Coats disease is a rare eye condition in which the blood vessels of the retina develop abnormally, becoming widened and leaky. That leakage allows fluid and fatty deposits to accumulate under and within the retina, progressively threatening vision. First described by the British ophthalmologist George Coats in 1908, the disease overwhelmingly strikes one eye in young boys, with most cases diagnosed before age ten. It is not inherited in the traditional sense and has no known connection to broader health conditions, yet its resemblance to a deadly childhood eye cancer makes accurate diagnosis critical.
Who Gets Coats Disease and How It Appears
The classic patient is a boy under ten with vision trouble in one eye. A large study of 98 children found the average age at diagnosis was about five and a half years, and children younger than four were more likely to present with a white pupil reflex (leukocoria) or a crossed eye (strabismus) rather than complaints about blurry vision.1Retina. Younger Age at Presentation in Children with Coats Disease Is Associated with More Advanced Stage and Worse Visual Prognosis That white glow in the pupil, often noticed in photographs or by a parent catching light reflecting off the child’s eye, is frequently the first clue. Older children and teens are more likely to notice their vision slipping in one eye before anyone else detects a visible sign.
Boys account for the vast majority of cases, and both eyes are involved only rarely. The disease appears across all ethnic groups without significant disparities.2PubMed Central. Coats disease: An overview of classification, management and outcomes Because it is sporadic, meaning it arises spontaneously rather than running in families, parents of an affected child are not at elevated risk of having another child with the disease.
What Goes Wrong Inside the Eye
The core problem is the retinal blood vessels themselves. In a healthy eye, retinal capillaries form a tight, well-organized network that delivers oxygen without leaking. In Coats disease, segments of these vessels balloon out into what clinicians call telangiectasias, tiny dilated pouches and channels that no longer hold fluid properly. Lipid-rich fluid seeps through the vessel walls and collects between and beneath the layers of the retina. Over time that yellowish, cholesterol-laden exudate can pile up enough to push the retina away from the underlying tissue, causing what is known as an exudative retinal detachment.
Researchers have found that a protein called norrin, which plays a role in normal blood vessel development in the retina, may be deficient in affected eyes. In a study of nine eyes that had been surgically removed from boys with Coats disease, one showed a somatic mutation in the NDP gene, the gene responsible for producing norrin, that was present only in retinal tissue, not elsewhere in the body.3PubMed. Coats’ disease of the retina (unilateral retinal telangiectasis) caused by somatic mutation in the NDP gene: a role for norrin in retinal angiogenesis That finding helps explain why the disease hits just one eye and does not show up in standard genetic testing of a blood sample: the mutation may arise only in a small patch of retinal cells during fetal development.
Beyond the structural vessel defect, the chemical environment inside a Coats eye is abnormal. Studies of the fluid inside affected eyes show elevated levels of signaling molecules tied to blood vessel growth and inflammation, including VEGF, IL-6, IL-8, and several others. The concentrations of some of these molecules track with disease severity: higher VEGF, IL-8, and related molecules correspond to more advanced stages.4PubMed Central. Aqueous humour cytokines profiles in eyes with Coats disease and the association with the severity of the disease This biochemical picture has practical consequences for treatment, which increasingly aims to block these molecular drivers of leakage and abnormal vessel growth.
The Retinoblastoma Question
Perhaps the most anxiety-inducing aspect of Coats disease is that it can look alarmingly like retinoblastoma, a malignant eye cancer that also tends to appear in young children and often presents with the same white pupil reflex. Distinguishing the two is not optional: retinoblastoma can be fatal if left untreated, while Coats disease, though potentially blinding, is not cancerous and never spreads beyond the eye. A comprehensive workup is essential to rule out retinoblastoma before settling on a Coats diagnosis.5Journal of Neonatal Surgery. Coats’ Disease Masquerading as Retinoblastoma: Diagnostic Dilemmas
MRI has become a key tool in making this distinction. Retinoblastoma tends to show up with features like a larger eye, visible seeding of tumor cells in the vitreous jelly, and a characteristic sharp V-shaped pattern of retinal detachment. Coats disease, by contrast, is more likely to feature a normal or smaller eye, the absence of calcifications, and certain distinctive findings such as intraretinal macrocysts and enhancing nodules beneath the fovea.6PubMed Central. MR Imaging Features to Differentiate Retinoblastoma from Coats’ Disease and Persistent Fetal Vasculature Even with these clues, the overlap is real enough that some children undergo examination under anesthesia, ultrasound, and sometimes repeated imaging before a confident diagnosis is reached.
