Coloboma of optic nerve

What causes coloboma of the optic nerve?

Colobomas are due to incomplete development of the eye. During the second month of development in utero, a seam-like structure called the optic fissure closes up to form the structures of the eye. When it doesn't fuse normally, it results in a coloboma in the affected location of the eye.

A coloboma may occur sporadically, it may be inherited and due to mutations in various genes, or may occur as a feature of an underlying syndrome or other genetic condition. When an underlying syndrome or genetic condition is present, the cause is assumed to be the same as that of the underlying condition. For example, when an optic nerve coloboma occurs as part of renal coloboma syndrome, it is caused by mutations in the PAX2 gene. Certain environmental factors affecting early development may also increase the risk for colobomas in general.

Many genes involved in early eye development may be responsible for colobomas in general. While some of these genes have been identified, most of them remain unknown. Most genetic mutations associated with colobomas have been identified only in very small numbers of affected people. Autosomal dominant inheritance has been reported. One gene that has been associated with coloboma of the optic nerve specifically is the PAX6 gene.

The PAX6 gene is part of a "family" of genes that are needed for forming tissues and organs during embryonic development, and for maintaining normal function of certain cells after birth. The genes in this family give the body instructions to make proteins that help control the activity of particular genes. It is thought that the PAX6 protein turns on (activates) genes involved in forming the eyes before birth, and regulating the actions of genes within many eye structures.

Last updated on 05-01-20

Diagrams/images

Coloboma of optic nerve

The Digital Reference of Ophthalmology provides an image and outlined description of optic nerve coloboma. Click on Digital Reference of Ophthalmology to view the information page.

Last updated on 04-27-20

Name: National Alliance for Eye and Vision Research (NAEVR) 1801 Rockville Pike, Suite 400
Rockville, MD, 20852, United States
Phone: 240-221-2905 Fax : 240-221-0370 Email: jamesj@eyeresearch.org Url: http://www.eyeresearch.org/
Name: Vision of Children Foundation (VOC) 12671 High Bluff Drive, Suite 300
San Diego, CA, 92130 , United States
Phone: 858-799-0810 Fax : 858-794-2348 Email: cdenofrio@visionofchildren.org Url: http://www.visionofchildren.org
Name: American Foundation for the Blind 1401 South Clark Street Suite 730
Arlington, VA, 22202, United States
Phone: 212-502-7600 Toll Free: 800-232-5463 Fax : 888-545-8331 Email: http://www.afb.org/sendMail.asp Url: http://www.afb.org/

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