Editing Coloboma

{{short description|Hole in one of the structures of the eye}}
{{Infobox medical condition (new)
| name            = Coloboma
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| field           = [[Ophthalmology]]
| image           = Coloboma of the iris.JPG
| caption         = Coloboma in a 16-year-old female
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A '''coloboma''' (from the Greek {{lang|grc|[[wikt:κολόβωμα|κολόβωμα]]}}, meaning "defect")<ref>{{cite encyclopedia| title= coloboma| encyclopedia= [[Mosby's Medical, Nursing & Allied Health Dictionary]] |edition= 4th |publisher= Mosby Year-Book| year= 1994| page= 361 | isbn= 9780801672255}}</ref> is a hole in one of the structures of the [[human eye|eye]], such as the [[iris (anatomy)|iris]], [[retina]], [[choroid]], or [[optic disc]]. The hole is present from birth and can be caused when a gap called the [[Choroidal fissure|choroid fissure]], which is present during early stages of prenatal development, fails to close up completely before a child is born. Ocular coloboma is relatively uncommon, affecting less than one in every 10,000 births.

The classical description in medical literature is of a [[keyhole]]-shaped defect. A coloboma can occur in one eye (unilateral) or both eyes (bilateral). Most cases of coloboma affect only the iris. The level of vision impairment of those with a coloboma can range from having no vision problems to being able to see only light or dark, depending on the position and extent of the coloboma (or colobomata if more than one is present).

==Signs and symptoms==
[[File:Coloboma.jpg|thumb|Iris coloboma in the right eye of a 10-month-old child. The pupil cannot contract to a smaller size than pictured, but may still be able to dilate in low light.]]

Visual effects may be mild to more severe depending on the size and location of the coloboma. If, for example, only a small part of the iris is missing, the vision may be normal; when a large part of the retina or (especially) [[optic nerve]] is missing, the vision may be poor. Commonly posterior colobomata affect the inferior retina, with resultant deficit in the superior visual field. Other conditions can be associated with a coloboma. Sometimes, the eye may be reduced in size, a condition called [[microphthalmia]]. [[Glaucoma]], [[pathologic nystagmus|nystagmus]], [[scotoma]], or [[strabismus]] may also occur.

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

* [[CHARGE syndrome]], a term that came into use as an [[acronym]] for the set of unusual congenital features seen in a number of newborn children.<ref name="Pagon">{{cite journal |vauthors=Pagon RA, Graham JM, Zonana J, Yong SL |title=Coloboma, congenital heart disease, and choanal atresia with multiple anomalies: CHARGE association |journal=J. Pediatr. |volume=99 |issue=2 |pages=223–7 |year=1981 |pmid=6166737 |doi=10.1016/S0022-3476(81)80454-4}}</ref> The letters stand for: {{strong|c}}oloboma of the eye, {{strong|h}}eart defects, [[Atresia|{{strong|a}}tresia]] of the nasal [[choanae]], {{strong|r}}etardation of growth and/or development, [[Genital|{{strong|g}}enital]] and/or urinary abnormalities, and {{strong|e}}ar abnormalities and deafness. Although these features are no longer used in making a diagnosis, the name has remained.
* [[Cat eye syndrome]], caused by the short arm (p) and a small section of the long arm (q) of human [[chromosome 22]] being present three (trisomic) or four times (tetrasomic) instead of the usual two times. The term "cat eye" was coined because of the particular appearance of the vertical colobomas in the eyes of some patients. 
* [[Patau syndrome]] (trisomy 13), a chromosomal abnormality that can cause a number of deformities, some of which include structural eye defects, including microphthalmia, [[Peters anomaly]], [[cataract]], iris and/or [[fundus (eye)|fundus]] coloboma, retinal dysplasia or [[retinal detachment]], sensory [[Pathologic nystagmus|nystagmus]], [[cortical visual loss]], and [[optic nerve hypoplasia]].
* [[Treacher Collins syndrome]], autosomal dominant syndrome caused by mutation of ''[[TCOF1]]''. Coloboma is part of a set of characteristic [[facies (medical)|facies]] that features craniofacial malformations, such as downslanting eyes, ear anomalies, or hypoplasia of zygomatic bone and jaw (micrognathia).
* Tilted disc syndrome, an unusual congenital malformation associated with [[myopia|myopic]] [[astigmatism]] characterized by tilting of the intraocular tip of the optic nerve (the optic disc), also known as [[Ernst Fuchs (doctor)|Fuchs]] coloboma.

