Coats disease is a predominantly unilateral, idiopathic, nonhereditary, congenital retinal vascular abnormality.

A variant of type 1 macular telangiectasia; it involves telangiectasias of small- and medium-sized retinal blood vessels without vitreoretinal traction.¹

Males in their first or second decade of life are typically affected, with an earlier onset portending a worse visual prognosis.

Vascular leakage typically leads to a peripheral exudative retinal detachment, most commonly in the inferior and temporal quadrants.

Coats disease is staged according to the funduscopic presence of telangiectasias, exudates, foveal involvement, and exudative retinal detachment. Progression to end stage is characterized by total retinal detachment, glaucoma, and phthisis.

Other characteristic findings include light bulb aneurysms, vascular sheathing, and vascular beading.

Fluorescein angiography can demonstrate leakage from peripheral and macular telangiectatic vasculature. Capillary rarefaction and nonperfusion may be seen. Fellow eyes may demonstrate mild, asymptomatic peripheral vascular abnormalities.²

A vision-threatening exudative maculopathy occurs in about a quarter to 40% of patients. Later in the disease course, macular fibrosis appears as a dull-gray sheet or nodule and is associated with visual loss.

Treatment options for the exudative maculopathy include cryotherapy and laser photocoagulation to areas of telangiectatic, leaking vessels, and intravitreal anti-vascular endothelial growth factor therapy.

Various permutations of vitreoretinal surgery including pars plana vitrectomy, cryotherapy, laser photocoagulation, intraocular tamponade, and external drainage of subretinal fluid may be employed in cases with exudative retinal detachment.

Despite therapy, poorer visual prognosis is correlated to increased disease stage. Advanced-stage eyes may require enucleation.³,⁴

Even in eyes without obvious macular involvement on fundus examination, optical coherence tomography (OCT) imaging can reveal intraretinal fluid, intraretinal exudates, subretinal fluid, subretinal exudates, and disruption of the external limiting membrane and ellipsoid zone.⁵

Outer retinal layer disruption and subfoveal hyperreflective nodules (sharply demarcated hyperreflective subfoveal lesions with posterior shadowing) are associated with poorer visual prognosis.⁶

Macular atrophy and fibrosis may develop in up to 50% of cases despite therapy. The presence of subretinal fluid or subretinal exudates at baseline has been associated with higher likelihood of macular fibrosis development in retrospective study (Figures 16.1, 16.2, 16.3, 16.4, 16.5).⁷

Qualitative changes on optical coherence tomography angiography (OCTA) include capillary telangiectasias, aneurysms, nonperfusion, and dilatation in both the superficial and deep vascular plexuses (SCP and DCP).