Coats Disease: What It Is, Why It Happens, and How It's Treated
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 14, 2026
Quick Answer
Coats disease is a rare condition in which the tiny blood vessels in a child's retina develop incorrectly, swelling and leaking fluid [1] [5]. It usually affects one eye and is more common in boys [1] [3] [6]. Symptoms include worsening vision, crossed eyes and a white or silvery pupil [1] [3]. Early stages may only need monitoring; later stages need cryotherapy, anti-VEGF injections or surgery [1] [3].
What the research says
Coats disease mostly affects young boys, in one eye. In 150 consecutive patients, the median age at diagnosis was 5 years, 76% were male, and 95% had only one eye affected. (Shields et al., American Journal of Ophthalmology, 2001) [6].
Many children already have serious vision loss at diagnosis. In the same series, vision was 20/200 or worse in 76% of eyes at presentation, and 47% of eyes had a total retinal detachment. (Shields et al., American Journal of Ophthalmology, 2001) [6].
What Is Coats Disease?
Coats disease causes blood vessels in your child's eye to develop incorrectly. Specifically, it affects blood vessels in their retina. Eventually, it makes the blood vessels swell and leak plasma into their retina [1]. You might see it referred to as Coats' syndrome or exudative retinitis.
The retina is the layer at the very back of your eyeball. It converts light that enters your eye into electrical signals your optic nerve sends to your brain, which creates the images you see. Blood vessels are channels that carry blood throughout your body. They form a closed loop, like a circuit, that begins and ends at your heart.
Coats disease makes the tiny blood vessels in your child's retina dilate (expand), twist and leak [1]. The leak is usually small and takes time to cause symptoms you'll notice — think about the difference between running over a nail and making your car's tire lose air slowly and hitting a pothole and bursting it all at once.
Coats disease usually affects one eye (unilaterally), but it can develop in both eyes at the same time (bilateral Coats disease) [1] [3] [6]. It's usually diagnosed in kids and teens but can develop at any age. It can make your child's vision worse and lead to serious complications like a detached retina and blindness in their affected eye [1] [5].
Key Terms to Know
Term | What It Means |
|---|---|
Retina | The layer at the very back of your eyeball that converts light into electrical signals your brain turns into images |
Optic nerve | The nerve that carries signals from the retina to your brain |
Coats disease (exudative retinitis) | A condition where retinal blood vessels develop abnormally, swell, and leak fluid into the retina |
Plasma | The fluid part of blood that leaks into the retina in Coats disease |
Unilateral / bilateral | Affecting one eye / affecting both eyes at the same time |
Detached retina | When the retina separates from the back of the eye — a serious complication of Coats disease |
Cryotherapy | A treatment that applies extreme cold to freeze and destroy abnormal tissue |
Anti-VEGF drugs | Medication injected into the retina to stop blood vessels from leaking |
What Are the Symptoms of Coats Disease?
Your child might not have any symptoms of Coats disease, especially early on. If they do have symptoms, they might include worsening vision, crossed eyes (strabismus), eye pain, and a white or silvery pupil (leukocoria) [1] [3].
Symptom | What You Might Notice |
|---|---|
Worsening vision | Your child's eyesight gradually gets worse in the affected eye |
Crossed eyes (strabismus) | One eye appears turned inward or outward instead of lined up with the other |
Eye pain | Your child complains of pain in the affected eye |
White or silvery pupil (leukocoria) | The pupil, normally dark, looks white or silvery |
Because symptoms often don't appear until leaking has been going on for some time, watching for any changes in your child's eyes or vision is important.
What Are the Stages of Coats Disease?
Coats disease progresses, or becomes more severe, in a series of defined stages. They range from stage 1 (the mildest) to stage 5 (most severe) [1] [4]:
Stage | What Happens |
|---|---|
Stage 1 | Your eye care specialist notices abnormal blood vessels, but they're not causing any issues or symptoms |
Stage 2 | The affected blood vessels start leaking — this will probably affect your child's vision |
Stage 3 | The Coats disease causes a detached retina in the affected eye |
Stage 4 | The condition causes glaucoma in your child's eye |
Stage 5 | Sometimes called end-stage Coats disease — it causes blindness in the affected eye |
What Causes Coats Disease?
Experts aren't sure what causes Coats disease. It usually happens without a specific cause (idiopathically) [1] [4].
Coats disease isn't a genetic disorder. This means it's not passed through generations of a family — it's not hereditary [1] [5].
Who Is at Risk?
Anyone can develop Coats disease. But boys are three times more likely to have it than girls [1] [2] [5].
