The clinical presentation of Coats disease varies widely. Typically, ophthalmoscopic examination reveals a localized area of subretinal exudates associated with vascular abnormalities. Vascular changes may include peripheral retinal telangiectasia, capillary and small-vessel dilatation and tortuosity, sheathing, capillary nonperfusion, and small aneurysms located at the equator of the eye and the ora serrata (most commonly, inferotemporal). The posterior pole is less frequently affected.
Exudation is a common feature that presents in most cases as flat intraretinal and subretinal exudates. These exudates initially appear in areas of telangiectasia and progress to become more widespread. Macular protein accumulation can occur directly from macular telangiectasia or indirectly from peripheral disease. A dense exudate or white nodule in the macula can progress to a disciform lesion that indicates a poor visual prognosis. Retinal hemorrhages may be seen. The vitreous remains clear until the advanced stages. Retinal cysts may be seen and are common in chronic retinal detachments of different etiologies.
The diagnosis may be suspected clinically by indirect ophthalmoscopic evaluation of both eyes, but ancillary testing is extremely helpful to differentiate Coats disease from retinoblastoma, which is a more feared disease. A high percentage of patients with this condition observed by primary care providers are referred to ophthalmologists specifically to rule out retinoblastoma.
A- and B-scan ultrasonography reveal low internal reflectivity consistent with an exudative retinal detachment and rules out the presence of a solid tumor. Intravenous fluorescein angiography helps to visualize the telangiectatic vessels as irregular dilated tortuous vessels filling in the late arterial and early venous phases. Microaneurysms are seen as "lightbulb aneurysms." Angiography reveals progressive leakage from abnormal vessels, adjacent areas of capillary dropout, and late staining of intraretinal exudates.[2,4]
On the basis of the clinical appearance and progression, Coats disease may be classified in five grades, as follows:
Grade I: Isolated focal exudates
Grade II: Massive elevated exudation
Grade III: Partial retinal detachment
Grade IV: Total retinal detachment
Grade V: Secondary complications
A more recent classification system has emerged, which is based on the prognosis. It grades the disease in the following manner:
Grade I: Telangiectasias only
Grade II: Telangiectasias and exudation
Grade III: Exudative retinal detachment
Grade IV: Total retinal detachment with secondary glaucoma
Grade V: End-stage disease
Spiral CT has been used to rule out intraocular calcifications that more commonly present in retinoblastoma. The clinician must consider and rule out the possibility of retinoblastoma because, if left untreated, it can be fatal. As a result of concerns about radiation exposure, CT is less frequently used today for diagnosing intraocular pediatric tumors. MRI with gadolinium enhancement is helpful in evaluating the optic nerve and the globe. It is not, however, as valuable as CT or ultrasonography for detecting the intraocular calcium deposits commonly found in association with retinoblastoma tumors.
MRI is also very helpful for evaluating the pineal gland in cases of familial retinoblastoma. Subretinal fluid appears hyperintense on T1- and T2-weighted images. Solid tumors are hyperintense on T1-weighted images but hypointense in T2-weighted images.
The differential diagnosis of Coats disease is similar to that of leukocoria (which is extensive). It includes retinoblastoma; persistent fetal vasculature; retinopathy of prematurity; rhegmatogenous, exudative, or tractional retinal detachment; ocular toxocariasis, familial exudative vitreoretinopathy; retinal capillary hemangiomatosis (von Hippel-Lindau disease); cataract; glaucoma; uveitis; vitreous hemorrhage; and colobomas of the choroid and optic disc. Leber miliary aneurysm disease is an early or nonprogressive form of Coats disease.[2,4]
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Cite this: Mauricio E. Pons, Maria Silvana Horenstein. A 'Gleam' in the Left Eye of a 5-Year-Old Boy - Medscape - Jul 22, 2016.