Coat’s disease is a severe form of retinal telengectasia [idiopathic congenital vascular malformation], which typically affects one eye of boys in their first decade of life.

In early stages it is characterized by large areas of intra and sub retinal yellowish exudates haemorrhages associated with overlying dilated ad tortuous retinal blood vessels and a number of small aneurysms near the posterior pole and around the disc.

It may present with visual loss, strabismus [squint] or leucocoria [opacity of the vitreous presenting as a white pupil].and thus needs to be differentiated from retinoblastoma.

The condition usually progresses to produce exudative retinal detachment and a retrolental mass.

In the late stages, a complicated Cataract, ileitis and secondary glaucoma occur, which eventually end in phthisis bulbi [atrophied Eyeball].

Treatment
Photocoagulation or cryotherapy may check progression of the disease if applied in the early stage. However, once retina is detached the treatment becomes increasingly difficult and successes rate declines to 33%.