Coats disease can develop at any age. Providers usually diagnose kids and teens before they're 16 [1]. It's rare, but babies can be born with Coats disease, and it can develop in some infants. Around one-third of people with Coats disease are adults older than 30 [1] [5].
Risk Factor | Detail |
|---|---|
Sex | Boys are three times more likely to have it than girls |
Age | Usually diagnosed in kids and teens before 16; can develop at any age, including in babies and in adults over 30 (about one-third of cases) |
Genetics | None — it's not genetic or hereditary and happens randomly |
How Is Coats Disease Diagnosed?
An eye care specialist will diagnose Coats disease with an eye exam. They'll look at your child's eyes (including inside them) and examine your child's eyes and vision with a visual acuity test [1].
Imaging Test | What It Does |
|---|---|
Optical coherence tomography (OCT) | A scan that takes detailed cross-section images of the retina |
Angiography | A test that images the blood vessels, often after a dye is used |
Ultrasound | Sound-wave imaging of the inside of the eye |
MRI | Magnetic resonance imaging of the eye and surrounding area |
CT scan | Computed tomography scan producing detailed cross-section images |
How Is Coats Disease Treated?
How Coats disease is treated depends on which stage your child has.
If an eye care specialist diagnoses them early (stage 1 or early in stage 2), your child may not need any treatment [1] [3]. Your eye care specialist will regularly check your child's eyes for changes in their retina's blood vessels.
If your child has more severe symptoms or is in a later stage, Coats disease treatments include:
Cryotherapy. Cryotherapy is a treatment where your healthcare provider applies extreme cold to freeze and destroy abnormal tissue. They'll freeze the affected blood vessels in your child's retina to prevent them from leaking anymore [1].
Medication. An ophthalmologist can inject anti-vascular endothelial growth factor (VEGF) drugs into your child's retina. This can stop their blood vessels from leaking and prevent a retinal detachment [1] [3].
Surgery. If your child has later-stage Coats disease or has experienced a detached retina, they'll need surgery to repair the damage [1] [5].
Treatment | How It Works | When It's Used |
|---|---|---|
Monitoring | Regular eye exams to watch for changes in the retina's blood vessels | Early disease (stage 1 or early stage 2) |
Cryotherapy | Extreme cold freezes and destroys the leaking abnormal blood vessels | More severe symptoms or later stages |
Medication (anti-VEGF injection) | An ophthalmologist injects anti-VEGF drugs into the retina to stop leaking and prevent retinal detachment | More severe symptoms or later stages |
Surgery | Repairs damage or a detached retina | Later-stage disease or after a retinal detachment |
What Is the Outlook for Coats Disease?
How your child's eye and vision will be affected by Coats disease depends on what stage it was diagnosed at, and how well their eye responds to treatment. Studies have found that the older kids are when they develop Coats disease, the less likely it is that they have severe cases that progress to later stages [1] [2].
If Coats disease is diagnosed early in stages 1 or 2, there's a good chance your child won't have severe long-term effects [1]. However, they might have reduced or low vision in their affected eye, even after treatment [1] [3].
What Are the Complications?
While your child has Coats disease, they'll have an increased risk for other conditions that can affect their eye, including glaucoma, cataracts, uveitis, and neovascularization (developing new, abnormal blood vessels) [1] [5].
A Note on Catching It Early
Coats disease is a rare condition that affects the tiny blood vessels in your child's retina at the back of their eye. The best chance to lessen its impact on their eye and vision is to catch Coats disease in an early stage.
Can Coats Disease Be Prevented?
Because it happens randomly with no cause, there's nothing you can do to prevent Coats disease [1]. Visit your eye care specialist for follow-up eye exams to monitor any changes in your child's retina after they've been diagnosed.
Coats Disease vs. Retinoblastoma: What's the Difference?
Coats disease and retinoblastoma are both conditions that affect the retinas in kids' eyes.
Coats disease happens when a child's retinal blood vessels develop abnormally and leak fluid into their eye. Retinoblastoma is a rare type of cancer that grows on the retina [1]. If the tumor hasn't spread beyond the eye, most children with retinoblastoma live cancer-free after treatment [1].
Both conditions have similar symptoms, especially early on in their progression [1]. Visit your eye care specialist right away if you notice any symptoms or changes in your child's eyes.
When Should You See a Healthcare Provider?
See your healthcare provider or eye care specialist as soon as you notice any changes in your child's eyes or vision.
If your child has a sudden loss of vision, severe eye pain, or sees new flashes or floaters in their eyes, go to the emergency room right away [1].