How Coats Disease Is Diagnosed and Monitored
Once retinoblastoma has been excluded, ophthalmologists rely on a set of imaging tools to map the disease and guide treatment. Fluorescein angiography, in which a fluorescent dye is injected into a vein and photographed as it travels through the retinal vessels, remains the gold standard for visualizing the hallmark findings: telangiectasias, “light bulb” shaped microaneurysms, areas where capillaries have dropped out entirely, and zones where dye leaks freely through damaged vessel walls.7PubMed Central. Ultra-Widefield Fluorescein Angiographic Features Influencing Visual Prognosis in Coats Disease Ultra-widefield versions of this test can capture the far periphery of the retina, where many of the abnormal vessels hide.
Optical coherence tomography (OCT) provides cross-sectional images of the retinal layers, revealing the fluid pockets, fatty deposits, and structural disruption caused by the disease. One study of 27 eyes found that about two-thirds had visible fatty deposits within the retina, over half showed disruption of a critical photoreceptor layer, and roughly a quarter had a distinctive nodule beneath the fovea, the central vision zone. Nearly all of these structural changes correlated with worse visual acuity.8PubMed Central. Spectral domain optical coherence tomography findings in Coats’ disease Newer angiographic versions of OCT can map blood flow without any dye injection, revealing abnormal vascular patterns and areas of poor circulation in the deeper retinal and choroidal layers.9American Journal of Ophthalmology Case Reports. Optical coherence tomography angiography and multimodal imaging in the management of Coats’ disease
Interestingly, even the seemingly unaffected fellow eye may not be entirely normal. One study using ultra-widefield angiography found that about a third of fellow eyes in children with Coats disease showed areas of peripheral capillary non-perfusion, suggesting the vascular abnormality may be subtler and more widespread than the classic “one-eye disease” label implies.10PubMed. Comparison of retinal vascular abnormalities in the fellow eyes of children with Coats’ disease and normal subjects using ultra-widefield fundus fluorescein angiography
Treatment Strategies
There is no pill or single procedure that cures Coats disease. Treatment aims to shut down the leaky vessels, reduce fluid buildup, and prevent the retina from detaching further. The approach depends heavily on how advanced the disease is at diagnosis.
For early and moderate stages, where the retina is still attached or only partially detached, the mainstay treatments are laser photocoagulation and cryotherapy. Laser directs focused heat onto the abnormal vessels to seal them shut, while cryotherapy uses a freezing probe applied to the outside of the eye to destroy the same targets. A pooled analysis of treatment outcomes found that laser was protective against the development of scar tissue on the retina’s surface, whereas cryotherapy carried a somewhat higher risk of tractional retinal detachment, where scar tissue pulls the retina out of position.11PubMed Central. Treatment of Coats’ disease: an analysis of pooled results Long-term follow-up data reinforce that catching the disease early makes a meaningful difference: eyes treated at an earlier stage maintained good vision for about three decades afterward, while those treated at a stage where the central retina was already involved did not regain sharp vision but also did not progress to the most advanced, destructive stages.12PubMed Central. Coats’ Disease: Very Long-Term Outcome After Early Stage Conventional Treatment
Anti-VEGF injections, delivered directly into the eye, have become an important addition to the toolkit, particularly for more advanced disease. By blocking the signaling molecule that drives both vessel leakage and new abnormal vessel growth, these drugs can shrink exudation and flatten subretinal fluid. One study showed resolution of fluid and regression of abnormal vessels in all pediatric patients treated with bevacizumab, though the adult patients in the same series did not see a statistically significant improvement in vision.13PubMed. The effect of intravitreal bevacizumab injection as the initial treatment for Coats’ disease A cautionary note applies here: anti-VEGF drugs can occasionally promote the formation of fibrous scar tissue, which can tug on the retina. One small series reported tractional retinal folds in three of four eyes that received bevacizumab alongside other interventions.14PubMed Central. Risk of Tractional Retinal Detachment Following Intravitreal Bevacizumab Along with Subretinal Fluid Drainage and Cryotherapy for Stage 3B Coats’ Disease The risk appears higher when the drug is used in eyes with large amounts of subretinal fluid, so close monitoring and sometimes staged treatment are needed.
