Ophthalmology – Iris Atrophy

Basics

Description

Iris atrophy is thinning or loss of iris tissue that can occur in a wide variety of ocular disorders. It may involve the iris stroma, iris pigment epithelium, or both.

The pattern, laterality, and associated ocular findings are particularly useful in determining the underlying cause.

Pediatric Considerations

In children, iris atrophy or iris transillumination abnormalities may suggest congenital or developmental disorders such as:

• Axenfeld–Rieger syndrome
• Ocular albinism

Pregnancy Considerations

Iris atrophy associated with uveitis during pregnancy may occur with infectious or inflammatory disorders such as:

• Herpes simplex virus (HSV)
• Varicella-zoster virus (VZV)
• Fuchs uveitis syndrome

The underlying disorder should be identified because treatment considerations may differ during pregnancy.

Epidemiology

The incidence and prevalence of iris atrophy depend entirely on the underlying disease.

ICE syndrome is rare, whereas iris atrophy is common in several forms of anterior uveitis.

In Fuchs uveitis syndrome, iris stromal atrophy is a characteristic and frequent finding.

Risk Factors

Important risk factors include:

• Chronic or recurrent anterior uveitis
• Herpetic eye disease
• Herpes zoster ophthalmicus
• Glaucoma
• Pigment dispersion syndrome
• Previous ocular trauma
• Previous intraocular surgery
• Intraocular lens–iris chafing
• Congenital anterior segment abnormalities
• Ocular ischemia

Genetics

Axenfeld–Rieger syndrome is usually inherited in an autosomal dominant pattern.

Ocular albinism and related forms of albinism have several inheritance patterns depending on the underlying genetic disorder.

Pathophysiology

The mechanism of iris atrophy varies according to its cause.

Chronic Inflammation

Repeated or persistent inflammation can destroy the iris stroma, producing:

• Loss of normal iris architecture
• Stromal thinning
• Pigment loss
• Transillumination defects

Herpetic Uveitis

HSV and VZV-associated anterior uveitis can produce ischemic and inflammatory damage to the iris, often resulting in characteristic sectoral or patchy atrophy.

Axenfeld–Rieger Syndrome

Iris abnormalities result from abnormal development of the anterior segment.

Ocular Albinism

Reduced iris pigmentation results from abnormal melanin production or melanosome abnormalities, producing prominent iris transillumination.

Pigment Dispersion Syndrome

Posterior bowing of the iris allows the posterior iris pigment epithelium to rub against the lens zonules. This produces loss of pigment and characteristic radial or spoke-like transillumination defects.

ICE Syndrome

Abnormal corneal endothelial cells proliferate over the anterior chamber angle and iris. Contraction of this membrane causes progressive iris distortion and atrophy.

Etiology

Important causes include:

• Herpes simplex anterior uveitis
• Herpes zoster anterior uveitis
• Fuchs uveitis syndrome
• Pigment dispersion syndrome
• Pigmentary glaucoma
• Pseudophakic pigment dispersion from iris–IOL chafing
• Ocular trauma
• Previous ocular surgery
• ICE syndrome
• Axenfeld–Rieger syndrome
• Ocular albinism
• Ischemic iridopathy
• Diabetes-associated iris ischemia
• Ocular ischemic syndrome
• Systemic vascular disorders

Commonly Associated Conditions

Iris atrophy is frequently associated with:

• Anterior uveitis
• Glaucoma
• Cataract

These associated conditions may ultimately be more important for vision than the iris atrophy itself.

Diagnosis

History

A careful history is essential because iris atrophy is a clinical sign rather than a single disease.

Ask about:

• Recurrent red eye
• Eye pain
• Photophobia
• Previous episodes of uveitis
• Blurred or decreased vision
• History of elevated IOP or glaucoma
• Herpes simplex infection
• Herpes zoster ophthalmicus
• Ocular trauma
• Previous ocular surgery
• Cataract surgery and intraocular lens implantation
• Family history of congenital ocular abnormalities

The age at onset and whether the condition is unilateral or bilateral can significantly narrow the differential diagnosis.

Physical Examination

Visual Acuity and Intraocular Pressure

Both should be carefully documented.

Elevated IOP can accompany:

• HSV anterior uveitis
• VZV anterior uveitis
• Fuchs uveitis syndrome
• Chronic anterior uveitis
• ICE syndrome
• Axenfeld–Rieger syndrome
• Pigment dispersion syndrome

Therefore, glaucoma must always be considered in a patient with iris atrophy.

Laterality

Laterality provides an important diagnostic clue.

Usually unilateral:

• ICE syndrome
• Herpetic anterior uveitis
• Fuchs uveitis syndrome, although bilateral cases occur
• Trauma or surgical injury

Usually bilateral:

• Axenfeld–Rieger syndrome
• Ocular albinism
• Pigment dispersion syndrome

Slit-Lamp Examination

Iris atrophy can be subtle on routine examination.

Retroillumination or transillumination is particularly useful for demonstrating areas of pigment loss.

The pattern of iris atrophy can provide an important clue to the diagnosis.

Pupillary Margin Atrophy

Atrophy around the pupillary margin, particularly when associated with persistent pupillary dilation, can occur with HSV anterior uveitis.

Sectoral Iris Atrophy

Sectoral or patchy iris atrophy strongly suggests herpetic anterior uveitis, particularly VZV or HSV.

Diffuse Iris Atrophy

Diffuse stromal atrophy is characteristic of Fuchs uveitis syndrome.

Heterochromia may result, although it is not always clinically obvious.

Radial or Spoke-Like Atrophy

Radial transillumination defects suggest pigment dispersion syndrome.

They result from mechanical rubbing between the posterior iris pigment epithelium and the lens zonules.

Corectopia and Iris Holes

The combination of:

• Corectopia
• Ectropion uveae
• Progressive iris atrophy
• Pseudopolycoria

should raise suspicion for ICE syndrome.

Similar developmental abnormalities can occur with Axenfeld–Rieger syndrome, but that disorder is usually bilateral and congenital.

Corneal Examination

The cornea can provide important clues to the underlying diagnosis.

Corneal Edema

Corneal edema, especially in a unilateral eye with iris distortion and peripheral anterior synechiae, suggests ICE syndrome.

Keratic Precipitates

Keratic precipitates indicate current or previous anterior segment inflammation.

Diffuse KPs may occur in:

• Herpetic anterior uveitis
• Fuchs uveitis syndrome

Gonioscopy

Gonioscopy should be performed whenever possible.

Peripheral Anterior Synechiae

PAS may indicate:

• Previous or chronic uveitis
• ICE syndrome
• Other causes of secondary angle closure

Heavy Trabecular Pigmentation

Marked pigmentation of the trabecular meshwork supports pigment dispersion syndrome.

Lens Examination

Cataract may be evidence of:

• Chronic uveitis
• Previous ocular inflammation
• Previous trauma
• Previous intraocular surgery

In pseudophakic patients, consider mechanical iris chafing from an intraocular lens when the iris atrophy corresponds to the position of an IOL component.

Posterior Segment Examination

The optic nerve should be carefully examined for glaucomatous cupping.

The retina should be evaluated for evidence of:

• Ocular albinism
• Retinal or choroidal ischemia
• Other manifestations of ocular ischemic syndrome

Diagnostic Tests

Laboratory Testing

Routine laboratory testing is usually unnecessary.

Testing should instead be directed toward the suspected underlying cause.

When the diagnosis of viral anterior uveitis is uncertain, aqueous humor PCR may be useful for detecting viral DNA, particularly:

• HSV
• VZV

Other targeted investigations may be appropriate depending on the clinical presentation.

Photography

Slit-lamp photographs can document:

• Iris architecture
• Corectopia
• Areas of stromal atrophy
• Progressive changes

Transillumination photographs are particularly useful for documenting pigment epithelial defects.

Anterior-Segment Imaging

When mechanical iris chafing is suspected, ultrasound biomicroscopy (UBM) or other anterior-segment imaging can help determine the relationship between the iris and:

• Intraocular lens
• IOL haptics
• Crystalline lens
• Other anterior segment structures

Differential Diagnosis

The major differential diagnoses include:

• Herpes simplex anterior uveitis
• Herpes zoster anterior uveitis
• Fuchs uveitis syndrome
• Pigment dispersion syndrome
• Pigmentary glaucoma
• Pseudophakic iris chafing
• Previous ocular trauma
• Iatrogenic iris damage
• ICE syndrome
• Axenfeld–Rieger syndrome
• Ocular albinism
• Diabetic ischemic iridopathy
• Ocular ischemic syndrome

Treatment

There is generally no treatment that restores already atrophied iris tissue. Management is directed toward the underlying disease and its complications.

Uveitis

Active inflammation may require topical corticosteroids or other anti-inflammatory therapy depending on the cause.

When herpetic disease is suspected or confirmed, appropriate systemic antiviral therapy may be required.

Steroids in infectious uveitis should be used in the appropriate clinical context and generally with treatment directed at the underlying infection when indicated.

Glaucoma

Elevated IOP should be treated appropriately.

Management may include:

• Topical pressure-lowering medications
• Laser treatment in selected disorders
• Glaucoma surgery when medical treatment is inadequate

Patients with uncontrolled IOP or progressive optic nerve/visual field damage should be referred to a glaucoma specialist.

Cataract

Visually significant cataract may require cataract extraction.

Surgical planning should take into account the underlying cause of iris atrophy, particularly when there is:

• Chronic uveitis
• Poor pupillary dilation
• Iris instability
• Extensive iris defects
• Glaucoma

Issues for Referral

Referral should be considered for patients with:

• Uncontrolled glaucoma
• Progressive visual field loss
• Significant corneal disease
• Uncertain uveitis etiology
• Suspected ICE syndrome
• Suspected congenital anterior segment dysgenesis

Children with suspected Axenfeld–Rieger syndrome or albinism may require pediatric and genetic evaluation.

Ongoing Care

Follow-Up

Follow-up frequency depends on the underlying condition.

Patients should be monitored for the major complications associated with iris atrophy, particularly:

• Glaucoma
• Cataract
• Recurrent or chronic uveitis
• Progressive visual loss

Patients with glaucoma require serial assessment of IOP, optic nerve structure, OCT when appropriate, and visual fields.

Patient Education

Patients should understand that iris atrophy is usually a sign of an underlying ocular disorder rather than an isolated disease.

Regular follow-up is important because glaucoma may progress without producing early symptoms.

Patients prescribed glaucoma medications should be counseled regarding adherence.

When a hereditary disorder such as Axenfeld–Rieger syndrome or albinism is identified, genetic counseling may be appropriate.

Prognosis

The prognosis depends primarily on the underlying cause and associated complications.

Iris atrophy itself may remain stable or progress depending on the disorder. Visual prognosis is usually determined by associated conditions such as:

• Glaucoma
• Cataract
• Chronic uveitis
• Corneal disease
• Ocular ischemia

Key clinical clue: the pattern of iris atrophy is diagnostically useful—sectoral atrophy suggests herpetic uveitis, diffuse stromal atrophy suggests Fuchs uveitis syndrome, radial transillumination defects suggest pigment dispersion syndrome, and progressive iris distortion with corectopia/pseudopolycoria suggests ICE syndrome.