Questions to Ask Your Provider
Questions you may want to ask your provider include: which stage of Coats disease does my child have? How often will they need follow-up exams? Will they need treatment? Which treatments will they need? How much will Coats disease affect their vision?
What is the bottom line on Coats disease?
Coats disease is a rare condition that makes the tiny blood vessels in a child's retina develop abnormally — dilating, twisting, and slowly leaking fluid into the retina. It usually affects one eye, strikes mostly kids and teens before age 16 (though it can appear at any age), and is three times more common in boys [1] [5]. It isn't genetic and has no known cause [1] [5]. It progresses through five stages, from silent abnormal vessels to retinal detachment, glaucoma, and blindness in the affected eye [1]. Symptoms — worsening vision, crossed eyes, eye pain, a white or silvery pupil — often arrive late, which is why regular eye exams matter. An eye care specialist diagnoses it with an eye exam and imaging tests. Early stages may only need monitoring; later stages are treated with cryotherapy, anti-VEGF injections, or surgery [1] [3]. The earlier it's caught, the better the outcome, though reduced vision in the affected eye is still possible. There's no way to prevent it, but catching it early gives your child the best chance of keeping their vision. See your provider right away for any changes in your child's eyes or vision — and go to the emergency room for sudden vision loss, severe eye pain, or new flashes or floaters.
Frequently Asked Questions
What is Coats disease?
Coats disease is a condition that causes blood vessels in your child's eye to develop incorrectly. It affects blood vessels in the retina, making them swell and leak plasma into the retina. It's also called Coats' syndrome or exudative retinitis.
What is the retina?
The retina is the layer at the very back of your eyeball. It converts light that enters your eye into electrical signals your optic nerve sends to your brain, which creates the images you see.
Why is Coats disease sometimes called exudative retinitis?
Because the condition makes the retina's blood vessels leak (exude) fluid into the retina. The terms describe the same condition.
Is Coats disease the same as a slow leak?
Sort of — the leak from the affected vessels is usually small and takes time to cause noticeable symptoms. Think of the difference between running over a nail and making your car's tire lose air slowly versus hitting a pothole and bursting it all at once.
Does Coats disease affect one eye or both?
It usually affects one eye (unilaterally), but it can develop in both eyes at the same time (bilateral Coats disease).
Who gets Coats disease?
Anyone can develop it. It's usually diagnosed in kids and teens, but it can develop at any age — including in babies and in adults over 30 (about one-third of people with Coats disease are adults older than 30).
Are boys or girls more likely to get Coats disease?
Boys are three times more likely to have it than girls.
What age is Coats disease usually diagnosed?
Providers usually diagnose kids and teens before they're 16. It's rare, but babies can be born with it, and it can develop in some infants.
Is Coats disease genetic?
No. Coats disease isn't a genetic disorder. It's not passed through generations of a family — it's not hereditary.
What causes Coats disease?
Experts aren't sure what causes it. It usually happens without a specific cause (idiopathically).
Can Coats disease be prevented?
No. Because it happens randomly with no cause, there's nothing you can do to prevent it. Regular follow-up eye exams help monitor the retina after diagnosis.
What are the symptoms of Coats disease?
Your child might not have any symptoms, especially early on. If symptoms do appear, they might include worsening vision, crossed eyes (strabismus), eye pain, and a white or silvery pupil (leukocoria).
What is leukocoria?
A white or silvery pupil — instead of the pupil looking dark as usual, it appears white or silvery.
What is strabismus?
Crossed eyes — when the eyes aren't lined up and one may appear turned inward or outward.
What are the stages of Coats disease?
Stages 1 through 5, from mildest to most severe: stage 1 (abnormal vessels without symptoms), stage 2 (leaking vessels that will probably affect vision), stage 3 (detached retina), stage 4 (glaucoma), and stage 5 (end-stage, causing blindness in the affected eye).
What happens at stage 1?
Your eye care specialist notices abnormal blood vessels in your child's eye, but they're not causing any issues or symptoms yet.
What happens at stage 2?
The affected blood vessels start leaking, which will probably affect your child's vision.
What happens at stage 3?
Coats disease causes a detached retina in the affected eye.
What happens at stage 4?
Coats disease causes glaucoma in your child's eye.
What happens at stage 5?
Stage 5 is sometimes called end-stage Coats disease. It causes blindness in the affected eye.
How is Coats disease diagnosed?
An eye care specialist diagnoses it with an eye exam, looking at your child's eyes (including inside them) and testing vision with a visual acuity test. Imaging tests such as OCT, angiography, ultrasound, MRI, or CT scan may also be needed.
