Aniridia

What It Is, Causes, Signs and Symptoms, Diagnosis, and More

Author: Emily Miao, PharmD, MD

Editor: Alyssa Haag, MD

Editor: Lily Guo, MD

Editor: Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator: Abbey Richard, MSc

Modified: Mar 04, 2025

What is aniridia?

Aniridia is a rare abnormality characterized by the partial or complete absence of the iris, which is the colored portion of the eyes responsible for regulating the amount of light entering the eye. It’s often associated with various other ophthalmologic abnormalities such as cataracts and glaucoma. Aniridia may be seen in the presence of genetic disorders or on its own (i.e., isolated aniridia), and is estimated to occur in 1.8 of 100,000 births.

An infographic detailing the background, signs and symptoms, diagnosis, and treatment of aniridia.

What causes aniridia?

The exact mechanisms of aniridia are poorly understood, however, it is thought to be related to mutations in the PAX6 gene, a gene located on chromosome 11 that is crucial in the embryonic development of tissues, particularly the eyes, central nervous system, and pancreas. Other hypotheses include the mesodermal theory, which suggests that abnormal development in the mesodermal tissues such as the optic nerve, results in optic nerve hypoplasia, and subsequently aniridia.

While most cases of aniridia are congenital or present at birth, there are rare cases in which it may be acquired (e.g., trauma, complications from ocular surgery). Congenital familial aniridia may be transmitted in an autosomal dominant pattern, which requires only one genetic mutation from the affected parent to cause disease; or in an autosomal recessive pattern, which requires one genetic mutation from each affected parent to cause disease. When aniridia is transmitted in an autosomal recessive pattern, it is often seen in the presence of central nervous system abnormalities. When aniridia is present in conjunction with cerebellar ataxia (i.e., loss of muscle coordination in the hands and legs, resulting in clumsy movements) and intellectual disabilities, it is known as Gillespie syndrome. Rarely, there may be sporadic aniridia, which occurs due to a de novo mutation of the PAX6 gene. Sporadic aniridia cases are associated with the development of Wilms tumor (i.e., rare kidney cancer) and its associated syndrome, which consists of Wilms tumor, aniridia, genitourinary abnormalities, and intellectual disabilities (i.e., WAGR syndrome).

What are the signs and symptoms of aniridia?

The most common sign of aniridia includes partial (e.g., small amount of iris present only) or complete absence of the iris, which presents as a noticeable lack of color in the eye. Children with aniridia may experience early visual impairments such as reduced visual acuity, dry eyes, nystagmus (i.e., involuntary rhythmic eye movements), ptosis (i.e., drooping eyelid), photophobia (i.e., increased light sensitivity) and impaired pupillary reflex (i.e., the pupil does not constrict adequately when a small amount of light is shone into the eye). Individuals with aniridia are also at increased risk of developing other ophthalmologic complications such as glaucoma (i.e., increased intraocular pressure) and cataracts (i.e., opacity of the lens) which, without intervention, may eventually lead to loss of vision. When aniridia is present in conjunction with syndromes like WAGR syndrome and Gillespie syndrome, there may be other associated anomalies such as genitourinary abnormalities (e.g., undescended testicles), and cerebellar ataxia, respectively. In both syndromes, intellectual disability may be present.

How is aniridia diagnosed?

Diagnosis of aniridia begins with a thorough review of symptoms and medical history. A focused ophthalmologic exam can help identify the defining feature of aniridia, which is the partial or complete absence of the iris. Other tests may include visual acuity testing to determine the level of visual impairment, if present, and a pupil examination, which evaluates the pupillary reflex (i.e., constriction of the pupil in response to light). A slit-lamp examination is an exam that is used to evaluate the structural parts of the eye (e.g., cornea, lens, anterior chamber) and can provide further detailed information (e.g., presence of cataracts). A dilated fundus examination (i.e., an eye exam in which eye drops are placed to cause pupil dilation, allowing for a detailed assessment of the retina and optic nerve) can identify optic nerve hypoplasia or retinal abnormalities, if present.