In advanced cases, where the retina has ballooned away from the back of the eye with a large pocket of fluid underneath, surgical drainage of that fluid becomes necessary. Surgeons have developed minimally invasive techniques to drain the subretinal fluid through the wall of the eye, then apply laser or cryotherapy to the exposed abnormal vessels, often finishing with an anti-VEGF injection. One series using a small-gauge trocar system for drainage found that the retina reattached in all treated patients, and severe complications such as tears in the retina or bleeding were not observed.15PubMed Central. Novel transscleral sutureless subretinal fluid drainage using a 25-gauge trocar-cannula with a self-closing valve in patients with advanced Coats disease Draining the fluid also physically removes a reservoir of VEGF and inflammatory molecules, which may contribute to better outcomes than leaving that fluid in place.16Scientific Reports. Vitrectomy and external drainage of subretinal fluid containing high concentration of vascular endothelial growth factor for advanced Coats disease
When the Disease Threatens the Eye Itself
Left untreated or diagnosed very late, Coats disease can escalate beyond vision loss to threaten the eye itself. One of the most feared complications is neovascular glaucoma, in which the chronic oxygen deprivation caused by all that vascular dysfunction triggers new, fragile blood vessels to grow on the iris and clog the eye’s drainage angle. This drives eye pressure dangerously high and causes severe pain. Historically, eyes that reached this point were often surgically removed to relieve the pain. More recently, a combination of anti-VEGF injections and glaucoma drainage devices has allowed some of these eyes to be saved.17American Journal of Ophthalmology Case Reports. Coats disease presenting with vitreous hemorrhage and neovascular glaucoma
A long-term study of children with Coats disease identified several features that predicted poor outcomes for keeping the eye: extensive scar tissue on the retina surface, bleeding into the vitreous, tractional or combined retinal detachment, and cataracts. Advanced stage at presentation, specifically stage 3B and above, was the strongest predictor of eventually losing the eye. The overall rate of keeping the eye in that series was about 92%, reflecting the reality that most children treated in time can retain the globe even if central vision is compromised.18PubMed Central. Coats’ disease – Prognostic factors for globe and vision salvage in children, a long-term experience
Adult-Onset Coats Disease
While the textbook case is a young boy, Coats disease can show up for the first time in adults past age 30. These adult-onset cases are considered rare and behave differently from the childhood form in several ways.19PubMed. Adult-onset Coats disease Adults tend to present with unilateral vision loss, but the disease progresses more slowly and the fatty deposits tend to be more localized rather than spreading across the retina. Complications like retinal detachment and neovascular glaucoma, while possible, are comparatively less common in adults.20PubMed Central. A Brief Review on Adult-Onset Coats’ Disease
The biochemical profile also differs. Studies comparing the fluid inside the eyes of pediatric and adult patients found significantly lower VEGF levels in adults, while inflammatory markers like IL-6 played a more prominent role.21Investigative Ophthalmology & Visual Science. Differences in Aqueous Concentrations of Cytokines in Pediatric and Adult patients with Coats’ disease This has practical implications for treatment: a standard anti-VEGF injection might be the right first move in a child’s eye flooded with VEGF, but an adult with low VEGF and high inflammation might respond better to an anti-inflammatory implant. One case series demonstrated exactly this: adults with macular swelling that did not respond to anti-VEGF therapy showed improvement after switching to a steroid implant, guided by actual measurement of the molecular levels in their eye fluid.22PubMed Central. Levels of cytokines in the aqueous humor guided treatment of refractory macular edema in adult-onset Coats’ disease
Coats-Like Syndromes Linked to Other Conditions
True Coats disease is isolated: it affects the eye and nothing else. But a handful of systemic conditions can produce retinal findings that look very similar, and these are typically called Coats-like retinopathy rather than Coats disease proper. The most well-known association is with facioscapulohumeral muscular dystrophy (FSHD), a genetic muscle disease. Retinal telangiectasias resembling those in Coats disease have been found in a substantial percentage of FSHD patients when screened with angiography.23PubMed. Coats-like retinopathy in an infant with preclinical facioscapulohumeral dystrophy Most of these patients have no eye symptoms and the vascular changes are caught only on screening, but in rare instances, including in infants who have not yet shown muscle weakness, the eye findings can be severe enough to mimic full-blown Coats disease.
Other conditions, including certain mutations affecting telomere maintenance, have also been linked to Coats-like retinal changes, though the underlying mechanisms and clinical presentations are distinct from classic Coats disease.24PubMed Central. Coats syndrome in facioscapulohumeral dystrophy type 1 The distinction matters because a child diagnosed with what appears to be Coats disease but who also has bilateral involvement or subtle systemic symptoms might warrant genetic testing for an underlying condition that changes the monitoring and management plan.
Protecting Vision Beyond Treating the Disease
Even after the leaky vessels are sealed and the fluid has been absorbed, children with Coats disease face ongoing vision challenges that standard retina-focused treatment does not address. Because the disease typically affects just one eye, the brain can start to favor the healthy eye and suppress input from the weaker one, a process known as amblyopia. Without intervention, that “lazy eye” effect compounds the damage already done by the disease itself.
A recent study found that glasses for correctable refractive errors or for protecting the good eye were prescribed to only half the children in the cohort. Children who saw a pediatric eye specialist in addition to a retina specialist were far more likely to receive glasses and amblyopia treatment. Among those treated for amblyopia with patching and spectacles, some showed measurable improvement in visual acuity.25PubMed Central. Preventable vision loss in children with Coats disease The takeaway is straightforward: managing Coats disease is not only about stopping leakage and preventing detachment. Children also benefit from routine vision correction, amblyopia screening, and protection of the unaffected eye, and these needs are easy to overlook when the focus is on retinal surgery.