Anophthalmia and microphthalmia are disorders that affect eye development before birth. Microphthalmia is a birth defect in which one or both eyes do not develop fully and are abnormally small. Anophthalmia is a more severe birth defect in which one or both eyes do not form at all. While people who have anophthalmia have no vision in the affected eye, people who have microphthalmia may or may not have significant vision loss. Because both conditions are characterized by impaired eye development, anophthalmia and microphthalmia are often considered to be related disorders (anophthalmia/microphthalmia).

Variants (also called mutations) in one of the many genes that are involved in the early development of the eye can cause anophthalmia or microphthalmia. Researchers believe that variants in as many as 90 different genes may cause these conditions. Many of the genes that are associated with anophthalmia and microphthalmia have been identified in only a very small number of affected individuals.

Microphthalmia occurs in approximately 1 in 7,000 people, while anophthalmia occurs in approximately 1 in 30,000 people.

Anophthalmia and microphthalmia can be inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Many cases result from new (de novo) variants in the gene that occur during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or during early embryonic development. These affected individuals typically have no history of the disorder in their family. In a small number of cases, an unaffected parent has the variant only in their sperm or egg cells. This phenomenon is called germline mosaicism. Cases of anophthalmia or microphthalmia that are caused by variants in the SOX2 and OTX2 genes are typically inherited in an autosomal dominant pattern.

Published Date: July 02, 2025
Published By: National Institutes of Health