Coats disease is a chronic, progressive disorder that affects the retina, the light-sensitive nerve layer at the back of the eye. Coats disease is an abnormal growth spurt of the small blood vessels (capillaries) that nourish the retina. The fragile abnormal vessels break and leak the clear serum part of the blood into the retina, causing the retina to swell.

Coats disease usually affects children (especially boys) in the first ten years of life, but it can also affect young adults. The condition affects central vision, typically in only one eye. Severity can range from mild vision loss to total retinal detachment and blindness. No cause has yet been identified for Coats disease.

The leaking blood vessels can be treated with laser surgery or cryotherapy (freezing). If the retina is detached, a vitrectomy to replace the vitreous (the clear gel-like substance inside the eye) with a gas bubble may be necessary to restore vision.

(c) 2007 The American Academy of Ophthalmology