The Dr. Bill Takeshita Foundation

Last Modified: Sat, 18 Aug 2007

View other Common Causes of Vision Impairment

A coloboma is the incomplete development of one or more structures of the eye. This abnormal development occurs in the growing fetus and does not change after birth. Colobomas are similar to a cleft where the tissues have not fused together, resulting in a gap or hole in the structure of the eye. It is a congenital condition that may affect the eyelid, retina, choroid, optic nerve, and various parts of the body. Consequently, many patients with coloboma have cleft palates or cardiac septal defects (holes in their hearts). The severity of the coloboma determines the degree of functional vision. Many patients have small coloboma that only affect one region of the eye. These patients may have a very high degree of vision. In contrast, the birth defect may prevent the formation of the entire eye the eye may be extremely small (microphthalmia) or the eye may not develop at all (anophthalmos). For those with microphthalmia and anophthalmia, the level of vision is often very poor. There are no medical treatments to repair the undeveloped tissues of the eye but many patients respond extremely well to optometric low vision aids and cosmetic contact lenses.

Iris coloboma is when a section of the iris is not developed normally. Iris Colobomas generally involves the lower portion of the iris, resulting in a pupil that resembles a keyhole of an old-fashioned door lock or the pupil may appear oval rather than round. The iris regulates the amount of light that enters the eye and also gives the eyes their eye color. Colobomas of the iris generally do not cause blurred sight but they may cause mild sensitivity to glare and bright light. Cosmetic contact lenses can be fit to improve the cosmetic appearance of the iris.

Eyelid colobomas can cause visual and cosmetic problems for newborn children. The absence of part of the eyelid interferes with the manner in which tears wash and lubricate the eyes. As the front of the eye dries out, the cornea can become clouded or opaque. This hinders the manner that light enters the eye, causing blurred sight, glare, distorted vision, and sensitivity to glare. Contact lenses and artificial tears can keep the cornea moist until surgery can be performed to repair the eyelid.

Choroidal and retinal colobomas generally occur simultaneously and cause the loss of peripheral vision in the upper field and blurred sight. The choroid is a vascular tissue that supplies blood and oxygen to the light sensing tissue called the retina. When the choroid is not fully developed, the cells of the retina do not develop and that region of the eye is blind. Choroidal and retinal colobomas generally affect the lower retina, which provides us with our upper peripheral vision. Choroidal colobomas may also extend to the central retina and affect the macular region of the retina where detailed vision occurs. When the coloboma extends to the macular region, the visual acuity may be as poor as 20/400 (able to read a 7 inch letter from a distance of twenty feet). These patients often have difficulty reading street signs, small print, and they may bump into objects that are above their head. Patients with choroidal colobomas are at risk for developing retinal detachments and should be seen by a retinal specialist each year.

Colobomas may also involve the optic nerve and are called optic nerve colobomas. The lower portion of the optic nerve is typically the affected region and this can result in the loss of peripheral vision in the upper field as well as blurred sight, ranging from 20/100 to 20/400. Color vision may also be affected in cases of optic nerve coloboma. Their symptoms are similar to those of patients with choroidal/retinal colobomas. Fortunately, patients with colobomas to the retina, choroids, and optic nerve often respond very well to low vision aids.

Microphthalmia is the term used to describe the partial development of the entire eye. In contrast to a coloboma where only one section of the eye is not fully developed, microphthalmia affects the entire eye and the eye can be thought of as a miniature eye. Microphthalmia can affect one or both eyes and is often inherited. Vision may range from total blindness to the ability to perceive motion and high contrast. Unfortunately, there is no medical treatment for microphthalmia but some patients respond favorably to low vision aids and computer technology.

Anophthalmia is the condition where the eye does not develop during fetal development. In most cases, the eye did not develop at all and there are no eye structures present at birth. In other cases, the eye began to develop but stopped and there are no functional tissues of the eye to support vision. Children with anophthalmos are fit with prosthetic eyes to improve the cosmetic appearance of the eyes as well as to ensure the normal growth of the orbit (eye socket). Without the prosthetic eye, the bones that form the orbit will “sink inward,” affecting the structure of the face.

