A coloboma is a congenital or acquired defect that affects a part of the eye or eyelid. The condition can refer to an underdeveloped eyelid, a hole in the iris, a missing section of the lens, or a deeper defect in the optic nerve. The signs and symptoms depend on what part of the eye is affected, but many people experience some degree of blurred or distorted vision. Doctors are usually unable to correct the actual defect, so treatment generally involves lessening symptoms with corrective glasses and anti-inflammatory medications.
Most colobomas are present at birth due to genetic mutations, prematurity, or fetal injury. In some cases, a coloboma can arise later in life following surgery or direct trauma to the eye. The most common site of the deformity is the iris, the colored circle of tissue that surrounds the pupil. A gap or tear in the iris can create a black patch connected to or near the pupil. Commonly referred to as cat's eye syndrome, an iris coloboma can cause light sensitivity and double vision.
Colobomas can also form on the lens, retina, or optic nerve. Such a defect usually cannot be detected by looking at the eye, but it may cause a number of vision problems. Blurred sight, poor peripheral vision, and eye irritation and redness are common. Rarely, a deep or large coloboma can cause blindness. Eyelid colobomas, where part of the upper or lower eyelid does not fully form, can leave the eye susceptible to chronic dryness and frequent infections.
Whenever an infant or an older patient exhibits the physical symptoms of a coloboma, he or she is referred to an ophthalmologist for a careful examination. The doctor can peer into the eye with a specialized type of microscope to inspect the deformity. He or she also conducts a series of sight tests to determine how much the coloboma affects vision acuity and light sensitivity. Additional diagnostic screening tests may be performed to check for signs of underlying health problems and other types of defects.
Treatment for a coloboma depends on its location and the severity of symptoms it causes. In many cases, patients simply need to use soothing eye drops and attend regular checkups with their ophthalmologist. Protective sunglasses may be needed if an eye is especially sensitive to light, and prescription glasses or contacts can help to improve vision problems. Eyelid colobomas can often be corrected with a relatively straightforward surgical procedure. Surgery has not proven safe or effective, however, at treating colobomas within the actual eye structure.