Aniridia refers to a rare eye condition in children where the iris is partially or completely absent. The iris is the round, colored dot that forms the pupil at the center of the eye. It controls how much light enters the eye. Problems with the iris can present serious visual issues. The term aniridia means 'no iris’, and it can be present at birth or develop later. The congenital type affects both eyes, although the two eyes may not be affected the same.
Aniridia is often associated with abnormalities involving the cornea, such as abrasions (scratches on the cornea) leading to scarring, glare, and blurry vision. It can also be associated with glaucoma when the angle structures near the iris are affected. The eye's natural lens may also be affected, leading to a cataract (clouding of the lens). Hypoplasia is related to aniridia too, where the optic nerve is affected, while an affected retina can cause foveal hypoplasia (underdevelopment of the part responsible for providing sharp central vision). Visual quality may be affected if nystagmus or shaking of the eyes is present. Large and oddly shaped pupils may be associated with aniridia, leading to photophobia or light sensitivity. The presence of these conditions means that vision may deteriorate progressively.
Some children with aniridia may still have very good vision and not suffer many eye problems.
Also Known As
- Absent iris
- Congenital aniridia
- Acquired aniridia
- Congenital aniridia which is divided into:
- Sporadic congenital aniridia
- Autosomal recessive congenital aniridia
- Autosomal dominant congenital aniridia
- Sporadic congenital aniridia
Causes & Risk Factors
Congenital aniridia is caused by mutations in the PAX6 gene, although nearby genes may be affected. It is thought to occur during pregnancy, between the 12th and 14th weeks. The disorder may occur as part of a syndrome. For instance, it is related to Wilms tumor, a kidney tumor, and Gillespie syndrome. The development of Wilms tumor is linked to sporadic aniridia cases. Other diseases associated with aniridia are systemic and include obesity, autism, diabetes, neurological problems, and metabolic conditions. Acquired aniridia is caused by trauma or eye surgery.
Signs & Symptoms
The signs and symptoms of aniridia may include:
- Poor vision
- Kidney tumor, intellectual disability, mental retardation, or genitourinary issues in some patients
Aniridia can be diagnosed in the following ways:
- The child’s medical and family history
- Genetic testing is performed to confirm the diagnosis
- A complete eye examination of the child and family members too
- Imaging tests such as fundus fluorescein angiogram and optical coherence tomography
- A physical examination of the affected child. The examiner may see a small rim of the iris
- A test called ultrasonogram should be performed regularly to eliminate the possibility of Wilms tumor
The goal of treating aniridia is to improve vision and possibly physical appearance. Improving vision involves treating the many conditions associated with aniridia.
Treatment options include:
- Treatment of amblyopia and correcting squint
- Correcting refractive errors using glasses prescribed by an ophthalmologist
- The concerned specialist treating systemic conditions. For instance, diabetes is managed through medications
- Corneal problems which can be managed by artificial tears and ointments. These help to lubricate the eye. A limbal stem cell transplant can treat corneal scarring
- Treatment for photophobia using painted or tinted contact lenses which also improves physical appearance. Tinted lenses can help decrease nystagmus too. Tinted or photochromatic glasses may also assist
- Cataracts are treated through cataract surgery. A tinted intraocular lens (IOLs) and special aniridia IOLs replace the extracted natural lens. The tinted IOL can help reduce photophobia
- Surgery with artificial iris implantation to treat both congenital and acquired aniridia. However, it may cause or worsen glaucoma. Low vision devices such as magnifying glasses and telescopes can help manage low vision
- Glaucoma treatment using medications and surgery. Often, the medicine fails to work, necessitating surgical intervention such as goniotomy and trabeculectomy. Managing glaucoma in children under one year may be challenging. However, glaucoma that does not respond to medication or surgery can be addressed by laser procedures such as cyclocryotherapy and diode laser cyclophotocoagulation
Prognosis & Long-Term Outlook
Most children with aniridia have poor vision, described as visual acuity of 20/100 or worse in the eye that sees better. The poor vision is due to the complications that arise, such as glaucoma, aniridia-related keratopathy, cataracts, optic nerve problems, and retinal detachment.
Most children with aniridia go to regular schools, thus, caregivers and teachers in these schools should be aware of a child's condition. The teachers and caregivers are taught how to spot complications like cataracts.
Prevention & Follow Up
Because of the risk of developing severe complications, regular screening or follow-up is necessary. The follow-up should include various categories of eye specialists. Moreover, follow-up is for life, but the schedule is informed by which other conditions are present. For children with severe disease and those who are very young, frequent examination is a must. Regular screening using ultrasonography is recommended for all sporadic congenital aniridia for Wilms tumor. The screening duration depends on age. Children under five years are screened every three months while those between 5-10 undergo screening every six months. Children/adolescents aged 10-16 years have an annual screening session.