Heterochromia: Encyclopedia II - Heterochromia - Classfication based on etiology

Heterochromia - Classfication based on etiology

Although a distinction is frequently made between heterochromia that affects an eye completely or only partially, it is often classified as either congenital or acquired with mention as to whether the affected iris or portion of the iris is darker or lighter.

Heterochromia - Congenital heterochromia

Heterochromia that is congenital is usually inherited as an autosomal dominant trait.

• Lisch nodules - iris hamartomas seen in neurofibromatosis.
• Ocular melanosis - a condition characterized by increased pigmentation of the uveal tract, episclera, and anterior chamber angle.
• Pigment dispersion syndrome - a condition characterized by loss of pigmentation from the posterior iris surface which is disseminated intraocularly and deposited on various intraocular structures, including the anterior surface of the iris.
• Sturge-Weber syndrome - a syndrome characterized by a port-wine stain nevus in the distribution of the trigeminal nerve, homolateral meningeal angioma with intracranial calcification and neurologic signs, and angioma of the choroid, often with secondary glaucoma [2].

• Simple heterochromia - a rare condition characterized by the absence of other ocular or systemic problems. The lighter eye is typically regarding as the affected eye as it usually shows iris hypoplasia. It may affect an iris completely or only partially.
• Congenital Horner's syndrome - sometimes inherited, although usually acquired
• Waardenburg's syndrome - a syndrome in which heterochromia presents as a bilateral iris hypochromia in some cases.
• Piebaldism - similar to Waardenburg's syndrome, a rare disorder of melanocyte development characterized by a white forelock and multiple symmetrical hypopigmented or depigmented macules.
• Hirschsprung's disease - a bowel disorder associated with heterochromia in the form of a sector hypochromia. The affected sectors have been shown to have reduced numbers of melanocytes and decreased stromal pigmentation. [3]

Heterochromia - Acquired heterochromia

Heterochromia that is acquired is usually due to injury, inflammation, the use of certain eyedrops, or tumors.

• Deposition of material
  • Siderosis - iron deposition within ocular tissues due to a penetrating injury and a retained iron-containing, intraocular foreign body.
  • Hemosiderosis - long standing hyphema (blood in the anterior chamber) following blunt trauma to the eye may lead to iron deposition from blood products
• Use of certain eyedrops - prostaglandin analogues (latanoprost, isopropyl unoprostone, travoprost, and bimatoprost) are used topically to lower intraocular pressure in glaucoma patients. A concentric heterochromia has developed in some patients applying these drugs. The stroma around the iris sphincter muscle becomes darker than the peripheral stroma. A stimulation of melanin synthesis within iris melanocytes has been postulated.
• Neoplasm - Nevi and melanomatous tumors.

• Fuchs' heterochromic iridocyclitis - a condition characterized by a low grade, a symptomatic uveitis in which the iris in the affected eye becomes hypochromic and has a washed-out, somewhat moth eaten appearance. The heterochromia can be very subtle, especially in patients with lighter colored irides. It is often most easily seen in daylight.
• Acquired Horner's syndrome - usually acquired, as in neuroblastoma, although sometimes inherited.
• Neoplasm - Melanomas can also be very lightly pigmented, and a lighter colored iris may be a rare manifestation of metastatic disease to the eye.

Adapted from the Wikipedia article "Classfication based on etiology", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki