Bibliography

1.What is Coats disease?

Exudation, retinal telangiectasia, and retinal aneurysms are hallmarks of the disorder, named for the British ophthalmologist George Coats, who first described this condition in 1908. It comes on

painlessly and may be slow and insidious in its development. In many instances, Coats disease is not discovered until the patient is beyond childhood.

2.List the clinical characteristics of Coats disease.

•It is a lifetime disease.

•It occurs 80% to 90% of the time in young boys.

•It is usually unilateral.

•It is not familial.

•Characteristic retinal vascular lesions are telangiectatic-like “light bulb” aneurysms that are associated with capillary dropout in the fundus periphery (Fig. 41-1, B and D ).

•Intraretinal and subretinal exudation, a prominent feature, has a predilection to accumulate in the macular area (Fig. 41-1, A and C ); the exudate contains cholesterol crystals.

•Coats disease may lead to exudative retinal detachment, cataract, neovascular glaucoma, and phthisis bulbi.

3.What percentage of patients are girls?

Between 8% and 10% of patients are girls.

4.What is the most common age at which Coats disease becomes apparent?

Coats disease usually becomes apparent between 8 and 10 years of age. However, it can present in infancy and later in life. It is often much more severe when noted in infancy.

5.What percentage of cases are unilateral versus bilateral?

Approximately 80% to 90% of the cases are unilateral. When bilateral cases do develop, there is usually asymmetry, with one eye being much more involved than the other.

6.Are the retinal vascular changes easy to detect?

If the patient is cooperative, it is not hard to diagnose the peripheral retinal vascular changes. However, examination under general anesthesia may be necessary in younger patients.

7.How does this condition differ from Leber’s miliary aneurysms?

In 1912, Leber described retinal miliary aneurysms. He suggested that the conditions were one and the same as that reported by Coats, and that is the generally accepted thinking at the present time.

8.Do we know the etiology of Coats disease?

The precise etiology for Coats disease has not been determined.

9.Are there any conditions with which Coats disease can be confused?

When there is exudation in the macula and peripheral telangiectasia, and no retinal detachment, the Coats disease can be diagnosed with confidence. There are a number of conditions to rule out, most notably retinoblastoma, the malignant intraocular tumor that occurs in infancy and childhood. It has been estimated that approximately 3.9% of eyes originally diagnosed as harboring retinoblastoma were subsequently discovered to have Coats disease. See Table 41-1.

10.Can conditions other than retinoblastoma simulate Coats disease?

Angiomatosis retinae (von Hippel-Lindau syndrome), one of the phakomatoses, can cause exudation in the macula. This condition is inherited in an autosomal dominant fashion and has visceral and central nervous system hemangioblastomas as part of the syndrome. In addition, visceral cysts and tumors, including renal cell carcinoma, may occur. Early in its onset, the fundus picture is different from that of Coats disease in that angiomatosis retinae demonstrates a dilated and

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G

H I

J

Figure 41-1, cont’d  G, Exudate disappearing after laser treatment. H, Microaneurysmal changes in a patient with Coats disease. I, Histopathologic section of the retina in a patient with Coats disease with bullous retinal detachment almost touching the posterior lens capsule secondary. Aneurysmal changes can be seen in the nerve fiber layer. (Courtesy of Dr. Ralph Eagle.) J, Recurrent Coats in a 26-year-old male diagnosed at 5 years of age. Exudate is beginning to diminish 3 months after retreatment.

CHAPTER 41  COATS DISEASE  331

K

Figure 41-1, cont’d  K, 27-year-old male with retinitis pigmentosa and Coats disease. L, The patient in J has reduced and delayed hertz (hz) cone electroretinogram both eyes compatible with retinitis pigmentosa.

Table 41-1.  Differential Diagnosis of Coats Disease

1.Retinoblastoma

2.Familial exudative vitreoretinopathy

3.Von Hippel-Lindau disease

4.Retinopathy of prematurity

5.Persistent fetal vasculature

332  OPHTHALMOLOGY SECRETS IN COLOR

11.Other than fluorescein angiography, what may be helpful in confirming the diagnosis?

Ultrasonography and computed tomographic (CT) scans may help to differentiate between Coats disease and retinoblastoma by detecting the presence or absence of subretinal calcifications. Calcification is found in retinoblastoma, but it is extremely rare in Coats disease.

12.Is it advisable to obtain a computed tomographic scan?

CT scanning is perhaps the single most valuable test in diagnosing Coats disease because of its ability to delineate intraocular morphology, to qualify retinal densities, and to detect associated orbital or intracranial abnormalities. However, this does expose a young patient to low levels of radiation, especially if studies are repeated periodically.

13.Can aspiration of subretinal exudates aid in diagnosis?

The key diagnostic findings in the analysis of subretinal aspirates are the presence of cholesterol crystals and pigment-laden macrophages and the absence of tumor cells. This technique should be reserved for patients in whom retinoblastoma has been ruled out by all other noninvasive means, because tumor seeding may occur.

14.How is Coats disease managed?

If possible, it is desirable to treat the condition before exudate accumulates in the macular area. Treatment is directed at the peripheral vascular abnormalities. Photocoagulation can be used to eliminate these abnormal vessels. In patients with exudation under the peripheral vascular telangiectasia, cryotherapy may be preferable (Fig. 41-1, D). Elimination of the defective vessels prevents further leakage and is followed by resorption of the exudate over ensuing months. Because patients have been found to have elevated levels of vascular endothelial growth factor (VEGF), bevacizumab, triamcinolone, and dexamethasone have been injected intravitreally. Most of the time these drugs have been used as adjuvants to laser or cryotherapy. However, dramatic improvement has occasionally been reported when bevacizumab has been used as the primary mode of therapy. With the use of steroids, cataract has to be considered as a potential complication.

15.How long does it take for the exudate to disappear?

Resorption of the exudate may take up to a year or more before it is completely gone. Its disappearance becomes apparent in the first few months after treatment. Solid masses of exudate take on a more speckled appearance as the exudate goes away.

16.Is more than one treatment necessary?

If more than two quadrants have retinal telangiectasia, two or three treatments may be required.

17.Once the abnormal vessels are gone, is the patient considered cured?

Recurrence, which is usually heralded by the reappearance of exudate and is almost always associated with new vascular abnormalities, can occur even many years later. It is recommended that patients be scheduled for follow-up appointments at 6- to 12-month intervals throughout their lifetime. See Table 41-2.

18.Can this condition be managed once the retina has detached?

Vitreoretinal surgery may, in some cases, help to reattach the retina. At the time of surgery, it is necessary to treat the abnormal vessels by laser photocoagulation or cryotherapy. The vision in these eyes,

Table 41-2. Recurrence of Coats

Number of patients: 13

•Males: 11 (85%)

•Females: 2 (15%) Average follow-up: 12.4 years

•Range: 4 to 58 years

Average number of recurrences: 3.3

Oldest patient at time of recurrence: 58 years