COLOBOMA

Ophthalmologist Carolina Valdivia, MD explains coloboma, a congenital eye condition in which the choroid fissure fails to close, causing certain structures of the eye not to form properly.

Dear Dr. Valdivia. My 4-month-old daughter recently was diagnosed with coloboma of the iris. Both pupils are stretched to the bottom and the defect goes to a structure at the back of the eye that I think is called the fundus.

The doctor told me that the fundus is not affected in her right eye. However, in the left eye, the fundus and optic nerve are involved. Additionally, her left eye is smaller than normal and does not appear to be well coordinated with her right eye. The doctor said she cannot see with this eye.

I am very worried about my daughter. From my heart, can you please give me an opinion about what I can expect? Is there something that can be done to help her regain sight in her left eye? I appreciate any advice you can give me.



Thank you for your question and for your interest in glaucoma-eye-info.com.

I am sorry to learn that you are facing this challenge and I wish the best for both you and your baby girl. While I understand your sense of desperation, the most important thing to remember is that there is hope. Despite having an eye problem, your daughter can grow to live a fulfilling and productive life.

Some information sources incorrectly describe coloboma as a hole in the eye. Technically, it is not. Instead, it means that certain structures or parts within the eye have not fully formed. It can affect the iris (colored part of the eye), the lens (part of the eye that helps focus light onto the retina), the choroid (a thin network of blood vessels that help to keep the retina healthy), the retina, or the optic nerve. The problem results in a gap that can be large or small and typically is located at the bottom part of the eye. When the eye is smaller than normal, as is the case with your daughter's left eye, this condition is called microphthalmos, a problem that can be more serious.

Inferior nasal coloboma of the iris. Source:
Ming ALS and Constable IJ. Color Atlas of
Ophthalmology, 3rd Ed. Singapore: World
Scientific Publishing Co, 1995:127.

The eyes develop between 4-16 weeks of pregnancy. A coloboma represents a failure of the choroid fissure of the optic cup to close properly.

The optic cup should not be confused with cupping of the optic disc that is a common feature of glaucoma. In this case, optic cup refers to an embryonic structure that forms at about four weeks during gestation from the optic vessicle, the precursor of the eye. The choroid fissure is an open tubular extension that emanates from the optic cup and plays an essential role in the growth of the eye. The choroid fissure forms the route by which developing optic nerve fibers exit the eye and is the means through which blood vessels enter the eye. At week 6-7 of gestation, the rims of the choroid fissure normally fuse to form a closed tubular structure. Colobomas result, if the choroid fissure does not close.

The fundus of the eye is the interior surface of the eye that is opposite the lens. The fundus consists of the the retina, optic disc, macula and fovea, Bruch's membrane and the choroid. A coloboma may affect only the front of the eye if fusion of the choroid fissure mostly is complete. On the other hand, it may affect the eye from the front all the way back to the fundus if more of the choroid fissure has failed to close.

The most common form of coloboma affects the iris. This apparently is the type that your daughter has in her right eye, as the fundus does not appear to be involved. Children with this type of coloboma often have fairly good vision. The pupil of the eye is misshapen, like you describe, and looks somewhat like an old-fashioned keyhole. Affected children also may have some degree of photophobia (sensitivity to bright light) because the iris, which controls the amount of light entering the eye by changing the size of the pupil, may not function properly. Too much light entering the eye can cause discomfort and image distortion. You can take measures to help protect your daughter from bright light by using curtains or blinds on windows, low watt light bulbs, hats with visors, sunblinds in cars, and sunglasses (when she is older).

When the coloboma extends back into the fundus, the child may have more visual problems, especially if the retina or optic nerve is involved. In this instance, central vision can be affected. Central vision is used for detailed activities such as reading, writing and close work or play.

Colobomas can be associated with other eye problems. Among these are microcornea, which refers to a cornea that is 10 mm or less, microphthalmos, in which the eyeball is smaller than normal, and microphthalmos with a cyst. When a coloboma is associated with microphthalmos or microcornea, it is likely that the uvea and retina are involved. This means that vision can be affected significantly.

In rare instances, children can have CHARGE syndrome. This is an acronym that stands for:

Coloboma
Heart defects
Atresia of the choanae (problems with the nose passages)
Retarded growth and development
Genital hypoplasia (undescended testicles)
Ear abnormalities.

CHARGE syndrome is a genetic disorder that is associated with a mutation in the CHD7 gene located on chromosome 8. CHARGE syndrome is the leading cause of congenital deaf-blindness. However, advances in medical care have enabled children with CHARGE syndrome to become healthy and happy individuals. Appropriate therapies and educational intervention for individuals with CHARGE syndrome must take into consideration hearing impairment, vision problems, and any other medical conditions that are present. Early intervention, such as occupational and physical therapy, is very important as the intelligence of children with multiple health issues such as combined deaf-blindness often is underestimated. Because of the developmental delay in CHARGE syndrome, early intervention can play an important role in promoting mobility, improving static postures, transitioning towards ambulation, and teaching self-care skills. When possible, clinical management of CHARGE syndrome should involve a multidisciplinary team that is coordinated by a single person.

Studies have been conducted to determine the degree of visual acuity in children with coloboma. Findings indicate that if the defect is simple, involving only the iris, and no other abnormalities of the eye are present, visual acuity is 6/18 or better (20/20 is normal visual acuity). If there is an associated abnormality, such as microcornea, visual acuity is lower. When the eye also is abnormally small (microphthalmos), visual acuity is from very low to no light perception in 67% of children.

There is no effective treatment able to restore congenital ocular abnormalities, such as coloboma, to good visual acuity. Children with colobomas usually receive specialist care during their early years to monitor the impact of the coloboma on eye health. The frequency of care depends upon individual needs. Affected children can be at greater risk for glaucoma (elevated eye pressure) and retinal detachment. Treatments exist for both of these conditions, which a specialist will explore with you. If no further complications emerge, then an ophthalmologist usually will perform eye examinations at six month intervals up to the age of seven years, followed by annual exams.

It is important to be active in your daughter's care. Work with specialists to thoroughly understand her condition. Be a strong advocate for your daughter in order to ensure that she has access to an educational program that will allow her to reach her full potential. Children with colobomas vary greatly in their abilities in the classroom. Some require very little support, while others may need full-time support and individualized programs.

Carolina Valdivia, MD

REFERENCE:

Lueder GT. Pediatric Practice Ophthalmology. New York: McGraw Hill Medical, 2011:202.

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