Patients with coloboma are at risk for other medical conditions. The incomplete development of the eye can also extend downward to other structures of the face, mouth, heart, and body. Many children with coloboma have cleft palates, incomplete closure to the septum of the heart, abnormalities to the fingers, and developmental delays. C.H.A.R.G.E. syndrome describes a congenital disorder that affects the eyes, heart, throat, genital urinary tract, and ears. The letters CHARGE are acronyms to describe Coloboma of the eye Heart defects, including abnormalities to the aorta, Atresia of the choane (abnormal connect from the back of the throat to the nasal cavity), Retardation of development and growth, Genital-urinary abnormalities (undescended testes in males and small genitalia, kidney and urinary problems), and Ear and hearing abnormalities that may cause severe hearing impairment. In as many as 80 percent of cases, children have severe hearing impairment and cardiac problems.

Recommendations

• Adults and children with coloboma often respond very well to low vision aids. A consultation by a low vision specialist and low vision aids are recommended.
• Infants will benefit from vision stimulation to maximally develop the visual cortex of the brain. For specific details, please see Developing Your Child’s Vision.
• Patients with iris colobomas often benefit from wearing specialized filters to reduce problems with glare. Transitions photochromic lenses, Melanin filters, polarized filters, and tinted contact lenses are often very helpful.
• Low vision aids such as bioptic glasses, hand held telescopes, and video magnification systems can improve distance sight to 20/20, while specialized reading glasses, hand magnifiers, and closed circuit televisions can allow patients to read small print, read medication labels, and see photographs. For more details, see Low Vision specialist and low vision aids.
• Students will benefit from being positioned in the front portion of the class with their backs facing windows, doors, and glare sources. The use of a black chalkboard and bold architecture chalk are generally easier to see than dry erase boards due to the glare created by the white board. In the event that a dry erase board must be used, it is very helpful to only use bold black dry erase markers rather than colored markers.
• Tinted paper with bold lines, bold felt pens, and thick pencils will help students to perform writing tasks at school. Students who are bothered by glare will also benefit from placing their paper on a dark blotter or dark piece of construction paper to help them to see the edges of their paper.
• Students will benefit from having copies of material normally written on the board or presented on overhead transparencies. If PowerPoint presentations are used, a dark background with white letters written in Arial or Tahoma will improve readability for students with low vision.
• Many children with coloboma will have difficulty seeing a baseball, tennis ball, or other flying objects while playing sports.
• The use of incandescent light bulbs hidden behind a dark torchierre floor lamp can provide excellent general lighting while reducing glare. A small desk lamp such as an OTT full spectrum lamp may provide a soft light for reading and writing. See Lighting and Vision for more information.
• Computer users will benefit from changing the background of the display to a black or blue background with white letters. Enlargement of the font size will also increase readability. For information on how to modify the computer screen, see “Solutions To Help You User Your Computer.
• Students may benefit from using specialized computer software and technology such as Zoom Text magnification software, scanning programs such as Open Book and Kurzweil, and Video Magnification systems. For more information, see Computer and Assistive Technology.
• Teenagers with coloboma who are interested in learning whether they have sufficient vision for driving should have a low vision examination by an optometrist who specializes in fitting bioptic-driving glasses.
• Specific low vision aids that are often helpful to patients with coloboma include:
  • Cosmetic contact lenses for patients with iris coloboma
  • 3x to 6x bioptic spectacles
  • Micro spiral telescopes to improve distance sight
  • Aspheric high powered reading glasses
  • Prescription CPF, Transitions, Melanin, and NoIR filters.
  • 4x to 6x aspheric hand magnifiers for reading fine print
  • ZoomText software magnification software for those with coloboma and JAWS screen reading software for those with microphthalmia and anophthalmos.
• For more information, please see Low Vision Rehabilitation