==Causes==
Coloboma can be associated with a mutation in the ''[[PAX2]]'' gene.<ref name="pmid9783702">{{cite journal |display-authors= 3| vauthors=Cunliffe HE, McNoe LA, Ward TA, Devriendt K, Brunner HG, Eccles MR |title=The prevalence of PAX2 mutations in patients with isolated coloboma or colobomata associated with urogenital anomalies |journal=J. Med. Genet. |volume=35 |issue=10 |pages=806–12 |date=October 1998 |pmid=9783702 |pmc=1051454 |doi= 10.1136/jmg.35.10.806}}</ref>

Eye abnormalities have been shown to occur in over 90% of children with [[fetal alcohol syndrome]].<ref>{{cite journal | pmc = 2773598 | pmid=19907681 | volume=78 | title=Eye abnormalities in fetal alcohol syndrome. | date=Sep 2009 | journal=Ulster Med J | pages=164–5| last1=Abdelrahman | first1=A. | last2=Conn | first2=R. | issue=3 }}</ref>

==Diagnosis==
Typically a coloboma appears oval- or comet-shaped with round end towards the centre. There may be a few vessels (retinal or choroidal) at the edges. The surface may have irregular depression.

== Treatment==
Coloboma of the iris may be treated in a number of ways. A simple cosmetic solution is a specialized cosmetic contact lens with an artificial pupil aperture. Surgical repair of the iris defect is also possible. Surgeons can close the defect by stitching in some cases. 

Vision can be improved with glasses, contact lenses or even laser eye surgery but may be limited if the retina is affected or there is [[amblyopia]].<ref>{{cite web| work= RNIB.org.uk| title= Coloboma| url= http://www.rnib.org.uk/eye-health-eye-conditions-z-eye-conditions/coloboma#P92_9303| publisher= [[Royal National Institute of Blind People]]| date= | access-date= January 7, 2021| archive-date= April 28, 2018| archive-url= https://web.archive.org/web/20180428124245/http://www.rnib.org.uk/eye-health-eye-conditions-z-eye-conditions/coloboma#P92_9303| url-status= dead}}</ref>

==Epidemiology==
The number of cases is around 5 to 7 per 100,000 births, making it a relatively rare condition.<ref>{{cite journal |last1= Hornby| first1= SJ| last2= Adolph| first2= S| last3= Gilbert| first3= CE|last4=Dandona|first4=L|last5=Foster|first5=A| display-authors= 3| title=Visual acuity in children with coloboma: clinical features and a new phenotypic classification system| journal=Ophthalmology |date=Mar 2000|volume=107|issue=3|pages=511–20|pmid=10711890|doi=10.1016/S0161-6420(99)00140-2}}</ref>

==Notable cases==
{{Unreferenced section|date=December 2019}}
Notable people with coloboma include actor [[John Ritter]], model/actress [[Karolina Wydra]], ''[[The New York Times]]'' columnist [[Andrew Ross Sorkin]], pop singer songwriter [[Lachi (artist)|Lachi]], U.S. Olympic medalist [[Stephen Nedoroscik]], and [[George Soros]]. [[Disappearance of Madeleine McCann|Madeleine McCann]], a young girl who went missing in Portugal in 2007, does not have the condition. She has a freckle under her pupil. Her unique eye was a large part of her parents' media appeal to find her.

== References ==
{{reflist}}

== External links ==
{{Commons category}}
* [http://www.macs.org.uk/ Micro & Anophthalmic Children's Society]

{{Congenital malformations and deformations of eye, ear, face and neck}}
{{Medical resources
|   ICD10          = {{ICD10|Q|10|3|q|10}}, {{ICD10|Q|12|2|q|10}}, {{ICD10|Q|13|0|q|10}}, {{ICD10|Q|14|2|q|10}}, {{ICD10|Q|14|8|q|10}} 
|   ICD9           = {{ICD9|377.23}}, {{ICD9|743.4}}, {{ICD9|743.46}}, {{ICD9|743.52}}, {{ICD9|743.57}} 
|   ICDO           = 
|   OMIM           = 120200
|   MedlinePlus    = 003318
|   eMedicineSubj  = 
|   eMedicineTopic = 
|   DiseasesDB     = 29894
|   MeshID         = D003103 
}}

[[Category:Eye diseases]]
[[Category:Congenital disorders of eyes]]