vitreoretinopathy, persistent fetal vasculature syndrome, ocular toxocariasis, incontinentia pigmenti, pars planitis, and choroidal hemangioma. In cases of retinoblastoma, the age at diagnosis (average age is 18 months) is typically younger than in Coats’ disease. In addition, Rb has no gender predilection, and is found to involve both eyes in one-third of cases from a germline mutation. Ultrasound and radiographic (CT or MRI) findings can help in the diagnosis when retinal detachment or disorganization is a prominent feature. Although not universal, the presence of calcifum suggests retinoblastoma.
If left untreated, eyes with Coats disease deteriorate, often progressing to total retinal detachment (64%) or glaucoma (32%). All abnormal blood vessels identified on fluorescein angiogram are treated with laser or freeze therapy (cryopexy). Multiple treatment sessions are often needed to control the disease. Long-term follow-up at 6 months intervals is necessary as recurrences can occur even after a decade following successful treatment, managed with additional therapy as needed. In cases of retinal detachment, the fluid can be drained from underneath the retina and a support band (scleral buckle) is often placed around the eye.