Most often presenting as a keyhole-shaped pupil, coloboma may affect one or both eyes.
Persons with this problem of the iris often have fairly good vision, but those with it involving the retina may have vision loss in specific parts of the visual field, which can cause problems with reading, writing, and close-up work or play.
This eye condition is estimated to occur in about one in 10,000 people. It is typically discovered at birth, although it does not always affect vision or the outward appearance of the eye.
Because this condition can be associated with other health conditions affecting the eye and other parts of the body, careful evaluation and monitoring of a child with coloboma is important. Although symptoms can be managed, there is currently no cure for the condition.
Symptoms of Coloboma
Persons with an isolated coloboma may have normal vision and no symptoms, or they may have mild to severe vision impairment. How vision is affected depends on where the gap or gaps occur in the eye. Symptoms may include:
- Keyhole-shaped pupil
- Light sensitivity or photophobia (usually occurs with iris coloboma)
- Vision impairment or loss that may not always be correctable
What Other Conditions Are Associated With Coloboma?
Coloboma may occur by itself — which is described as nonsyndromic or isolated. It may occur with other conditions or as part of a syndrome that affects other organs and tissues in the body. Some people with coloboma have associated eye abnormalities, including:
- Microphthalmia – one or both eyeballs are abnormally small
- Anophthalmia – no eyeball forms at all
- Cataract – clouding of the lens of the eye
- Glaucoma – increased pressure inside the eye that can damage the optic nerve
- Vision problems such as nearsightedness (myopia)
- Nystagmus – involuntary back-and-forth eye movements
- Retinal detachment – separation of the retina from the back of the eye
- Eyelid coloboma – gaps that occur in the eyelids are also called colobomas, but they arise from abnormalities in different structures during early development
Ocular Coloboma may be a feature of the following syndromes:
- Renal coloboma syndrome – characterized by optic nerve dysplasia and renal hypodysplasia
- CHARGE syndrome – characterized by coloboma, heart defects, atresia, retarded growth and development, genital hypoplasia (undescended testicles), and ear abnormalities
- Cat eye syndrome – characterized by coloboma, anal atresia, and an extra chromosome
- Morning glory syndrome – optic disc coloboma that may be accompanied by cranial facial, neurologic, and other symptoms
What Causes Coloboma to Develop?
The bottom line is, it results from abnormal development of the eye during the third trimester of gestation, when the eye is forming. The defect occurs when the optic fissure does not close completely. Its location depends on which part of the optic fissure fails to close.
Coloboma may occur spontaneously or it may be inherited. Persons with isolated coloboma can still pass the condition onto their children.
When it occurs as a feature of a genetic syndrome or chromosomal abnormality, it may cluster in families according to the inheritance pattern for that condition.
Environmental factors that affect early development, such as the exposure to alcohol and certain drugs during pregnancy, may increase the risk of coloboma.
How is Coloboma Diagnosed in Adults and Children?
Coloboma is often identified at birth by hospital staff, or by a parent who may notice something different about their baby’s pupil. A baby will be evaluated by an ophthalmologist who will perform a complete eye examination to determine how much of the eye is affected.
The examination typically involves use of an ophthalmoscope to look inside the baby’s eyes. The baby may be given a general anesthetic to avoid causing any distress during the examination. At this age, it is difficult to tell whether the baby will have vision problems.
A child with coloboma will be monitored closely by their ophthalmologist, and their vision will be tested on a regular basis.
In addition to an eye examination, a baby may undergo other testing to see whether any associated conditions are present, and to check his or her general health. The families of affected children may be referred for genetic counseling.
For the child with an isolated coloboma, this may involve an evaluation to determine the risk of recurrence. A child with a genetic form or a specific syndrome of which coloboma is a part, may be referred for certain genetic tests.
How Can I Manage My Coloboma?
You may not require treatment unless it is causing vision problems. If the child with a coloboma is healthy and has no other eye conditions or complications, then the recommendation may be an eye test every six months up to the age of seven years and then annually thereafter.
The purpose of the eye tests is to monitor the effect of the condition and the child’s eye health. Frequent monitoring of children with this condition is important because of the potential for the development of associated eye conditions, such as glaucoma and retinal detachment.
As children with coloboma get older, they may become concerned about the appearance of their eyes. Cosmetic contact lenses can help make the pupil look round rather than keyhole-shaped.
For children with light sensitivity, tinted glasses, sunglasses, wide-brimmed hats, and sunshades in cars can help reduce discomfort caused by bright lights or the sun.
Children with poor vision require help from an eye specialist to make the most of their sight. Affected families can also work with support services for children with visual impairment, such as those offered through the American Foundation for the Blind and National Association for Parents of Children with Visual Impairments (for example, Family Connect).