Aniridia

What is aniridia?

Aniridia is a rare eye condition that you’re born with. It happens when the coloured part of your eye – the iris – doesn’t develop properly. The word aniridia literally means ‘no iris’[1].

You might also hear it called: congenital aniridia, aniridia syndrome or sometimes irideremia or absent iris.

What causes aniridia?

Broadly, there are two main causes of aniridia: genetic, and resulting from a wider syndrome.

What are the genetic causes of aniridia?

The commonest cause of aniridia is genetic [2] and it is a gene that some people are born with. It’s caused by a ‘spelling mistake’ (pathogenic variant*) in a gene that’s essential for eye development.

The main gene linked to aniridia is called PAX6. This gene acts as a ‘master controller’ for how the eyes, brain, spinal cord, and pancreas develop when a baby is growing. Everyone has two copies of the PAX6 gene, but a mutation in just one of them can cause aniridia.

There are many different variants in the PAX6 gene that can cause aniridia. This helps explain why the condition can be so different from one person to the next. In very rare cases, conditions that look like aniridia can be caused by mutations in other genes.

*Pathogenic variant or commonly known as “mutation”.

Is aniridia inherited from a parent?

Yes, about two out of three times, aniridia is passed down from a parent. It’s usually passed on in a way that means a child of someone with aniridia has a 50/50 chance of having the condition too (it is autosomal dominant [3]).

But aniridia isn't always passed down from a parent.

For about one in three people [4], the condition is caused by a new gene variation that happens by chance. This is called sporadic aniridia, and it means there’s no family history of the condition. If you have sporadic aniridia, you can still pass the condition on to your children.

When is aniridia part of a wider syndrome?

Some people with aniridia, especially if the condition is not inherited, have it as part of a wider syndrome.   Examples include WAGR syndrome and Gillespie Syndrome.

What is WAGR syndrome and how does it impact the eye?

WAGR syndrome is a genetic condition that causes a range of issues around the body. WAGR is an acronym that stands for the main health problems it can cause: Wilms’ tumour, Aniridia, Genitourinary problems, and a Range of developmental delays.

Aniridia is often the first and most obvious sign of the syndrome.

The condition is caused by a piece of genetic material being accidentally deleted from chromosome 11.

This missing piece includes the PAX6 gene, which causes the aniridia, and another gene called WT1. The loss of the WT1 gene leads to a high risk of developing a type of kidney cancer called Wilms’ tumour and problems with how the reproductive organs and urinary tract are formed.

Most cases of WAGR syndrome are not passed down through families but happen by chance before birth.

Between 13% and 30% of people with aniridia have WAGR syndrome. [5][6].  

What is Gillespie syndrome and how can it impact the eye?

Gillespie syndrome is an extremely rare genetic condition affecting the eyes and muscle coordination. It’s so rare that fewer than 100 cases have ever been identified.[7][8] The main signs are aniridia, problems with balance and coordination (known as ataxia), and some level of learning disability.

It’s caused by a mutation in the ITPR1 gene. People with Gillespie syndrome usually have an unsteady walk, difficulties with speech, and weak muscles from birth. The partial aniridia seen in this syndrome looks a bit different, with an unusual wavy or scalloped edge to the iris.

What are the signs and symptoms of aniridia?

You can often see signs of aniridia shortly after a baby is born.[9]

The most obvious sign is how the eyes look. The iris is partly or almost completely missing, which makes the pupils look very big or an unusual shape.[10]

People with aniridia may experience the following symptoms:

• Light sensitivity (photophobia): The underdeveloped iris can’t constrict to reduce the amount of light getting into the eye, so bright lights may cause discomfort.
• Reduced vision: Vision is often less clear because a key part of the retina (the light-sensitive layer at the back of the eye) used for sharp, central vision isn't fully developed.
• Difficulty focusing: Many people with aniridia also need glasses for common problems like short-sightedness.
• A sore eye: The clear front surface of the eye can get dry and become easily damaged. This can be painful and make vision even blurrier.
• Hazy or blurry vision: This can be caused by a few things, including cataracts and a cloudy cornea, which can both develop over time.

