Fuchs heterochromic iridocyclitis

Fuchs heterochromic iridocyclitis (FHI), also known as Fuchs heterochromic uveitis or Fuchs uveitis syndrome, is a chronic, low-grade inflammatory condition of the eye that typically affects one eye (unilateral). It accounts for approximately 2–11% of all uveitis cases. The disease is characterized by heterochromia (a difference in iris color between the two eyes), with the affected eye usually appearing lighter due to iris stromal atrophy. Patients develop a chronic, mild anterior uveitis (inflammation of the front part of the eye) that is often painless and may go unnoticed for years. Characteristic fine, stellate (star-shaped) keratic precipitates are scattered diffusely across the corneal endothelium, and the eye may show mild flare in the anterior chamber without significant redness. The most important complications of Fuchs heterochromic iridocyclitis are cataract formation and secondary glaucoma. Cataracts develop in the majority of affected individuals over time and are often the presenting complaint that leads to diagnosis. Secondary open-angle glaucoma occurs in a significant proportion of patients and can be difficult to manage. Vitreous opacities (floaters) are also commonly observed. A distinctive clinical sign is the occurrence of fine hemorrhage in the anterior chamber (Amsler sign) following paracentesis or minor surgical trauma. The exact cause of FHI remains debated, though evidence increasingly suggests an association with rubella virus infection in many cases, supported by the detection of rubella virus-specific antibodies in the aqueous humor. The condition is considered sporadic and is not inherited. Treatment is primarily directed at managing complications rather than the inflammation itself, as the chronic low-grade uveitis typically does not respond well to corticosteroids and rarely requires aggressive anti-inflammatory therapy. Cataract surgery generally yields good visual outcomes, though careful monitoring for glaucoma is essential. Glaucoma may require medical therapy or surgical intervention. There is no cure for the underlying condition, and long-term ophthalmologic follow-up is recommended.

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