What is Coats disease?
Eye doctors can usually diagnose Coats disease during a routine eye exam.
Coats disease is a rare condition in which abnormal blood vessels in the retina dilate and leak fluid, resulting in damage to the retina and possibly vision loss. It most often appears at 8-10 years of age, affects males three times more often than females, and usually affects only one eye. The cause is unknown, and it does not appear to be hereditary.
The retina is the light-sensing layer of tissue in the back of the eye. In Coats disease, small retinal arteriole and capillary vessels become "telangiectatic," widening and dilating, forming small aneurysms that resemble tiny light bulbs. These vessels leak both fluid and fats, which build up in and under the retina. In advanced cases, the fluid accumulation is large enough to detach the retina (exudative retinal detachment). Large areas of retina may also lose proper blood supply, prompting the eye to produce new vessels (neovascularization). These neovascular vessels can result in additional problems such as glaucoma.
What are causes and risk factors for Coats disease?
Researchers have not identified causes for Coats disease. Researchers are exploring possible genetic abnormalities, such as a mutation of the Norrie disease protein (NDP) gene, as a possible cause of the disease. The condition occurs in males three times as often in females. There are no other known risk factors.
What are symptoms and signs of Coats disease?
The most common symptom is vision loss in one eye. Patients might also notice flashing lights and floaters in one eye. Vision loss can be gradual, and a child may not recognized the symptoms at first since the child may compensate well with the unaffected eye. Depth perception may decrease because the patient is relying on one eye for sight. Although the disease itself is painless, the development of markedly elevated pressure in the eye (glaucoma) late in the course of the disease can cause pain. The signs of Coats disease include the affected eye wandering, resulting in misaligned eyes (strabismus) and a white, gray, or pinkish reflection from the pupil (leukocoria), often seen in photographs taken with a flash.
Coats Disease Treatment
Cryotherapy is a pain treatment that uses a method of localized freezing temperatures to deaden an irritated nerve. Cryotherapy is also used as a method of treating localized areas of some cancers (called cryosurgery), such as prostate cancer and to treat abnormal skin cells by dermatologists. In this article we only discuss its use in nerve conditions.
In cryotherapy, a probe is inserted into the tissue next to the affected nerve. The temperature of the probe drops to then effectively freeze the nerve. The freezing inactivates the nerve and, as a result, painful nerve irritation is relieved. Cryotherapy is a relatively safe and effective means of treating localized nerve irritation.
How do health care professionals diagnose Coats disease?
Doctors usually diagnose Coats disease in children during a routine eye examination after examining the retina after pupil dilation. The abnormal telangiectatic blood vessels are visible, as are fluid and lipid (fat) deposits or retinal detachment. Ophthalmologists use additional imaging tools such as fluorescein angiography, optical coherence tomography (OCT) testing, and ultrasound to assess the extent of retinal involvement. In advanced cases, signs of glaucoma (such as increased eye pressure, abnormal neovascular vessels, and thinning [atrophy] of the optic nerve) may be present.
A thorough eye exam is essential not only to confirm the diagnosis of Coats disease but also to rule out other eye diseases that may resemble Coats. In particular, it is vital to rule out retinoblastoma, a rare but serious form of eye cancer that may appear at a very early age.
How do health care professionals determine the staging of Coats disease?
Carol Shields, MD, and Jerry Shields, MD, have divided Coats disease into five stages:
Stage 1: Retinal telangiectasias only
Stage 2: Telangiectasias and exudation: Stage 2 is further subcategorized depending on involvement of the fovea (center of the retina). 2A includes exudation not involving the fovea, and 2B, exudation involving the fovea.
Stage 3: Exudative retinal detachment similarly subcategorized into 3A and 3B based on foveal involvement
Stage 4: Total retinal detachment (RD) with glaucoma
Stage 5: End-stage disease with blindness
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What is the treatment for Coats disease?
Occasionally, the disease stops progressing on its own and may even spontaneously resolve. However, most cases require treatment aimed at halting the leakage from the telangiectatic blood vessels. A doctor may apply a freezing treatment (cryotherapy) or laser photocoagulation to the leaking vessels.
Some eyes respond well to treatment with steroids to control inflammation or drugs injected into the eye aimed at preventing growth of neovascular vessels. Surgery to repair a detached retina may be necessary, as well as treatment for glaucoma if it develops. In a small number of very advanced cases, if the eye is both blind and painful, or blind and deformed, a doctor may need to remove the eye and replace it with a prosthesis.
Is it possible to prevent Coats disease?
There is no known way to prevent Coats disease. However, it is possible to prevent or minimize the vision loss in many cases with proper treatment.
What is the prognosis of Coats disease?
The prognosis varies from mild cases that spontaneously resolve to advanced cases with blindness of the affected eye. In general, cases that appear at a younger age tend to be more severe than those that appear at a later age. The vision loss also largely depends on the involved portions of the retina. If fluid and lipid exudates build up in and around the fovea (center of the retina), the vision reduces significantly compared to eyes with exudates outside of the fovea. The presence of retinal detachment and neovascular vessels are associated with poor prognosis. However, in many cases, early and aggressive treatment can salvage vision. Only in cases in which the eye is either blind, painful, or disfiguring due to phthisis bulbi (shrinking of the eye in very advanced cases) would a doctor consider eye removal. If the eye is removed (enucleation), a prosthetic eye can be made to match the appearance of the other eye.
In all cases of Coats disease, it is wise to wear eye protection (shatterproof eyeglasses) to keep the other eye safe from accidental trauma.
Morris, B., B. Foot, and A. Mulvihill. "A Population-Based Study of Coats Disease in the United Kingdom I: Epidemiology and Clinical Features at Diagnosis." Eye 24 Dec. 2010: 1797-1801.
Shields, J.A., et al. "Classification and management of Coats disease: the 2000 Proctor Lecture." Am J Ophthalmol 131.5 May 2001: 572-83.