Ophthalmology – Coats Disease

Basics

Description

Coats disease is an idiopathic retinal vascular disorder characterized by:

• Retinal telangiectasia
• Aneurysmal retinal vessels
• Breakdown of the blood-retinal barrier
• Massive intraretinal and subretinal lipid exudation
• Progressive exudative retinal detachment in advanced disease

Classic Coats disease is usually:

• Unilateral
• Sporadic
• Nonhereditary
• Seen predominantly in boys and young males
• Unassociated with systemic disease

The major pediatric diagnostic concern is:

Retinoblastoma, because both can present with leukocoria and retinal detachment.

Epidemiology

Most patients present during:

Childhood, often before age 10

but Coats disease can present:

• In adolescence
• In adulthood
• Rarely later in life

Adult-onset disease is often:

• More localized
• Less exudative
• More slowly progressive

than childhood disease.

Sex and Laterality

Typical epidemiologic pattern:

• Strong male predominance
• Unilateral in the great majority of cases

True bilateral classic Coats disease is extremely unusual.

Bilateral Coats-like retinopathy should prompt evaluation for:

• Inherited retinal vascular disorders
• Systemic syndromes
• Other causes of exudative retinopathy

Genetics

Classic Coats disease is generally:

Sporadic and nonhereditary

Somatic abnormalities involving the:

NDP signaling pathway

have been proposed in some cases, supporting a retinal vascular developmental mechanism.

Routine genetic testing is:

Not required for typical unilateral Coats disease.

When to Consider Genetic/Systemic Evaluation

Consider broader evaluation when there is:

• Bilateral retinal telangiectasia/exudation
• Neurologic abnormalities
• Growth abnormalities
• Skeletal or muscular disease
• Strong family history
• Atypical phenotype

Important Coats-like conditions include:

• Coats plus syndrome
• Familial exudative vitreoretinopathy
• Retinopathy of prematurity
• Incontinentia pigmenti
• Facioscapulohumeral muscular dystrophy-associated retinopathy
• Norrie disease-related retinopathy

Pathophysiology

The fundamental abnormality is:

Retinal vascular incompetence

with:

• Telangiectatic capillaries
• Aneurysmal dilatation
• Abnormal endothelial barrier
• Capillary nonperfusion

This leads to leakage of:

• Lipid
• Protein
• Fluid

into the retina and subretinal space.

Retinal Exudation

Chronic vascular leakage causes:

• Intraretinal hard exudates
• Macular exudation
• Subretinal exudation
• Exudative retinal detachment

Lipid accumulation may become extensive and yellow-white.

Retinal Ischemia

Areas of peripheral retinal nonperfusion may coexist with telangiectasia.

Ischemia contributes to:

• Progressive vascular abnormality
• VEGF production
• Rare neovascularization

Distribution

The abnormal vessels most commonly involve:

Temporal peripheral retina

but disease may extend:

• Inferiorly
• Superiorly
• Nasally
• Circumferentially

More extensive disease tends to occur in younger children.

Shields Classification

A commonly used staging system is:

Stage 1

Retinal telangiectasia only

No significant exudation.

Stage 2

Telangiectasia + exudation

Stage 2A

Exudation does not involve the fovea

Stage 2B

Exudation involves the fovea

This distinction is important because foveal involvement markedly worsens visual prognosis.

Stage 3

Telangiectasia + exudation + exudative retinal detachment

Stage 3A

Subtotal retinal detachment

Stage 3B

Total retinal detachment

Some classifications further divide stage 3A according to foveal involvement.

Stage 4

Total retinal detachment + secondary glaucoma

Usually represents advanced disease.

Stage 5

End-stage disease with:

• Blind eye
• Phthisis
• Severe chronic retinal detachment
• Sometimes chronic pain

Clinical Presentation

Typical presenting features include:

• Decreased vision
• Strabismus
• Leukocoria
• Abnormal red reflex
• Occasionally ocular pain in advanced disease

Some patients are discovered incidentally.

Leukocoria

Any child with:

Leukocoria or an abnormal red reflex

requires urgent ophthalmic evaluation.

Important causes include:

• Retinoblastoma
• Coats disease
• Persistent fetal vasculature
• Cataract
• Retinal detachment
• Toxocariasis

Strabismus

Strabismus may develop because of:

• Macular exudation
• Reduced visual acuity
• Sensory disruption

In young children, strabismus may be the first sign noted by parents.