What is a visual acuity test?
A test that examines how clearly your child can see — typically reading letters on an eye chart.
What imaging tests are used for Coats disease?
Optical coherence tomography (OCT), angiography, ultrasound, MRI (magnetic resonance imaging), and CT scan (computed tomography scan).
How is Coats disease treated?
Treatment depends on the stage. Early disease (stage 1 or early stage 2) may need no treatment, just regular monitoring. More severe or later-stage disease is treated with cryotherapy, anti-VEGF medication injections, or surgery.
What is cryotherapy for Coats disease?
A treatment where your healthcare provider applies extreme cold to freeze and destroy abnormal tissue. The affected blood vessels in the retina are frozen to prevent further leaking.
What are anti-VEGF drugs?
Medication an ophthalmologist injects into your child's retina to stop blood vessels from leaking and prevent a retinal detachment.
When is surgery needed?
If your child has later-stage Coats disease or has experienced a detached retina, surgery is needed to repair the damage.
What happens if Coats disease is caught early?
If diagnosed early in stages 1 or 2, there's a good chance your child won't have severe long-term effects. However, they might still have reduced or low vision in their affected eye, even after treatment.
What happens if Coats disease is caught late?
Later-stage Coats disease has a higher risk of blindness in the affected eye.
Does age affect how severe Coats disease gets?
Yes. Studies have found that the older kids are when they develop Coats disease, the less likely it is that they have severe cases that progress to later stages.
What complications can Coats disease cause?
Children with Coats disease have an increased risk of glaucoma, cataracts, uveitis, and neovascularization (developing new, abnormal blood vessels).
What is neovascularization?
The development of new, abnormal blood vessels in the eye.
What is the difference between Coats disease and retinoblastoma?
Coats disease happens when retinal blood vessels develop abnormally and leak fluid into the eye. Retinoblastoma is a rare type of cancer that grows on the retina. If the tumor hasn't spread beyond the eye, most children with retinoblastoma live cancer-free after treatment. Both conditions have similar symptoms early on.
How can I help my child after diagnosis?
Visit your eye care specialist for follow-up eye exams to monitor any changes in your child's retina. Watch closely for changes in their eyes or vision, and follow the treatment plan your provider recommends.
What questions should I ask my provider?
Consider asking: Which stage does my child have? How often will they need follow-up exams? Will they need treatment? Which treatments will they need? How much will Coats disease affect their vision?
When should I take my child to the emergency room?
Go to the emergency room if they have a sudden loss of vision, severe eye pain, or new flashes or floaters in their eyes.
What are flashes and floaters?
Flashes are brief streaks of light, and floaters are spots or strands that drift across your vision. New flashes or floaters can signal a serious eye problem like a retinal detachment.
When should I see a healthcare provider for my child?
See your healthcare provider or eye care specialist as soon as you notice any changes in your child's eyes or vision. The best chance to lessen the impact on their eye and vision is to catch Coats disease in an early stage.
Related Reading
References
Cleveland Clinic. Coats Disease. Cleveland Clinic. Last updated July 3, 2024. https://my.clevelandclinic.org/health/diseases/coats-disease
American Academy of Ophthalmology. Coats Disease. EyeWiki. Accessed October 30, 2026. https://eyewiki.aao.org/Coats_Disease
American Association for Pediatric Ophthalmology and Strabismus. Coats' Disease. AAPOS. Updated October 2024. https://www.aapos.org/glossary/coats-disease
Gupta A, Paulbuddhe VS, Shukla UV, Tripathy K. Exudative Retinitis (Coats Disease). StatPearls (NCBI Bookshelf). Last update August 25, 2023. PMID 32809517. https://www.ncbi.nlm.nih.gov/books/NBK560682/
National Organization for Rare Disorders. Coats Disease. NORD (National Organization for Rare Disorders). Last updated July 10, 2015. https://rarediseases.org/rare-diseases/coats-disease/
Shields JA, Shields CL, Honavar SG, Demirci H. Clinical variations and complications of Coats disease in 150 cases: the 2000 Sanford Gifford Memorial Lecture. Am J Ophthalmol. 2001;131(5):561-571. PMID 11336930. https://doi.org/10.1016/s0002-9394(00)00883-7
Medical disclaimer
This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read here. Individual treatment decisions should always be made with your healthcare team, ideally including a qualified eye care specialist. If your child has sudden vision loss, severe eye pain, or new flashes or floaters, seek emergency care right away.
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