Bilateral Fluorescein Angiographic Findings in Unilateral Coats’ Disease

Introduction

Coats’ disease is an idiopathic condition characterized by retinal telangiectasia, exudation, and exudative retinal detachment.^1,2 One of the mysteries of this condition is its unilateral nature. Using dilated fundus examinations, previous studies have demonstrated that Coats’ disease affects only one eye in 80% to 95% of cases.^3,4 However, no study describes peripheral fluorescein angiography findings in the contralateral retina of patients with unilateral Coats’ disease. It is therefore possible that bilateral peripheral vascular changes exist that are unrecognized by a standard diagnostic work-up. We describe two patients with clinically unilateral Coats’ disease and peripheral vascular abnormalities by fluorescein angiography in their contralateral eye.

Case Reports

Case 1

A 4-year-old boy was referred to Bascom Palmer Eye Institute for evaluation of retinal exudation in his right eye that was noted during a routine optometry visit. The patient denied an ocular history or family history of eye disease. On examination, the best-corrected visual acuity was 20/30 in the right eye and 20/100 in the left eye. Anterior segment examination was normal. Dilated fundus examination was normal in the right eye, but demonstrated exudation in the macula and peripheral retina of the left eye (Fig. 1). Dilated, aneurysmal vessels and telangiectasias were also noted in the peripheral retina of the left eye. The patient was diagnosed as having unilateral Coats’ disease and subsequently underwent an examination under anesthesia with fluorescein angiography by Retcam (Clarity Medical Systems, Pleasanton, CA). In the left eye, the fluorescein angiography demonstrated 360° of peripheral avascular retina, bordered posteriorly by leaking, telangiectatic retinal vascular abnormalities (Fig. 2). In the right eye, the fluorescein angiography was remarkable for peripheral avascular retina demarcated posteriorly by retinal vessels that appeared to run parallel to the ora serrata. These vessels did not leak or demonstrate aneurysmal dilation.

Figure 1. Unilateral Coats’ Disease with Macular Exudate and Superotemporal Retinal Telangiectasias in the Left Eye.

Figure 2. Montage Fluorescein Angiogram Images. (Left) Fluorescein Angiogram of the Right Eye Demonstrating Peripheral Avascular Retina Bordered Posteriorly by Vessels Running Parallel to the Ora Serrata (arrows). (Right) Peripheral Avascular Retina Bordered Posteriorly by Leaking Telangiectasias in the Left Eye.

Case 2

A 10-year-old boy was referred to Bascom Palmer Eye Institute for evaluation of retinal exudation in his left eye that was noted during a routine optometry visit. The patient denied an ocular history or family history of eye disease. On examination, the best-corrected visual acuity was 20/20 in both eyes. Anterior segment examination was normal. Dilated fundus examination demonstrated exudation in the superotemporal macula and peripheral retina of the right eye (Fig. 3). Retinal examination of the left eye was normal. The patient was diagnosed as having Coats’ disease in his right eye and subsequently underwent an examination under anesthesia with fluorescein angiography by Retcam. In the right eye, the fluorescein angiography highlighted focal areas of avascular retina surrounded by leaking, telangiectatic vessels in the superotemporal periphery (Fig. 4). Both eyes demonstrated areas of avascular retina in the far-periphery demarcated posteriorly by retinal vessels that appeared to run parallel to the ora serrata. These vessels did not leak or demonstrate aneurysmal dilation in the left eye.

Figure 3. Unilateral Coats’ Disease with Macular Exudate and Superotemporal Retinal Telangiectasias in the Right Eye.

Figure 4. (Top) Fluorescein Angiogram of the Right Eye Demonstrating Focal Areas of Avascular Retina Bordered by Leaking Telangiectasias. Peripheral Retina Is Avascular and Bordered Posteriorly with Loops of Vessels Running Parallel to the Ora Serrata. (Bottom) The Left Eye also Demonstrates Peripheral Avascular Retina Bordered Posteriorly by Vessels Running Parallel to the Ora Serrata (arrows).

Discussion

We present two patients with unilateral Coats’ disease diagnosed by clinical examination who demonstrate abnormal peripheral retinal vasculature in their contralateral eye on fluorescein angiography. In both patients, peripheral retinal vasculature in the contralateral eye is noted to turn parallel to the ora serrata, with avascular retina located anteriorly. This phenomenon may represent a previously unrecognized bilateral component of Coats’ disease. Furthermore, its phenotypic similarity to forms of familial exudative vitreoretinopathy may support arguments that these conditions exist on a continuous spectrum of congenital retinal vascular disorders.^5,6 Further study is required to determine the frequency of these vascular changes in patients with clinically unilateral disease. The results of this research could change our understanding of Coats’ disease and lead to novel genetic explanations for its occurrence.