When the eye is developing, the fetal neural eye structure wraps around and joins together in what will become the bottom of the eye. If the two sides do not combine completely there can be gap in the iris (the colored part of the eye) called a coloboma which produces a keyhole-like appearance in the pupil. This incomplete closure can also affect the layers of the back of the eye (choroid and retina) and the optic nerve. The disorder can occur in one or both eyes. It is estimated that coloboma occur in 0.5 to 0.7 per 10,000 births.
Vision loss from Colobomas may vary from mild to severe depending upon its size and location. Occasionally other ocular malformations or disorders may be associated with coloboma including microphthalmia (a very small eye), glaucoma, nystagmus,strabismus (turned eyes), or blind spots in the visual field.
Low Vision Treatment
While there is no medical or surgical treatment available to treat the disorder, low vision care can often provide significant functional gains for the individual. Generally, magnification and illumination control are used to enhance visual functioning for individuals with colobomas.
Proper lighting that increases contrast but reduces glare can be very helpful in many circumstances. Specially tinted wrap-around sunglasses that reduce brightness but increase contrast are often helpful out of doors. These are also available in versions that fitover prescription eyewear that may also be required.
Conventional eyeglasses, while maximizing the focus on the back of the eye, may not provide adequate vision for seeing at a distance. The only options are to move close or to use telescopic devices to bring things closer optically. Telescopic devices can be either handheld or spectacle mounted (bioptics). They can be very helpful to improve distance vision for TV, signs, the classroom, recognizing faces and social engagement, and even for driving.
Special Artificial Iris Contact Lenses
In addition to the range of magnifying devices available for the visually impaired, special contact lenses with an artificial iris can produce a normally sized pupil that can help make vision sharper and reduce glare and light sensitivity.