Visual Loss

Reduced vision may result from:

• Foveal exudation
• Macular edema
• Subfoveal lipid
• Exudative retinal detachment
• Macular fibrosis
• Secondary amblyopia

Fundus Findings

Typical examination reveals:

• Telangiectatic retinal vessels
• Aneurysmal vascular dilatations
• Yellow intraretinal lipid exudation
• Peripheral capillary nonperfusion
• Exudative retinal detachment

Telangiectasia

Coats vessels may appear:

• Irregularly dilated
• Aneurysmal
• Light-bulb shaped
• Tortuous

They are often located in the:

Temporal peripheral retina

Hard Exudates

Lipid exudates may form:

• Circinate rings around abnormal vessels
• Dense macular deposits
• Extensive subretinal yellow material

Macular exudation is a major predictor of visual outcome.

Exudative Retinal Detachment

Progressive leakage may produce:

• Localized subretinal fluid
• Bullous subtotal detachment
• Total exudative retinal detachment

No retinal break is required.

Advanced Anterior Segment Findings

Advanced disease may cause:

• Iris neovascularization
• Secondary glaucoma
• Cataract
• Shallow anterior chamber
• Corneal edema

Chronic total retinal detachment may eventually produce:

Phthisis bulbi

Cholesterol Crystals

Advanced cases may occasionally demonstrate:

• Cholesterol crystals in the subretinal space
• Anterior chamber cholesterolosis

These reflect chronic lipid-rich exudation.

Diagnosis

Diagnosis is primarily:

Clinical + multimodal retinal imaging

The most important task is to:

Exclude retinoblastoma before undertaking treatment

in a child with leukocoria or exudative retinal detachment.

Examination Under Anesthesia

Young children may require:

Examination under anesthesia (EUA)

for complete:

• Dilated retinal examination
• Scleral depression
• Photography
• Fluorescein angiography
• Laser or cryotherapy

EUA is especially useful when office examination is incomplete.

Fundus Photography

Wide-field photography is valuable for:

• Baseline documentation
• Mapping telangiectasia
• Monitoring exudation
• Assessing treatment response

Fluorescein Angiography

Wide-field fluorescein angiography is one of the most useful tests in Coats disease.

It demonstrates:

• Telangiectatic vessels
• Aneurysms
• Peripheral nonperfusion
• Late leakage
• Previously occult abnormal vascular beds

FA helps define the area requiring:

Laser ablation.

Optical Coherence Tomography

OCT is particularly useful for macular assessment.

It may demonstrate:

• Intraretinal fluid
• Subretinal fluid
• Hard exudates
• Foveal distortion
• Epiretinal fibrosis

OCT is important for:

Visual prognosis and treatment monitoring.

OCT Angiography

OCTA may demonstrate:

• Abnormal superficial/deep vascular networks
• Capillary nonperfusion

but currently does not replace wide-field FA for mapping peripheral Coats vessels.

Ultrasonography

B-scan ultrasonography is especially important when:

• Dense exudation obscures the fundus
• Total retinal detachment is present
• Retinoblastoma is in the differential

Coats disease typically shows:

• Retinal detachment
• Subretinal exudation

without the classic intratumoral calcification of retinoblastoma.

Important Caveat About Calcification

Absence of calcification:

Does not by itself prove Coats disease

and the diagnosis of retinoblastoma should never be excluded on a single imaging feature.

The entire clinical and imaging picture must be considered.

Differential Diagnosis

The most important differential is:

Retinoblastoma

Other considerations include:

• Familial exudative vitreoretinopathy
• Persistent fetal vasculature
• Retinopathy of prematurity
• Retinal hemangioblastoma
• Retinal vasoproliferative tumor
• Toxocariasis
• Norrie disease
• Incontinentia pigmenti
• Retinal detachment of another cause
• Radiation retinopathy
• Severe retinal vasculitis

Coats Disease vs Retinoblastoma

Coats Disease

Typically:

• Male child
• Unilateral
• Telangiectatic retinal vessels
• Massive yellow lipid exudation
• Exudative retinal detachment
• Usually no intraocular calcified tumor

Retinoblastoma

Typically:

• Intraocular retinal mass
• Calcification common
• Tumor-associated retinal detachment
• Vitreous or subretinal seeds may be present

Because missing retinoblastoma has major consequences:

Any diagnostic uncertainty warrants evaluation by an ocular oncology or pediatric retinal specialist.

Coats Disease vs FEVR

Familial exudative vitreoretinopathy tends to show:

• Bilateral disease
• Peripheral avascular retina
• Retinal dragging
• Falx folds
• Family history in some patients

Classic Coats disease is overwhelmingly: