Ramin Schadlu

BASICS

DESCRIPTION

• Typically FHI is a unilateral chronic, recurrent anterior uveitis that can be asymptomatic or cause mild blurring and decreased vision. Recent articles have suggested a greater bilateral incidence than previously reported.

– The causative role of rubella virus in FHI has been established (3).

– There is a high association of glaucoma and cataract with FHI.

Pediatric Considerations

The number of cases of Fuchs heterochromic iridocyclitis (FHI) has decreased among those born after introduction of the rubella vaccination program in 1969 in the US. Parents of children diagnosed with FHI should be questioned regarding vaccination history (1)[A].

Pregnancy Considerations

Pregnant patients with clinical findings consistent with FHI should be tested for rubella immunity due to the risk of congenital rubella syndrome, which is especially serious when the virus is contracted during early pregnancy (2)[B].

EPIDEMIOLOGY

Incidence

• FHI accounted for less than 6% of all cases of anterior uveitis in a tertiary care setting (1).

– The incidence of FHI decreased dramatically in patients born after 1968 due to the introduction of the rubella vaccine in 1969 (1).

Prevalence

The prevalence is <1%, but is likely underreported due to the lack of symptoms, and minimal signs in the majority of patients.

RISK FACTORS

• Risk factors include no personal or maternal history of rubella vaccination, or coming from a country without a rubella vaccination program.

– Due to the minimally symptomatic uveitis, patients who do not receive regular examinations may present with vision loss secondary to cataract and/or advanced glaucoma.

Genetics

No genetic associations for FHI have been found.

GENERAL PREVENTION

Universal rubella vaccination is recommended.

PATHOPHYSIOLOGY

• Most cases are associated with chronic rubella virus infection.

– The ocular inflammation associated with FHI is a local immune response driven by the rubella virus antigen. A CD8-positive T cell immune response mediates the inflammation (3).

ETIOLOGY

• Elevated levels of rubella antibodies (measured via a modified Goldmann–Witmer Index) were identified in the aqueous humor of 52 of 52 patients with FHI (3).

• The rubella virus (a single-stranded RNA virus) genome was identified in 5 of 28 specimens tested. Persistent virus genome is preferentially detected in younger patients (3).

COMMONLY ASSOCIATED CONDITIONS

• Cataracts are present in approximately ¾ of patients with FHI.

• Glaucoma is associated with FHI in 15% of patients (4).

DIAGNOSIS

HISTORY

• Patients are typically young and often asymptomatic.

– Complaints may include progressive iris heterochromia, unilateral mild visual disturbance, mild ocular discomfort, and occasionally floaters.

– Eye pain and redness are rare.

PHYSICAL EXAM

• Heterochromia is common (70% of patients) (4).

– An affected dark eye will appear lighter due to iris atrophy. If the eyes are blue, the affected eye may appear darker due to visualization of the underlying iris pigment epithelium.

– Heterochromia will not be evident in bilateral cases of FHI (6% of cases) (3).

• The affected eye typically is white and quiet on external exam.

• The characteristic diffuse, stellate nongranulomatous keratic precipitates are ubiquitous, although may not be evident on presentation.

• Cataracts develop in approximately ¾ of eyes with FHI (4).

• Glaucoma occurs in approximately 15% of eyes and may require surgical intervention (4).

• Abnormal bridging vessels in the anterior chamber angle may be seen on gonioscopy.

• Vitreous opacities may be present, and can cause visual symptoms. Chorioretinal scars may also be seen (2)

– Posterior segment involvement is otherwise uncommon in FHI, although cystoid macular edema may be seen.

• Peripheral anterior synechiae and posterior synechiae are not typical for FHI.

DIAGNOSTIC TESTS & INTERPRETATION

Lab

Initial lab tests

• Clinical signs may be sufficient to make the diagnosis of FHI. However, often the signs are not present at the same time. A laboratory supported diagnosis may be made by detection of intraocular rubella antibody (100% specificity). Absence of rubella antibody in the aqueous humor makes the diagnosis of FHI unlikely.

– Increased rubella antibody index (AI) (modified Goldmann–Witmer Index) is not specific when <40. However in conjunction with clinical findings, an increased AI has a very high positive predictive value.

• Oligoclonal IgG has 87% sensitivity for FHI and can be used for screening of unspecified ocular inflammation (3)[A].

Follow-up & special considerations

FHI is a chronic disease. Patients must be followed at regular intervals to monitor intraocular pressure and cataract formation.

Imaging

External photos and slit lamp photos may be obtained to monitor heterochromia, iris atrophy, and cataracts.

Pathological Findings

Infiltrating plasma cells and lymphocytes seen in pathological specimens support viral-induced inflammation as the etiology for FHI.

DIFFERENTIAL DIAGNOSIS

• Other causes of unilateral anterior uveitis.

– Herpes Simplex Virus

– Herpes Zoster Virus

– Toxoplasmosis

– Posner–Schlossman syndrome (glaucomatocyclitic crisis)

• Other causes of iris heterochromia.

– Horner’s syndrome

– Malignant melanoma of the iris

TREATMENT

MEDICATION

• Topical steroid treatment may be withheld if the inflammation is mild. The effect of steroid eyedrops in controlling FHI-related inflammation is minimal, and may hasten cataract formation and cause secondary glaucoma. However, patients should be monitored closely for worsening inflammation.

• Secondary glaucoma should be treated aggressively with topical drops and surgery, if indicated.

ADDITIONAL TREATMENT

Issues for Referral

Patients in whom the intraocular pressure is not controlled with topical drops, or who have progressive visual field loss, should be referred to a glaucoma specialist.

SURGERY/OTHER PROCEDURES

• Cataract surgery and glaucoma surgery may be complicated by intraoperative or postoperative hyphema due to the abnormal vessels bridging the anterior chamber angle (Amsler’s sign).

– Perioperative topical and/or oral steroid treatment should be used to minimize surgery-induced inflammation.

– Posterior capsule opacification, glaucoma, and vitreous opacity may limit visual outcomes following cataract surgery (4).

• Pars plana vitrectomy may be indicated to clear visually-significant vitreous opacities.

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patients need regularly scheduled follow-up visits depending on the presence of glaucoma and cataracts. Since FHI is often asymptomatic, patients may not notice recurrences.

PATIENT EDUCATION

Patients should be educated on the need for regular follow-up and the importance of compliance with glaucoma medications.

PROGNOSIS

Visual prognosis can be good, as long as glaucoma and any posterior segment complications are controlled.

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