Aniridia

Unfortunately, the exact causes of aniridia are not always fully understood, but most cases are linked to genetic changes that affect how the eye develops before birth:

• Genetics: Most cases of aniridia are caused by a change (mutation) in the PAX6 gene, which plays an important role in the development of the eyes during pregnancy.
• Inheritance: Aniridia can be inherited from a parent. It’s usually passed down in an autosomal dominant pattern, meaning a child has a 50% chance of inheriting the condition if one parent has it.
• Genetic change: In some people, aniridia develops because of a new genetic change that occurs during early development.
• Genetic conditions: In rare cases, aniridia can occur as part of a broader genetic condition, such as WAGR syndrome, which can also affect other parts of the body.
• Pre-birth development: Because the genetic change affects how the eye forms during early development, several structures of the eye may be affected, including the iris, retina, cornea and optic nerve.

Symptoms of aniridia can vary from person to person. The condition is usually present from birth and may affect vision in different ways depending on how the eye has developed.

Common symptoms include:

• Light sensitivity (photophobia): Because the iris is partially or completely missing, more light enters the eye than normal. This can make bright environments uncomfortable causing glare.
• Reduced vision: Many people with aniridia have reduced visual acuity from childhood. Vision may range from mild impairment to more significant sight loss.
• Nystagmus: Some people develop involuntary eye movements, known as nystagmus, which can impact your ability to focus on objects.
• Large pupils: The pupil may appear larger than normal or irregular in shape because the iris has not fully formed.
• Difficulty focusing: Some people may experience problems focusing on objects clearly. 
• Glare and difficulty seeing in bright light: Bright light may make it harder to see clearly because the eye cannot control the amount of light entering it.

Aniridia is usually diagnosed at birth or during early childhood because the iris does not appear fully developed. The condition may be identified during a routine eye examination or when parents notice unusual pupil appearance or visual difficulties. Diagnosis typically involves several tests to assess how the eyes have developed and how vision is affected.

Eye examination: An ophthalmologist will examine the structure of the eye, including the iris, retina and optic nerve, to identify any abnormalities.

Vision tests: Visual acuity tests may be used to measure how clearly a person can see and to determine the level of visual impairment.

Imaging tests: Specialised imaging may be used to examine structures inside the eye, such as the retina or optic nerve.

Genetic testing: In some cases, genetic testing may be recommended to identify changes in the PAX6 ⁴ gene, which is commonly linked to aniridia.

Monitoring for related conditions: Because aniridia can affect several parts of the eye, regular examinations are important to monitor for conditions such as glaucoma, cataracts or corneal problems.

Current treatments:

Although there is currently no cure for aniridia, there are treatments available to help manage symptoms and reduce the risk of complications. Because aniridia can affect several parts of the eye, treatment usually focuses on protecting vision and managing associated eye conditions such as glaucoma, cataracts or corneal problems.

Current treatments may include:

• Glasses or contact lenses
• Medication
• Regular eye examinations

Although treatments can help manage symptoms, many people with aniridia will benefit from ongoing support to manage visual impairment, including advice on living with sight loss and access to low-vision services, including guidance on living with sight loss ² and support groups ³.

Potential treatments:

At Sight Research UK, we are working tirelessly to find solutions to treat AMD. Your eye specialist can let you know if there are any clinical trials you could participate in or you can find an active clinical trial here. Here are just a few of our projects that we’ve been working on with researchers all over the UK:

Have regular eye tests to detect issues early on

Aniridia cannot usually be prevented because it is most often caused by genetic changes that occur before birth. However, early diagnosis and regular monitoring can help detect complications early and protect vision.

People with aniridia should have regular check-ups with an eye specialist to monitor eye health and identify associated conditions such as glaucoma, cataracts or corneal problems as soon as possible.

Learn whether you are at higher risk of developing aniridia

Although aniridia is rare, you may have a higher chance of the condition occurring if you:

• Have a family history of aniridia
• Have a parent with a mutation in the PAX6 gene
• Have a genetic condition associated with aniridia, such as WAGR syndrome
• Have inherited the condition from a parent, as aniridia can be passed down genetically

Families with a history of aniridia may benefit from genetic counselling, which can help explain the risk of passing the condition on to children and provide information about genetic testing.

There are different forms of aniridia depending on how the condition occurs and whether it is inherited or linked to other conditions.

Congenital (isolated) aniridia

Congenital aniridia is the most common form of the condition and is present from birth. It is usually caused by a mutation in the PAX6 gene, which plays an important role in the development of the eyes before birth.

People with congenital aniridia typically have partial or near-complete absence of the iris, which can lead to symptoms such as light sensitivity, reduced vision and involuntary eye movements (nystagmus).

Because the gene involved in eye development affects several parts of the eye, people with congenital aniridia may also develop other eye conditions over time, including glaucoma, cataracts and corneal problems.

Syndromic aniridia

One example is WAGR syndrome, a rare condition associated with:

• Wilms tumour (a type of kidney cancer in childhood)
• Aniridia
• Genitourinary abnormalities
• Developmental differences

People with syndromic aniridia may require additional medical monitoring, as the condition can affect other organs and systems in the body.