Anophthalmia occurs when one or both eyes of a person are missing when they are born. The eye has essentially failed to develop within the first few weeks of pregnancy. The affected side has no vision. If only one eye has Anophthalmia, a person may have full, or partial vision in the other eye depending on whether it has developed normally, or, if it's affected by being particularly small and underdeveloped, which is called Microphthalmia, or, have a gap within the eyeball known as Ocular Coloboma. These associated conditions are often seen together and are collectively called MAC conditions standing for Microphthalmia, Anophthalmia and Coloboma. Only one in 30,000 people are born with Anophthalmia, making it an extremely rare condition.

The eye first starts to develop after three weeks of pregnancy, the eye grows out from the brain as a sphere attached by a stalk. The sphere becomes the eyeball and the stalk becomes a nerve, connecting the eye to the brain. By day 30, a cleft forms on the underside of the eyeball to allow blood vessels to grow into the eye and supply it with nutrients. This cleft then fuses, allowing the globe of the eye to be formed. For the eye to form properly a specific set of genes must be switched on, at the right time, in the right place, during development.

Changes in our genetic code, also known as our DNA, and the environment within the womb, can prevent genes being switched on or off at the correct time in eye development. Environmental factors can include infections during pregnancy like Rubella, or if the mother is deficient in vitamin A but these only cause roughly two percent of MAC conditions. Most people with Anophthalmia will have a change in their DNA which prevents the correct instructions for the eye to form.  Changes in over 100 different genes are known to cause MAC conditions.

To find out the genetic cause of Anophthalmia, we can perform genetic testing. We usually do this by taking a blood sample, and extracting the DNA, so we can look for any changes in genes we know cause the condition. At the moment we can only find a genetic cause in around one in five patients with MAC. This is mainly because we haven't discovered all the genes that cause the condition yet. We have three billion letters in our genetic code and twenty thousand genes. We all naturally have around three to four million genetic changes that makes us individuals, 10,000 of these can be potentially disease causing, so finding the exact genetic cause can be challenging, and needs an expert team. We're trying to find more genetic causes of MAC so that we can let more families know how their condition was caused. We're now able to read the full genetic code of a patient using a technique called whole genome sequencing and this will really help improve diagnostic rates for patients.

By understanding how the different genetic causes of MAC we can hope to better understand how the eye forms and how faulty genes impact eye development as well as development of other parts of the body. This knowledge allows us to assemble the correct multi-disciplinary team to support patient care, and provide families with information on family decision making. Ultimately we hope that all this work in understanding the genes involved in MAC, will lead us to developing potentially preventative treatments.

Receiving a diagnosis of Anophthalmia, as a parent, can have a huge impact on the family MACS Charity can support you through this time. If you need more information on the condition, the latest research, support available and genetic eye disease specialists around the UK, then please refer to the Gene Vision website at www.gene.vision and we would be more than happy to see you at Moorfields Eye Hospital.