Coloboma

Retino choroidal coloboma

Retino choroidal coloboma (Photo credit: Community Eye Health)

DESCRIPTION: Coloboma of the iris is a congenital (present since birth) defect of the iris of the eye.Congenital cleft in some part of the eye (commonly the iris, but may also occur in the lid(s) or pigment epithelium and choroid); caused by faulty closure during prenatal development; usually hereditary; secondary complication: cataracts. Associated conditions are: microphthalmia, polydactyly and mental retardation. Depending on the extent and location of the coloboma, there may be decreased visual acuity, nystagmus, strabismus, photophobia, and a loss of visual fields.
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A coloboma (also part of the rare Cat Eye syndrome) is a hole in one of the structures of the eye, such as the lens, eyelid, iris, retina, choroid or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure between two structures in the eye, which is present early in development in the uterus, fails to close up completely before a child is born. A coloboma can occur in one or both eyes.

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, or there may be glaucoma, nystagmus or strabismus (squint).

Some children with coloboma of the eye also have malformations in other parts of the body. There is a rare condition called CHARGE syndrome, in which coloboma is associated with cleft lip and/or palate, ear abnormalities and hearing impairment, choanal atresia, delays in growth and development, central nervous system anomalies and congenital heart defects.

Colobomas are caused by a mutation in the pax2 gene.

CHARGE association congenital defects include:

-Colobomas -Heart defects -Atresia (Choanal atresia) -Retardation -Genitourinary abnormalities -Ear abnormalities

The incidence of coloboma is estimated at around 0.5 to 0.7 per 10,000 births, making it a relatively rare condition

Coloboma of the iris may appear as a black, round hole located in or next to the colored portion of the eye (iris). It can appear as a black notch of varying depth at the edge of the pupil, giving the pupil an irregular shape. It can also appear as a split in the iris from the pupil to the edge of the iris.

A small coloboma, especially if it is not attached to the pupil, may allow a secondary image to focus on the back of the eye, causing:

*Blurred vision

*Decreased visual acuity

*Ghost image

The defect may extend to the retina, choroid, or optic nerve.

Colobomas are generally diagnosed at, or shortly after birth.

CAUSES:-

Coloboma can occur due to:

*Eye surgery

*Hereditary conditions

*Trauma to the eye

Most cases of coloboma have no known cause and are not associated with other abnormalities. A small percentage of people with coloboma have other inherited developmental abnormalities.

DIAGNOSIS:-
The doctor will take a medical history and conduct an examination.

The patient is usually an infant, and the family history will be most important.

The physical examination will include a detailed eye examination, which may involve:

Dilated exam
MRI imaging of the brain and nerves connecting the eye to the brain
After seeing your health care provider:

You may want to add a diagnosis related to a coloboma to your personal medical record.

TREATMENT:
Cosmetic contact lenses and/or sunglasses for colobomas of the iris. Optical aids may be helpful.

IMPLICATIONS: Visual fields measurement is suggested when a coloboma of some-part of the inner eye is suspected (i.e., choroid or pigment epithelium).

Contact your health care provider if:-

You notice that your child has what appears to be a hole in the iris or an unusual-shaped pupil.
Your child’s vision becomes blurred or decreased.

Note: It is appropriate to see an ophthalmologist for vision problems. Your primary health care provider may need to help rule out disorders associated with coloboma of the iris.

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Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose

Resources:

http://www.nlm.nih.gov/medlineplus/ency/article/003318.htm

http://www.tsbvi.edu/Education/anomalies/coloboma.htm

http://en.wikipedia.org/wiki/Coloboma

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