About MACS Conditions

Image shows child with bilateral anophthalmia
Image shows child with unilateral microphthalmia
Image shows child with unilateral coloboma

We support children and adults who have one of, or sometimes a combination of, three eye conditions: Microphthalmia, Anophthalmia and Coloboma.

Some people with a MACS condition are blind, others have a degree of light perception, and some may be blind in one eye with some, or even good, sight in the other eye. The conditions develop during pregnancy and are often associated with other congenital (present at birth) disorders such as endocrine or heart problems. Some people with a MACS condition also have learning and developmental difficulties and behavioural problems.

Around 80-90 children are born with a MACS condition in the UK every year.

​Microphthalmia: Microphthalmia literally means 'small eye'. Children may be born with one, or both eyes, small and underdeveloped. Some children may be blind, but others may have some residual sight or light perception.

Anophthalmia: Anophthalmia means an absence of the eye. As with Microphthalmia, a child may be born with one, or both eyes, missing from the eye socket.

Coloboma: Coloboma means that there is a gap or cleft in one of the structures of the eye. Vision may or may not be affected depending on the part of the eye that is involved.

If you would like information on prosthetic eyes please click here.


We don't yet know exactly why Microphthalmia and Anophthalmia occur, but they are likely due to a disruption in the sequence of developmental steps that take place when the eye is forming during pregnancy. This could be as a result of an error within specific genes affecting eye development and increasingly, more genes are being identified as important in the development of these conditions.

External factors may influence the function of those genes and the conditions have been related to illness experienced during pregnancy such as chicken pox and rubella, or drugs such as thalidomide. Environmental factors such as insecticides and fungicides have also been linked to the development of the conditions.

Coloboma occurs as a result of congenital malformation, with a portion of the eye failing to complete its growth very early in pregnancy.

Treatment: There is no treatment that will restore vision in children affected by Anophthalmia or severe Microphthalmia. All MACS children need to undergo repeated hospital visits and many have prosthetic eyes to ensure that the bone and soft tissue around the eye socket grows properly and to improve appearance.