What are the physical signs associated with aniridia?

Common signs of aniridia, include:

• Nystagmus: This is when the eyes move or ‘wobble’ with rapid, uncontrollable movements.
• A squint (strabismus): This is when the eyes point in different directions.
• Drooping eyelids (ptosis): This can be caused by the same genetic changes that lead to aniridia but doesn’t affect everyone with aniridia.

How does aniridia affect your vision?

How much someone with aniridia can see varies widely, from near-normal to certified vision-impaired or severely vision-impaired. The first thing people usually notice is strong sensitivity to light (photophobia). 
This is because the missing iris can’t control how much light gets into the eye.

Most people with aniridia have reduced visual acuity. It’s harder for them to see things clearly and sharply. This is often because the central part of the retina (the light-sensitive film at the back of the eye) is underdeveloped. Some people describe it as looking like a low-resolution photo. 

The rapid eye movements of nystagmus also make it harder to focus.

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What is the impact of aniridia?

How aniridia affects someone can vary a lot, but it will always have some impact on vision. The biggest risks to sight are from glaucoma, which is linked with aniridia (see below) and from the cornea and lens becoming cloudy, which stops light from reaching the back of the eye.

People with aniridia may become certified as vision impaired or severely vision impaired. It can also cause problems in the whole eye. This can lead to other eye conditions developing later in life, which can seriously affect vision.

How is aniridia diagnosed?

An eye specialist (an ophthalmologist) will usually diagnose aniridia by examining a baby’s eyes at birth or soon after. The most obvious sign they look for is a missing or partially missing iris. The specialist will also look for other typical signs, like nystagmus, and check for early signs of linked problems like cataracts or glaucoma.

Genetic testing is often offered to confirm the diagnosis and understand more about the specific gene variation. This test looks for mutations in the PAX6 gene. 

It’s especially important for children who are the first in their family to have aniridia. This is in case it’s caused by WAGR syndrome, which brings a higher risk of a type of childhood kidney cancer. Children with WAGR syndrome are given regular kidney scans to check for a tumour. [11]

What other eye conditions are linked to aniridia?

Several other eye problems are linked to aniridia. Some can be there from birth, while others can develop as you get older. These developing conditions are often the main reason for serious sight loss.

• Amblyopia: Also known as a ‘lazy eye’, this can happen in people with aniridia. If it does, it needs to be treated quickly to help the vision develop as well as it can.
• Cataracts: This is when the lens of the eye becomes cloudy. It affects more than half of people with aniridia and often happens much earlier in life than usual age-related cataracts. If a cataract makes vision worse, it can be removed with surgery.
• Glaucoma: This is one of the most common and serious linked conditions. It affects about half to three-quarters of people with aniridia and usually develops in late childhood or as a young adult. Glaucoma is caused by high pressure inside the eye, which can damage the optic nerve (the cable connecting the eye to the brain) if it's not treated.
• Foveal hypoplasia: Foveal hypoplasia is the underdevelopment of the eye's fovea and commonly occurs in aniridia (the absence of the iris). The combination can lead to reduced visual acuity and nystagmus (involuntary eye movements).
• Keratopathy: Aniridia-associated keratopathy (AAK) is a problem that gets worse over time. The cornea (the clear window at the front of the eye) gets cloudy, scarred and can have blood vessels grow across it. This happens because there aren't enough special stem cells to keep the cornea healthy and clear. AAK often starts in childhood but might not affect sight until you’re an adult.
• Nystagmus: This is constant, rapid eye movements and is very common for people with aniridia and usually start very early in life. It’s thought to happen because the messages between the underdeveloped eye and the brain don’t work as they should.
• Optic nerve hypoplasia: For about one in ten people with aniridia [12], the optic nerve which sends signals from the eye to the brain is underdeveloped (hypoplasia means ‘underdevelopment’). Depending on the severity, this might cause mild or severe vision problems. This problem doesn’t get any worse over time, but it does affect the level of vision a person has from the start.

