Updated on  April 30, 2024
6 min read

What Is Coats Disease and How Is It Treated?

5 sources cited
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Coats disease, or exudative retinitis, is the breakdown of the eye blood vessels that provide oxygen and nutrients to the retina. The retina is a thin layer of light-sensitive tissue at the back of the eye.

If left untreated or detected in later stages, Coats disease can lead to more severe conditions, including:

  • Retinal detachment
  • Severe vision loss
  • Permanent blindness

It’s a rare disease that isn’t linked to genetics or family history. It can happen at any age but is most common in men and children younger than eight.

This article will highlight Coats disease’s symptoms, diagnosis, and treatment. We’ll also touch on the different stages of Coats disease and commonly asked questions.

What is Coats Disease?

Coats disease is the development of progressive abnormal blood vessels in the back of the eye that feed into the retina. It usually only affects one eye (unilateral), with only 5% of cases involving both eyes (bilateral). 

This rare eye condition was named after its founder, George Coats. The condition is typically more aggressive in children, with adults presenting with milder disease.1

What Causes Coats Disease?

Coats disease occurs if blood vessels at the back of the eye are abnormally shaped and functioning poorly, causing leakage of proteins and lipids. This leakage leads to the thickening and necrosis of vessel walls, eventually making the retinal blood vessels useless.

The lack of healthy retinal blood flow leads to retinal detachment and increased pressure in the eye (neovascular glaucoma), causing severe vision loss. If a retinal detachment is not treated immediately, it can lead to permanent blindness in the affected eye.

Signs and Symptoms of Coats Disease

Coats disease is a progressive condition typically asymptomatic in its early stages, making it hard to treat early. People have discovered they have Coats during a routine comprehensive eye exam that includes pupil dilation. 

Symptoms typically start after the retinal vessels begin to leak. The most common first sign of Coats disease is decreased visual acuity (sharpness of vision).

Other signs and symptoms of Coats disease include:

  • Strabismus (misalignment of the eyes)
  • Leukocoria (white pupil)
  • Retinal exudation (leaky blood vessels)
  • Total retinal detachment
  • Retinal macrocysts (large cysts on the outer layer of the retina)
  • Vasoproliferative tumor (peripheral retina benign tumor)
  • Retinal neovascularization (new abnormal blood vessel growth)

Severe cases of Coats disease can lead to retinal detachment, a medical emergency.

Symptoms of a retinal detachment include:

  • The sudden appearance of floaters in your field of vision 
  • Flashes of light in one or both eyes
  • A “curtain” coming down over your field of vision 
  • Blurred vision 
  • Vision loss
  • Reduced peripheral vision

Seek immediate medical attention if you have symptoms of a detached retina, as it can lead to blindness if left untreated.

How is Coats Disease Diagnosed?

Coats disease is diagnosed through a series of eye exams and tests. Asymptomatic cases may be discovered during a routine comprehensive eye exam.

Coats disease has symptoms similar to other eye conditions that must be ruled out. 

Other conditions that present similar to Coats in young children include:

  • Retinoblastoma. Cancer of the retina
  • Persistent fetal vasculature. Embryonic blood vessels that don’t go away
  • Familial exudative vitreoretinopathy (FEVR). A group of inherited retinal diseases
  • Retinopathy of prematurity. Abnormal blood vessel growth in premature infants
  • Toxocariasis. Parasitic roundworm infection

Along with a comprehensive eye exam, and health history, eye doctors will use the following clinical assessment tests and scans to help diagnose Coats disease:

  • Fundus Fluorescein Angiogram (FFA). Checks for blood vessel leakage
  • Optical Coherence Tomography (OCT). Looks for blood vessel inflammation, leakage, and thickness
  • Ocular Ultrasonography (USG). Identifies the extent of the retinal detachment
  • Computed Tomography (CT). Helps rule out retinoblastoma
  • Magnetic Resonance Imaging (MRI). Helps diagnose advanced Coats and rule out retinoblastoma

Stages of Coats Disease

Experts have developed a staging system for the progression of Coats disease to help identify severity and secondary complications. The staging system also creates a treatment plan and predicts prognosis.

