Anterior segment dysgenesis

Anterior segment dysgenesis (ASD) refers to a spectrum of disorders that affect the development of the front of the eye (the anterior segment), which includes the cornea, iris, ciliary body, and lens. The specific eye abnormalities (alone or in combination) vary depending on the subtype of ASD and genetic cause, and some types may also be associated with neurological abnormalities. Glaucoma develops in approximately 60% of people with ASD, during infancy or much later. Specific eye signs and symptoms of ASD may include:

• Underdevelopment of the iris (iris hypoplasia).
• An enlarged or reduced cornea diameter.
• Growth of new blood vessels (vascularization) and opacity in the cornea.
• Posterior embryotoxon (a thickened and displaced Schwalbe's line).
• Corectopia (displacement of the pupil).
• Polycoria (more than one pupillary opening).
• An abnormal iridocorneal angle (the angle formed by the iris and cornea).
• Ectopia lentis (displacement of the lens).
• Aphakia (absent lens).
• Cataracts.
• Anterior synechiae (when the iris adheres to the cornea).
• Posterior keratoconus (thinning of the cornea).

Individual disorders within the ASD spectrum include Axenfeld-Rieger syndrome (which includes disorders formerly known as Axenfeld anomaly, Axenfeld syndrome, Rieger anomaly, Rieger syndrome, and iridogoniodysgenesis) and Peters anomaly.

ASD may be caused by mutations in any of several genes and inheritance can be autosomal dominant or autosomal recessive, depending on the responsible gene.

Treatment of signs and symptoms depends on the specific features in each person with ASD and may involve medications, eye surgery, or corrective lenses for poor vision.