Coloboma

Coloboma is a condition that occurs when a specific portion of tissue is missing inside or around the eye. Six types of coloboma exist.

Causes & risk factors

A coloboma is a condition that occurs when tissue is missing from inside or around the eye. At birth, colobomas can impact both eyes or just one and the type depends on where in the eye the coloboma is. The six different types of colobomas include:

• Chorioretinal colobomas occur when part of the retina is missing. The retina is the layer of cells lining the back of the eye that senses light and sends nerve signals to the brain.
• Eyelid colobomas occur when a portion of the upper or lower eyelid is missing.
• Lens colobomas occur when a piece of the lens is missing. The crystalline lens is located behind the iris and helps focus light.
• Macular colobomas occur when the macula fails to develop properly. The macula is a small area in the center of the retina that focuses on details.
• Optic nerve colobomas occur when the optic nerve is hollowed out. The optic nerve connects your eye to your brain. Optic nerve colobomas often result in reduced vision.
• Uveal colobomas occur when part of the middle layer of the eye is missing. The uvea is made up of the iris, choroid, and ciliary body. This type is most cosmetically apparent.

Symptoms

Colobomas are present at birth and some symptoms may not be apparent right away. The most obvious symptom of a coloboma is a keyhole-shaped pupil common in uveal colobomas. Other symptoms of colobomas can include:

• Low or poor vision
• Blindness or vision loss
• Sensitivity to light
• Inability to control eye movements (nystagmus)
• Reduced peripheral vision
• Issues with depth perception
• Blind spots in field of vision

Diagnosis

A doctor of optometry can examine an infant to determine if any abnormalities are present and assess the extent of the damage.

Treatment

Currently, no cures exist for any colobomas. Your doctor of optometry may prescribe or recommend options to help retain as much vision as possible. Some options include:

• Surgery to fix the appearance of the iris
• Colored contact lenses to fix the appearance of the iris
• Surgical procedures to fix an eyelid coloboma
• Corrective lenses such as glasses or contact lenses
• Low-vision aids like magnifiers and screen readers

For coloboma in only one eye, optometrists might provide tools to help prevent amblyopia, also known as “lazy eye.” Treatment for amblyopia may include eye drops, patching, and or vision therapy. 

Prevention

There is evidence colobomas are genetic, however scientists haven’t determined which genes cause colobomas. Therefore, there is no prevention available yet.