There are five stages to Coats disease, with stages two and three containing sub-stages: 

Stage 1: Retinal Telangiectasia Only

In stage one, there is evidence of abnormal and broken blood vessels (capillary dilation). In this stage, the blood vessels haven’t started to leak.

Stage 2a: Telangiectasias and Extrafo­veal Exudation

In stage 2a, the doctor can see abnormal blood vessels, which have started leaking plasma into the retina.

Stage 2b: Telangiectasias and Foveal Exudation

Stage 2b is when symptoms of stage 2a are present, but leakage has spread into the fovea. The fovea is the part of the retina that controls central vision.

If large quantities of fluid leak in the fovea, it can trigger changes in your vision.

Stage 3a: Subtotal Exudative Retinal Detachment

During this stage, the retina starts to detach. It can result in a partial or total retinal detachment. 

You will see changes in your vision, including floaters, blurred vision, and changes to your peripheral vision.

Stage 3b: Total Exudative Retinal Detachment

As stage three progresses, the retina completely detaches, causing severe changes in vision, including a “black curtain” that completely blocks your vision.

A total retinal detachment is a medical emergency. If left untreated, it will cause permanent blindness in the affected eye.

Stage 4: Total Detachment with Sec­ondary Glaucoma

If left untreated, a retinal detachment can cause glaucoma, which is increased eye pressure. Both of these conditions are medical emergencies.

The presence of secondary glaucoma means the person is in stage four of Coats disease.

Stage 5: Advanced End-Stage Disease

Stage five is advanced Coats disease. It means that the retina has detached, eye pressure is high, and the eyeball starts to waste away (phthisis bulbi). 

Besides glaucoma, other secondary conditions associated with stage 5 include:

  • Cataracts (clouding of the lens)
  • Uveitis (inflammation inside your eye)
  • Rubeosis iridis (neovascularization)
  • Eye pain

Doctors typically classify the affected eye as blind, and removal of the eye may be necessary.

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What is the Best Treatment for Coats Disease?

There is no cure for Coats disease. However, if caught early, treatment interventions can improve your eyesight and slow the disease’s progression.

Treatment will depend on the stage of the disease. Monitoring the condition may be the only treatment for mild cases that have not developed leakage.

However, a more aggressive treatment plan will be necessary if the disease progresses into blood vessel leakage.

Coats disease treatments include:

  • Laser photocoagulation uses ablation to destroy abnormal tissue. 
  • Cryotherapy is an adjunct treatment using extreme cold to reduce exudation and prevent or repair retinal detachment. 
  • Vitreoretinal surgery- may be used for retinal reattachment or secondary complications.
  • Enucleation- removal of the eye and its intraocular contents.
  • Anti-vascular endothelial growth factor (anti-VEGF) injections are used to control inflammation and reduce the growth of abnormal vessels. 

Who Is at Risk of Coats Disease?

Coats disease hasn’t been linked to family history. While the exact cause is unknown, it tends to affect boys between the ages of 8-16 at a ratio of 3:1 compared to girls the same age. However, it has been diagnosed in infants and adults too.

Researchers have found that many people diagnosed with Coats disease also have a mutation of the Norrie disease protein (NDP) gene. This gene triggers the creation of abnormal new blood vessels. 


Coats disease is a rare disorder that triggers the development of abnormal blood vessels in the retina, leading to fluid leakage, retina detachment, and elevated pressure around the eye. 

While Coats disease is not life-threatening, advanced stages can lead to vision loss and permanent blindness if not caught early. You must seek immediate medical attention if you experience sudden vision loss, floaters, or a “dark curtain” coming down over your central and peripheral vision. 

Updated on  April 30, 2024
5 sources cited
Updated on  April 30, 2024
  1. Gupta et al. “Exudative retinitis (Coats disease).” National Library of Medicine, 2023.
  2. Kleonikos, A. “Coats disease.” American Academy of Ophthalmology, 2022.
  3. Coats disease.” National Organization for Rare Disorders, 2015. 
  4. Boyd, K. “Detached retina.” American Academy of Ophthalmology, 2022.
  5. Chay et al. “The many faces of Coats’ Disease.” Review of Ophthalmology, 2015.
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