Coloboma

Coloboma
Classification and external resources
Specialty medical genetics
ICD-10 Q10.3, Q12.2, Q13.0, Q14.2, Q14.8
ICD-9-CM 377.23, 743.4, 743.46, 743.52, 743.57
OMIM 120200
DiseasesDB 29894
MedlinePlus 003318
Patient UK Coloboma
MeSH D003103

A coloboma (from the Greek koloboma, meaning defect,[1]) is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure, which is present during early stages of prenatal development, fails to close up completely before a child is born. The classical description in medical literature is of a key-hole shaped defect. A coloboma can occur in one eye (unilateral) or both eyes (bilateral). Most cases of coloboma affect only the iris. People with coloboma may have no vision problems or may be blind, depending on severity. It affects less than one in every 10,000 births.

Signs and symptoms

The effects a coloboma has on the vision can be mild or more severe depending on the size and location of the gap. If, for example, only a small part of the iris is missing, vision may be normal, whereas if a large part of the retina or optic nerve is missing, vision may be poor and a large part of the visual field may be missing. This is more likely to cause problems with mobility if the lower visual field is absent. Other conditions can be associated with a coloboma. Sometimes, the eye may be reduced in size, a condition called microphthalmia. Glaucoma, nystagmus, scotoma, or strabismus may also occur.

Causes

Colobomas can be associated with a mutation in the PAX2 gene.[2]

Eye abnormalities having been shown to occur in over 90% of children with the Fetal alcohol syndrome.[3]

Related conditions

Other ocular malformations that include coloboma or are related to it:

Epidemiology

The number of cases is around 0.5 to 0.7 per 10,000 births, making it a relatively rare condition.[5]

Treatment

No treatment is available for the visual impairment caused by coloboma at present. Specialized contact lenses can be used later in life for colobomas of the iris, and glasses can be used to help with vision problems.[6]

Notable cases

Notable people with coloboma include John Ritter, New York Times columnist Andrew Ross Sorkin, tennis player Arnaud Clément, alternative rock singer songwriter Lachi, and Madeleine McCann. McCann, a British girl, disappeared from the holiday apartment rented by her parents in May 2007 just before her fourth birthday. Posters and online campaigns promoting the search for Madeleine use the word "Look" with the first "O" in the word being drawn in the shape of a coloboma radius extending from the pupil at the 7 o'clock position.

References

  1. coloboma, Mosby's Medical, Nursing & Allied Health Dictionary, Fourth Edition, Mosby Year-Book, 1994, p. 361
  2. Cunliffe HE, McNoe LA, Ward TA, Devriendt K, Brunner HG, Eccles MR (October 1998). "The prevalence of PAX2 mutations in patients with isolated colobomas or colobomas associated with urogenital anomalies". J. Med. Genet. 35 (10): 806–12. doi:10.1136/jmg.35.10.806. PMC 1051454. PMID 9783702.
  3. "Eye abnormalities in fetal alcohol syndrome.". Ulster Med J 78: 164–5. Sep 2009. PMC 2773598. PMID 19907681.
  4. Pagon RA, Graham JM, Zonana J, Yong SL (1981). "Coloboma, congenital heart disease, and choanal atresia with multiple anomalies: CHARGE association". J. Pediatr. 99 (2): 223–7. doi:10.1016/S0022-3476(81)80454-4. PMID 6166737.
  5. Hornby, SJ; Adolph, S; Gilbert, CE; Dandona, L; Foster, A (Mar 2000). "Visual acuity in children with coloboma: clinical features and a new phenotypic classification system.". Ophthalmology 107 (3): 511–20. doi:10.1016/S0161-6420(99)00140-2. PMID 10711890.
  6. RNIB database - Supporting blind and partially sighted people - Coloboma; http://www.rnib.org.uk/eye-health-eye-conditions-z-eye-conditions/coloboma#P92_9303

External links

This article is issued from Wikipedia - version of the Monday, April 04, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.