What Is Coats’ Disease?
Coats' disease (CD), also known by its antiquated names exudative retinitis or retinal telangiectasia with exudates (RTOE) is a rare idiopathic retinal vascular disease that involves abnormal vasculature which can lead to retinal detachment and vision loss. It almost exclusively affects young males and is typically diagnosed before age 10, with rare exceptions in late adolescence.
Pathophysiology
CD represents a primary retinal vasoproliferation disorder causing leakage and exudates. There are two stages of CD: a preproliferative stage and an exudative stage. Typically both stages occur, but some cases may only develop the exudative stage.
* Preproliferative stage
- Retinal telangiectasia
- Venous congestion
- Microaneurysms
- Intraretinal and subretinal exudates
- Retinal edema
* Exudative stage
- Extensive subretinal exudates
- Subretinal fibrosis
- Retinal and optic disc detachment
Clinical presentation
Classically, CD is a unilateral vision loss in a young male (average age of onset is 6 years). The patients commonly complain of decreased vision, metamorphopsia, or leukocoria.
- Peripheral exudates that originate in the posterior pole and extend through breaks in the inner retinal layers into the subretinal space where lipid-laden histiocytes absorb the yellow-white exudates.
- Telangiectatic vessels are variably dilated and tortuous retinal venules that sometimes bleed and contribute to the exudation of fluid and the deposition of lipid, resulting in exudative retinal detachments.
- Retinal detachment is the most frequent and the most important feature of CD. As the retinal detachment progresses, the retinal breaks may lead to a rhegmatogenous detachment involving the macula.
- Optic disc edema may also be present
Diagnosis
It is primarily based on clinical appearance. Optical coherence tomography (OCT) can be helpful for diagnosis and monitoring treatment success. Fluorescein angiography is usually not necessary for the diagnosis. It may detect the underlying retinal telangiectasia better but does not provide any more useful information than OCT for making treatment decisions.
Differential diagnosis
The differential diagnosis of CD includes other causes of exudative retinal detachment, including:
Retinoblastoma
Toxocariasis
Familial exudative vitreoretinopathy
Persistent hyperplastic primary vitreous
Incontinentia pigmenti
Idiopathic uveitis
Management
Early detection of CD is essential to prevent profound visual loss. Treatment options for CD include laser, anti-VEGF injections, photodynamic therapy, and cryotherapy.
- Laser photocoagulation is the mainstay of treatment, typically argon or diode laser, to ablate the vascular abnormalities and retinal tears to reduce traction and risk of detachment. Close monitoring is required as the effects of the laser may not be apparent for months. Some patients may require additional laser sessions. Macula-sparing strategies that try to preserve central vision are recommended.
- Anti-VEGF therapy, such as bevacizumab (Avastin), can be used to inhibit VEGF-induced neovascularization and vascular permeability, leading to decreased subretinal fluid and improved visual acuity.
- Cryotherapy is primarily used to address retinal detachments that involve the macula.
- Photocoagulation has less of a role in the management of CD than cryotherapy.
- Scleral buckling may be indicated for large retinal tears or detachments that involve the macula.
- Vitrectomy is typically reserved for cases that have not responded to other treatments or when severe complications are present, such as proliferative vitreoretinopathy (PVR).
Prognosis
With prompt diagnosis and appropriate treatment, much of the vision can be preserved. However, if the disease is not recognized or treated early, extensive retinal detachment and vision loss can occur. Overall, the visual prognosis of Coats disease mostly depends on the timeliness of diagnosis and the extent of the subretinal exudation and retinal detachment.