Coats disease


Idiopathic retinal vascular disorder with retinal telangiectasia with intraretinal and/or subretinal exudation without appreciable retinal or vitreal traction.

History:

George Coats first described this condition in 1908 as unilateral retinal vascular abnormality with exudation occurring in young males. Subsequently, Leber reported another entity characterized by multiple retinal aneurysms, associated with retinal degeneration. In 1955, Reese described the similarities between Coats disease and Leber miliary aneurysms and concluded that they represent a spectrum of the same disease with the underlying pathology being retinal telangiectasia leading to progressive exudation and retinal detachment.


Pathophysiology

Breakdown of blood retinal barrier (BRB):

Due to changes at the endothelial level of the retinal vasculature.

Plasma leaks into the vessel wall resulting in thickening and “sausage-like” shape of vessels.

Presence of abnormal pericytes

Abnormal pericytes, which along with the damaged endothelium causes bulging of the vessels and the characteristic telangiectasia

The damaged vasculature often rests in a bed of relative retinal ischemia. Exudation of lipids from these vessels is responsible for retinal detachment, retinal thickening, and retinal cyst formation.


Presentation

Unilateral involvement in young males is the typical presentation with most cases being diagnosed in the first and second decade of life. Younger the patient, more severe is the presentation and poorer the visual outcome.

Retinal vascular features:

  • Vision loss
  • Strabismus
  • Xanthocoria
  • Nystagmus
  • Pain

Anterior segment findings:

  • Corneal edema, megalocornea, shallow anterior chamber, anterior chamber cholesterolosis, neovascularization of iris and resultant iris heterochromia, and cataract.

Complications:

Most of the complications are secondary to chronic retinal detachment.
  • Neovascular glaucoma with iris and angle neovascularization
  • Anterior chamber cholesterolosis: Result of migration of cholesterol crystals from exudates in subretinal space into anterior chamber
  • Retinal and vitreous hemorrhage (3% cases)
  • Retinal macrocysts (degenerative changes)
  • Vasoproliferative tumor (vascular mass in the fundus developing in response to chronic retinal detachment)
Advanced Coats with total exudative retinal detachment and intraretinal hemorrhage around peripheral telangiectatic vessels
Advanced Coats with total exudative retinal detachment and intraretinal hemorrhage around peripheral telangiectatic vessels | Sen, M., Shields, C. L., Honavar, S. G., & Shields, J. A. (2019). Coats disease: An overview of classification, management and outcomes. Indian journal of ophthalmology, 67(6), 763–771. https://doi.org/10.4103/ijo.IJO_841_19

Diagnosis

Fundus examination:

  • Light bulb telangiectasias” because of the bulbous terminal configuration and associated extensive yellow exudation
  • Retinal detachment
Retinal telangiectasia and subretinal exudation characteristic of Coats disease
Retinal telangiectasia and subretinal exudation characteristic of Coats disease | Sen, M., Shields, C. L., Honavar, S. G., & Shields, J. A. (2019). Coats disease: An overview of classification, management and outcomes. Indian journal of ophthalmology, 67(6), 763–771. https://doi.org/10.4103/ijo.IJO_841_19

Fluorescein angiography (FFA):

  • Idiopathic retinal telangiectasia as a ‘light bulb appearance
  • Peripheral nonperfusion
  • Other features: Irregular retinal vessel dilatations, retinal vessel tortuosity, areas of capillary non-perfusion, intra- and/or subretinal exudation and retinal detachment
Fluorescein angiogram reveals several areas of hyperfluorescence from leaking retinal telangiectasia, giving a typical ‘light bulb’ appearance | Rishi, P., Rishi, E., Uparkar, M., Sharma, T., Gopal, L., Bhende, P., Bhende, M., Sen, P. R., & Sen, P. (2010). Coats’ disease: an Indian perspective. Indian journal of ophthalmology, 58(2), 119–124. https://doi.org/10.4103/0301-4738.60081

Differential diagnosis:

  • Retinoblastoma
  • Toxocariasis
  • Persistent fetal vasculature syndrome
  • Retinitis pigmentosa with Coats-like reaction
  • Diseases with vascular changes at the vitreoretinal interface (retinopathy of prematurity, familial exudative vitreoretinopathy, incontinentia pigmenti)
Pupillary reflex in Coats and retinoblastoma. (a) Xanthocoria in a child with Coats disease. (b) leukocoria in a child with endophytic retinoblastoma | Sen, M., Shields, C. L., Honavar, S. G., & Shields, J. A. (2019). Coats disease: An overview of classification, management and outcomes. Indian journal of ophthalmology, 67(6), 763–771. https://doi.org/10.4103/ijo.IJO_841_19

Management

Aim of management is to address and eradicate the telangiectatic vessels in order to control and cause resolution of intra- and subretinal exudates and ultimately salvage the globe with preservation of vision.

  • Cryotherapy
  • Laser photocoagulation
  • Anti-VEGF therapy

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