Coats disease

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Coats’ disease, (also known as exudative retinitis or retinal telangiectasis, sometimes spelled Coates' disease), is a rare eye disorder, causing full or partial blindness, characterized by abnormal development of blood vessels behind the retina. Coats’ usually affects only one eye (unilateral) and occurs predominantly in young males, with the onset of symptoms generally appearing in the first decade of life. The specific cause of Coats’ disease remains unknown. Current research suggests a genetic component contributes to the disease. It is believed one is born with this disease, but Coats’ is not hereditary.

Coats’ disease results in a gradual loss of vision. Blood leaks from the abnormal vessels into the back of the eye, leaving behind cholesterol deposits and damaging the retina. Coats’ normally progresses slowly. At advanced stages, retinal detachment is likely to occur. Glaucoma, atrophy, and cataracts can also develop secondary to Coats’ disease. In some cases, removal of the eye may be necessary (enucleation).

Symptoms

Symptoms begin as blurred vision, usually pronounced when one eye is closed (due to the unilateral nature of the disease). Often the unaffected eye will compensate for the loss of vision in the other eye; however, this results in some loss of depth perception and parallax. Deterioration of sight may begin in either the central or peripheral vision. Deterioration is likely to begin in the upper part of the vision field as this corresponds with the bottom of the eye where blood usually pools. Flashes of light, known as photopsia, and floaters are common symptoms. Persistent color patterns may also be perceived in the affected eye. Initially, these may be mistaken for psychological hallucinations, but are actually the result of both retinal detachment and foreign fluids mechanically interacting with the photoreceptors located on the retina.

One early warning sign of Coats’ disease is yellow-eye in flash photography. Just as the red-eye effect is caused by a reflection off blood vessels in the back of a normal eye, an eye affected by Coats’ will glow yellow in photographs as light reflects off cholesterol deposits. Children with yellow-eye in photographs are typically advised to immediately seek evaluation from an ophthalmologist.

Coats’ disease itself is not painful. Pain may develop as a result of retinal detachment. Pain may also occur if fluid is not able to properly drain from the eye, causing the internal pressure to swell.

Differentiating Coats disease from other ocular lesions

Disease	Prominent clinical feature	Radiological findings
	Diagnosis made usually between 8-16 years (rarely in adulthood) Wide range of symptoms from being asymptomatic to decreased vision and strabismus. Decreased visual acuity at initial presentation has a poor prognosis.	Fundus examination reveals vascular lesions and exudates. Fluorescein angiography is the best method to visualize the lesions. CT and MRI are reserved for atypical cases.
Retinal detachment	Most common presenting symptoms are photophobia and floaters Visual field defects (described as curtain falling from periphery to the center)	Ophthalmoscope is not reliable in detecting retinal detachment as there might be associated hemorrhage Ultrasound can be used to identify and localize the detachment.
Hyperthyroid Ophthalmopathy	The hallmark is Eye protrusion, photophobia, lacrimation and later in the disease, diminished eye motility.	Ultrasonography: inflamed thickened extraocular muscles. CT: shows inflamed muscle and free tendon from inflammation MRI: shows periorbital fat expansion, increased water content of the muscles as a result of the inflammation.
Retinoblastoma	The most prominent sign is leukocoria, followed by strabismus The patient also may present with buphthalmos, corneal clouding and eye tearing.	Ultrasound: can detect the tumor as a result of the calcifications inside. MRI: assess sellar and parasellar regions .. it can also detect extraocular spread of the tumor.

Coats’ disease must be differentiated from retinoblastoma, Norrie disease, and Retinopathy of prematurity (ROP).
For more information on differential diagnosis of Coats’ disease please click here

MRI of the orbit showing Coats disease - Case courtesy of Dr Michael Sargent, https://radiopaedia.org/. From the case https://radiopaedia.org/cases/6089	MRI of the orbit showing retinal detachment - Case courtesy of A.Prof Frank Gaillard, https://radiopaedia.org/. From the case https://radiopaedia.org/cases/3134	MRI of the orbit showing retinoblastoma - Case courtesy of https://radiopaedia.org/. From the case https://radiopaedia.org/cases/11877	CT head showing hyperthyroid-induced orbitopathy - Case courtesy of A.Prof Frank Gaillard, https://radiopaedia.org/. From the case https://radiopaedia.org/cases/4854

Treatment

In the early stages, there are a few treatment options. Laser surgery or cryotherapy (freezing) can be used to destroy the abnormal blood vessels, thus halting progression of the disease. However, if the leaking blood vessels are clustered around the optic nerve, this treatment is not recommended as accidental damage to the nerve itself can result in permanent blindness. Coats’ disease may stop progressing all on its own, either temporarily or permanently. Cases have been documented in which the condition even reverses itself. However, once total retinal detachment occurs, sight loss is permanent in most cases. Removal of the eye (enucleation) is an option if pain or further complications arise.

External links

• http://www.orpha.net/data/patho/GB/uk-Coats.pdf
• http://www.coatsdisease.org/
• http://www.coatsdisease.net/
• http://www.revoptom.com/handbook/41.htm
• Personal story of Coates Disease