History
FHI may be detected in the asymptomatic patient during a routine eye examination. [24] The most common reported symptoms include floaters cause by vitreous opacities and visual deterioration caused by cataract formation, while pain and perilimbal injection are rare. Some patients may present with symptoms of acutely elevated intraocular pressure (eg, mild pain, blurry vision, colored haloes around lights).
Physical Manifestations
Iris heterochromia develops as a result of gradual, progressive, irreversible atrophy of the iris stroma. Heterochromia can be subtle or even absent in patients with darkly pigmented irides and in patients with bilateral involvement. [25, 26, 27] Heterochromia is caused by atrophy of the anterior border of the iris. Progressive atrophy makes the brown iris appear less brown, whereas inflammation causing atrophy of a light colored iris will result in an apparent deepening of the color secondary to revealing the underlying iris pigmented epithelium. [28]
Anterior chamber inflammation is unilateral in 90% of patients and bilateral in 10%. [1, 2, 29] Inflammation, when present, is usually mild, and keratic precipitates are essentially pathognomonic for FHI. The keratic precipitates in FHI are small, stellate, nonpigmented, and translucent and scattered over the entire corneal endothelium. [1, 2, 29] In occasional cases, inflammation flares up to a moderate level, requiring a short course of topical corticosteroid therapy. High-dose or long-term topical corticosteroids are generally not beneficial to patients with FHI. In fact, long-term therapy hastens the development of complications, such as cataracts and glaucoma.
Cataract formation is a common cause of decreased visual acuity in FHI and usually commences as a posterior subcapsular cataract. It matures at variable speeds depending on the amount of inflammation present and frequency of corticosteroid use. [2]
The prevalence of secondary glaucoma is reported to be as high as 59%, and it is the most common cause of permanent visual loss in patients with FHI. The presence of elevated intraocular pressure is multifactorial in origin. Degenerative changes of the trabecular meshwork are the most common cause of secondary glaucoma. Other factors leading to the development of secondary glaucoma include inflammation of the trabecular meshwork, long-term corticosteroid therapy, inhibition of uveoscleral outflow mechanisms, presence of peripheral anterior synechiae, and neovascularization of the trabecular meshwork. [2]
Iris nodules may be present at the pupillary margin or throughout the stroma of the iris. [25] Posterior synechiae do not usually occur in patients with FHI. [30] Rubeosis over the anterior chamber angle and iris surface has also been reported. The blood vessels found in the iridocorneal angle and iris may sheer and lead to hyphema after any surgical intervention involving the anterior chamber. This is known as Amsler sign. [31]
Complications
See the list below:
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Cataracts
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Secondary glaucoma
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Vitreous debris that obscures vision
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Dilated pupil
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Corneal edema (rare)
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Retinal detachment (rare)
