What are the different kinds of coloboma?

There are different kinds of coloboma, depending on which part of the eye is missing. Coloboma can affect the eyelid, lens, macula, optic nerve, or uvea.

Eyelid coloboma
In eyelid coloboma, a piece of either the upper or lower eyelid is absent. Eyelid coloboma may be part of a genetic syndrome or happen as a result of a disruption of eyelid development in a baby. A syndrome is a specific grouping of birth defects or symptoms present in one person.

Lens coloboma
In this type of coloboma, a piece of the lens is absent. The lens, which helps focus light on the retina, typically appears with a notch.

Macular coloboma
This happens when the center of the retina, called the macula, does not develop normally. The macula is responsible for daylight, fine, and color vision. Macular coloboma may be caused when normal eye development is interrupted or when the retina is inflamed during the development of the baby.

Optic nerve coloboma
Optic nerve coloboma refers to one of two distinct things:

An abnormal optic nerve that is deeply "excavated" or hollowed out. In some cases, it can also be referred to as an optic nerve pit. The optic nerve is a bundle of nerve fibers that relays light signals from the eye to the brain. An uveal coloboma that is large enough to involve the optic nerve, either the inferior portion or the entire optic disc.

This answer is based on source informationfrom the National Institute of Diabetes and Digestive and Kidney Diseases.