What are the treatments for aniridia?

There is currently no cure for aniridia. It isn't possible to regrow a missing iris or fix the way the eye developed. Instead, treatment focuses on managing symptoms and addressing any associated eye conditions. The aim is always to protect sight and make the most of the vision a person has.

A team of eye care professionals, including specialist eye doctors (ophthalmologists) and optometrists, will help manage the condition.

Treating linked conditions: This is a very important part of ongoing care.

• Glaucoma: This can be tricky to treat. It often starts with eye drops to lower the pressure in the eye. Many people will eventually need an operation to control the pressure properly.
• Cataracts: If a cataract gets in the way of seeing, it can be removed with surgery.
• Keratopathy: The first step is usually using artificial tears to keep the eye's surface moist. If it gets worse, an operation to transplant special stem cells may be needed to help the cornea heal and stay healthy.
• Glasses and contact lenses: Standard glasses and contact lenses can't fix the sight problems caused by the underdeveloped parts of the eye. But they are still important for correcting things like short-sightedness. Special cosmetic contact lenses with a coloured iris and fixed pupil can also help. They can reduce light sensitivity and can also make the eye look more typical.

Although several types of artificial iris have been developed, they are not commonly used outside of research, because of the risk of damaging the eyesight.[13]

What can help aniridia?

Living well with aniridia involves a mix of regular medical care and practical things to help with vision day-to-day.

• Regular eye checks: It’s essential to have lifelong, regular appointments with an eye doctor. This helps to spot and treat problems like glaucoma and keratopathy early, before they cause serious sight loss.
• Sunglasses and tinted lenses: Because of the strong light sensitivity, good quality sunglasses that block UV light are essential for being comfortable outdoors. Wearing a wide-brimmed hat helps too. Some people also find that lightly tinted glasses help reduce glare indoors.
• Low vision aids: When sight is significantly affected, low vision aids can make a huge difference. These can be anything from magnifiers to digital devices like tablets or video magnifiers that make text and images bigger and easier to see.

What research is there into aniridia?

Research into aniridia is focusing on understanding the complicated role of the PAX6 gene and finding ways to treat the most damaging parts of the condition.

In 2025, Fight for Sight awarded a Project Grant to Dr Kevin Hamill, who is researching a potential gene therapy for aniridia.

Dr Hamill is leading a project looking at how to treat the damage to the cornea that is a key part of aniridia at the University of Liverpool. Treatments like corneal transplants often don’t work in the long term. This is because the special stem cells needed to keep the new cornea healthy don't work properly in people with aniridia.

• Discover more about the development of artificial corneas in our webinar

This research hopes to use a new type of therapy called self-amplifying RNA (saRNA) to fix the root cause of the problem. This clever technology gives instructions to the eye's cells, telling them to make more of the important PAX6 protein. This helps to correct the genetic problem. This therapy can also make copies of itself once it's inside the cells, which means smaller and possibly safer amounts can be used.

The team has created this technology and will test it as an eye drop on mice that have the condition. The aim is to see if this method can stop or slow down the corneal disease.

If it works, this project could lead to studies in people. The long-term hope is to create a simple eye drop that people could use to stop the painful corneal problems from getting worse. This would protect their sight and mean they wouldn't need to have repeated, difficult operations.

Read more about Dr Hamill’s research into aniridia

Identifying drugs that could reduce sight loss

Professor Jon Collinson was awarded a Fight for Sight Small Grant Award in 2019 to see whether certain existing drugs could increase levels of PAX6. The project, which ended in 2021, highlighted two drugs that have the potential to treat corneal disease in aniridia.

The team used mice with mutations in PAX6 as a model of aniridia to test these drugs. Both of the drugs tested demonstrated safety and effectiveness in the mice. They are both drugs which are already approved for other conditions but happen to have an effect on PAX6. Given that the drugs increase levels of PAX6, in theory they could work for all cases of aniridia, regardless of the type of mutation. Research into the use of these drugs for treating aniridia is still ongoing.

Read more about Professor Collinson’s work