Additionally, genetic testing helps confirm the genetic variant that is responsible for causing aniridia (e.g., PAX6) and this is accomplished using next-generation sequencing methods that analyze the individual’s DNA. If other features are present that are suspicious for aniridia-related syndromes, then additional imaging studies (e.g., ultrasound, computed tomography, magnetic resonance imaging) can be used to identify structural abnormalities.

How is aniridia treated?

There is currently no cure for aniridia, therefore treatment consists of supportive care measures aimed at improving visual acuity, increasing quality of life, and decreasing aniridia-related complications. It is recommended for affected individuals to establish care with an ophthalmologic specialist to receive regular eye exams, and prevent and manage any eye-related conditions, if present. Non-pharmacologic measures include the use of sunglasses or tinted glasses to reduce light sensitivity in environments with bright light exposure, and the use of artificial tears to lubricate dry eyes. Corrective lenses or prescription glasses can be prescribed to improve visual acuity and address refractive errors. Aniridia-related complications such as glaucoma can be treated with medications, like prostaglandin analogs (e.g., latanoprost, bimatoprost); and cataracts can be managed with surgical intervention. Vestibular rehabilitation may be helpful for individuals who suffer from nystagmus. Finally, if a genetic mutation is detected, genetic counseling may be offered to the affected individual and their family, to better understand the condition and how it can affect offspring.

For genetically-associated syndromes such as WAGR syndrome, treatment is aimed at surgical removal of the tumor, reducing kidney-associated complications (e.g., avoiding nephrotoxic medications, ensuring adequate hydration), and early educational and speech/language interventions to address intellectual disabilities and developmental delays.

What are the most important facts to know about aniridia?

Aniridia is a rare abnormality characterized by the partial or complete absence of the iris and is often associated with various other ophthalmologic abnormalities. The exact mechanisms of aniridia are poorly understood, however, it is thought to be related to mutations in the PAX6 gene, located on chromosome 11. While most cases of aniridia are congenital, there are rare cases in which it may be acquired. The most common sign of aniridia includes partial or complete absence of the iris, which presents as a noticeable lack of color in the eye. Aniridia is diagnosed with a variety of ophthalmologic exams and genetic testing, which identifies the pathogenic variant. There is currently no cure for aniridia, therefore treatment consists of supportive care measures aimed at improving visual acuity, increasing quality of life, and decreasing aniridia-related complications.

References

Blanco-Kelly F, Tarilonte M, Villamar M, et al. Genetics and epidemiology of aniridia: Updated guidelines for genetic study. Arch Soc Esp Oftalmol (Engl Ed). 2021;96 Suppl 1:4-14. doi:10.1016/j.oftale.2021.02.002

Calvão-Pires P, Santos-Silva R, Falcão-Reis F, Rocha-Sousa A. Congenital aniridia: Clinic, genetics, therapeutics, and prognosis. Int Sch Res Notices. 2014;2014:305350. Published 2014 Oct 29. doi:10.1155/2014/305350

Daruich A, Duncan M, Robert MP, et al. Congenital aniridia beyond black eyes: From phenotype and novel genetic mechanisms to innovative therapeutic approaches. Prog Retin Eye Res. 2023;95:101133. doi:10.1016/j.preteyeres.2022.101133

Elsas FJ, Maumenee IH, Kenyon KR, Yoder F. Familial aniridia with preserved ocular function. Am J Ophthalmol. 1977;83(5):718-724. doi:10.1016/0002-9394(77)90139-8

Gour A, Tibrewal S, Garg A, Vohra M, Ratna R, Sangwan VS. New horizons in aniridia management: Clinical insights and therapeutic advances. Taiwan J Ophthalmol. 2023;13(4):467-478. Published 2023 Dec 20. doi:10.4103/tjo.TJO-D-23-00140

Lee H, Khan R, O'Keefe M. Aniridia: current pathology and management. Acta Ophthalmol. 2008;86(7):708-715. doi:10.1111/j.1755-3768.2008.01427.x