An Overview of Aniridia
Aniridia is a rare genetic eye disorder characterized by the complete or partial absence of the iris. The Greek term for “without iris,” aniridia is a congenital condition that affects both eyes. Other names for the disorder include absent iris, congenital aniridia, and irideremia. The iris is the colored part of the eye that controls the amount of light that enters into the eye by controlling the size of the pupil. The most visible part of the eye, the iris also determines the color of your eyes. People with blue or light eyes have less pigmented irises than people with brown or darker colored eyes. The effects of aniridia can vary significantly between people. In some people with aniridia, the iris may be only mildly affected. In others, however, the effects can be profound. he iris may be affected by aniridia can vary significantly from person to person. Aniridia can reduce visual acuity and increase sensitivity to light.
Aniridia causes slight to extreme underdevelopment of the iris. In some people, the underdevelopment of the iris is hardly noticeable to the untrained eye. In some people, the iris may only be partially missing. Others may have complete absence of the iris. However, in people with complete absence of the iris, some iris tissue can usually be found during a thorough eye examination under a microscope. Besides affecting the iris, aniridia can also cause the following symptoms. The severity of symptoms is typically the same in both eyes. These symptoms and complications may be noted:
- Light sensitivity: Some people may experience an increased sensitivity and aversion to light, known as photophobia, as the iris helps block and absorb some of the light entering the eye. Glare, a visual phenomenon caused by excessive and uncontrolled brightness, can also become a problem.
- Corneal problems: People with aniridia lack limbal stem cells of the conjunctiva. Sometimes the cornea, the transparent dome-shaped tissue that forms the front part of your eye, can become scarred because of a deficiency of these cells. Limbal stem cells help to maintain the health and integrity of the cornea. Corneal scarring can cause impaired vision.
- Glaucoma: Aniridia may cause an increase in eye pressure, resulting in glaucoma. This usually appears in late childhood to early adolescence. Glaucoma is known as the “sneak thief of sight” because it often goes undetected and causes irreversible damage to the eye.
- Cataract: People with aniridia are at a greater risk for developing cataracts and other lens abnormalities. A cataract is clouding of the eye’s lens.
- Nystagmus: Sometimes infants with aniridia can show signs of nystagmus, an involuntary rhythmic shaking or wobbling of the eyes. Nystagmus can be horizontal or vertical or move in a diagonal direction. It is commonly referred to as “dancing eyes.”
- Retinal problems: Aniridia can cause underdevelopment of the fovea, part of the retina responsible for fine visual acuity.
- Wilms tumor: Around 30 percent of people with aniridia can have Wilms tumor,2 a rare kidney cancer that primarily affects children.
Aniridia is a genetic disorder, meaning it is inherited. The disorder is caused by mutations in the PAX6 gene, which plays a critical role in the formation of tissues and organs during embryonic development. These mutations disrupt the formation of the eyes. Aniridia occurs in 1 in 50,000 to 100,000 newborns worldwide.
Aniridia is usually detected at birth. The most noticeable feature is that a baby’s eyes are very dark with no real iris color. The optic nerve, retina, lens, and iris can all be affected and may cause visual acuity problems depending on the extent of underdevelopment.
Diagnosing a genetic or rare disease can be challenging. Health care professionals will inquire about a person’s medical history and symptoms. A thorough physical exam will be performed, as well as a complete eye examination. An eye doctor will be able to note abnormalities of the iris, and possibly other structures of the eye. Genetic and laboratory testing will be required in order to make a formal diagnosis.
Aniridia affects the eyes in many ways, and affects people at different severity levels. Treatment for the disorder can take many forms.
- A comprehensive eye exam along with a doctor who specializes in low vision will be very beneficial, as some people with aniridia have poor visual acuity. Low vision devices, along with rehabilitation services and training, can be extremely helpful for some individuals with aniridia.
- The underdevelopment of the iris is sometimes obvious. In order to improve the appearance of the eye, opaque or colored contact lenses are often worn. Lenses can also improve vision and minimize light sensitivity and glare. Sunglasses can also be worn to help with the symptoms of photophobia.
- Some people with aniridia are candidates for surgery to replace a small or missing iris with an artificial iris. Many eye surgeons may not recommend the procedure because it may cause unnecessary complications.
- The health of the cornea may be improved by keeping it lubricated with the use of artificial tears. Your doctor may recommend a specific artificial tear for maximum lubrication.
- Some corneal problems may require surgery, including corneal transplants. Also, stem cell transplantation to replace missing stem cells can improve the function of the cornea.
- Cataract surgery may be required in people who develop clouding of the lens of the eye.
- If glaucoma develops, treatment will include medications to lower eye pressure, lasers, or surgery to preserve vision.
The diagnosis of aniridia may come as a complete shock. Support and advocacy groups can help people connect with other patients and families, and they can provide helpful services. If your baby is born with aniridia, the child will have some vision. Treatment will be highly encouraged to preserve and maintain this vision. Support is available to help families adapt to difficulties they may face with developmental delays or low vision needs.
Early intervention is very important if your baby is diagnosed with aniridia. Treatment will focus on preserving vision and improving your baby’s vision through visual aids and/or surgery. Therapists will work with your baby to help the child develop as normally as possible.
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