Aniridia is a rare condition where the iris (the coloured part of your eye) has not formed properly, so it may be missing or underdeveloped.
The word “aniridia” means “no iris”, but the amount of iris tissue missing will vary from person to person. People with aniridia will often have very large pupils (the hole in the middle of each iris) which may also have an irregular shape because so much of their iris tissue is missing. Some people with aniridia may have more regular looking iris and the changes are only visible to an eye specialist.
Most people with aniridia have a central part of their retina that is not fully developed, and many have nystagmus, a constant and involuntary movement of the eyes.
Aniridia affects both eyes and it is a condition which you’re born with.
Our downloadable factsheet has more information about aniridia:
Below is a summary of information from our guide.
Aniridia is a genetic condition, which means it is caused by a mutation, or fault, in a gene. In the majority of cases, aniridia is caused by a fault in the PAX6 gene, although in a small number of cases another gene might be responsible.
All genes come in pairs. You inherit one copy of the gene from each of your parents to make a pair. Your genes give the cells in your body the instructions they need to work well and stay healthy. When a gene is faulty, the genes do not give their instructions correctly to the cells and the cells then don’t develop or work as they should.
There are two ways in which aniridia can be inherited from a parent:
People with aniridia aren’t able to control the amount of light entering their eyes because their iris tissue is missing, their pupils remain large and their eyes do not adjust to differing lighting levels. People with aniridia can therefore experience dazzle, particularly in bright conditions, or difficulty adjusting as light levels change, reducing vision. As well as having an impact on sight, the light sensitivity (photophobia) they experience can cause discomfort and can, for some people, cause headaches.
Aniridia nearly always causes other parts of the eye to be underdeveloped, such as the optic nerve and fovea, and can also cause nystagmus. These conditions can also affect vision in addition to the lack of iris. People with aniridia may also develop other eye conditions, such as glaucoma, cataract and corneal problems. These other effects on the eye can have a larger impact on sight than the large pupil or lack of iris itself.
Aniridia and these associated conditions affect everyone differently. So, while some people with aniridia have quite a lot of sight loss, others may have only mild blurred vision.
Other eye conditions can be linked with aniridia, some of which can be present from birth and some which may develop later on in life. Not everyone with aniridia will experience all these eye conditions.
The following eye conditions can be linked to aniridia:
Nystagmus is constant and involuntary movement of the eyes. This uncontrolled movement can affect how clearly a person can see and is likely to reduce their vision. Nystagmus is usually present from birth or very soon after birth.
People with aniridia often have foveal or optic nerve hypoplasia. “Hypoplasia” is a term that refers to underdevelopment of tissue and is a condition someone is born with. The degree of “underdevelopment” can vary between different people, so how much it affects someone’s sight can vary.
People with aniridia can develop cataract at an early age, often in late childhood or adolescence or early adulthood. A cataract is a clouding of the lens and this will cause sight to become cloudy and misty. Cataract may only affect a small part of the lens but if it starts to affect vision a lot, it may require treatment. Cataracts can be safely left untreated for many years if the vision is not badly affected.
Glaucoma is an eye condition where your optic nerve is damaged by the pressure of fluid inside your eye. Glaucoma in people with aniridia can develop in late childhood, adolescence or early adulthood. Treatment for glaucoma can be given to lower eye pressure and to prevent damage to the optic nerve and to protect sight.
Keratopathy simply means an unhealthy cornea. Signs of keratopathy can start anytime from childhood onwards but tends to occur more as people move into adulthood and middle age. Keratopathy usually starts as a ring of clouding around the edge of the cornea, but if it progresses into the centre of the cornea then vision can become hazy or blurry. Keratopathy can make the eye feel dry and uncomfortable, and lubricating eye drops may help with this.
Unfortunately, there is no treatment to cure aniridia at the moment.
There are treatments available for some of the eye conditions associated with aniridia, such as cataracts, glaucoma or keratopathy.
Children and adults with aniridia will usually be monitored by an ophthalmologist (hospital eye doctor) regularly throughout life. This is to ensure that their eye health is monitored for other eye conditions associated with aniridia.
Although glasses and contact lenses cannot improve any sight problems that are caused by aniridia, it’s important for children to have any focusing problems corrected to allow their sight to develop as fully as possible.
People who are light sensitive find that bright light causes discomfort. The level of discomfort can vary from person to person. Although there is no one solution for light sensitivity, many people with aniridia find that shielding their eyes with sun hats, sunglasses or tinted glasses, or sun blinds in cars can help. More information about coping with light sensitivity can be found on our light sensitivity page.
Download our factsheet for our full information on aniridia and for more information on help and support available.