Congenital aniridia

This is part of Rare diseases.

Diagnosis: Congenital aniridia

Synonyms: Aniridia


Date of publication: 2014-10-09
Version: 2.0

ICD 10 code


The disease

Congenital aniridia is a serious eye disorder that often causes pronounced visual impairment. The word aniridia refers to the complete or partial absence of the iris, which leads to light sensitivity. The primary cause of impaired vision is underdevelopment of the macula, the small yellow-pigmented area on the retina responsible for central, high-resolution vision.

The disorder has been known since the early 19th century.

Aniridia may also be a sign of WAGR syndrome and Gillespie syndrome. Both these disorders are separately described in the rare disease database of the Swedish National Board of Health and Welfare.


In Sweden, congenital aniridia is diagnosed in approximately two or three people out of every 100,000. The total number of people with aniridia in Sweden is approximately 200. The disorder is equally distributed between the sexes.

Since the late 1970s, eye examinations have been part of the Swedish neonatal screening programme and as a result the disorder is now discovered early in life.


Congenital aniridia is caused by a mutation in the PAX6 gene, located on the short arm of chromosome 11 (11p13). The PAX6 gene is responsible for eye development, but also plays a role in the development of the brain and pancreas. This gene is a homeobox gene, meaning that it regulates several other genes. Individuals with congenital aniridia have only one functioning copy of PAX6, rather than the normal two.

A mutation in PAX6 affects many parts of the eye. Certain defects can be identified at birth. The iris, the lens, the surface of the cornea and the outflow from the eye (the chamber angle) are all affected. In addition, the retina (including the macula) and the optic nerve fail to develop normally, which leads to varying degrees of visual impairment. These anomalies are irreversible, but their severity varies.


The inheritance pattern of congenital aniridia is autosomal dominant. This means that one of the parents has the disease, and so has one normal gene and one mutated gene. Sons and daughters of this parent have a 50 per cent risk of inheriting the disease. Children who do not inherit the mutated gene do not have the disease and do not pass it down.

Figure: Autosomal dominant inheritance 


Congenital aniridia is a condition in which the iris is wholly or partially absent. Most people with aniridia do not have a visible iris. Even in newborns it will be evident that the pupils are abnormally large, and that only traces of peripheral iris tissue remain. The absence of the iris causes extreme light sensitivity.

Figure: Cross-section of eye

Figure: Cross-section of eye

Visual impairment is usually evident very early in life in children with aniridia. The cause is congenital underdevelopment of the retina, in particular the macula, which is the part of the eye responsible for high resolution vision. Visual acuity varies, but most people with aniridia have pronounced vision loss and require visual aids. In some cases, however, visual acuity remains good.

Complications are common, and may lead to further deterioration in vision. Examples of eye conditions associated with congenital aniridia are described below.

One abnormality is keratopathy, mainly on the surface of the cornea (corneal epithelium). This is found in most people with the condition including infants.

The corneal epithelium is renewed throughout life with the help of specialized stem cells located in the intermediary zone between the cornea and the conjunctiva, in what is known as the limbus area. Normal development of these stem cells requires the presence of a specific microenvironment, which allows the immature stem cell to develop into a corneal epithelial cell. PAX6 regulates other genes that in turn affect this microenvironment, known as the stem cell niche. This means that when a PAX6 mutation prevents these other genes from functioning correctly, the stem cells form defective epithelial cells. As a consequence, the natural barrier between the cornea and conjunctiva is impaired, allowing blood vessels from the conjunctiva to migrate into the surface of the cornea. Changes begin in the outer, peripheral part of the cornea, in the form of cloudy areas and blood vessels. In aniridia, these cloudy areas have a characteristic appearance. In later stages of the disease they expand, nearing the central part of the cornea, and cause progressive loss of vision. The corneal changes cause painful lesions as a result of the impaired ability of the eye to heal itself.

In individuals with aniridia, cataracts begin earlier than usual and may even occur in infants. However, it is unusual to be born with cataracts. More than half of all people with aniridia will develop cataracts. Cataract operations in people with aniridia are more risky than normal, partly because of abnormalities in the structure which holds the lens of the eye in position. The lens may also become displaced (luxated).

Glaucoma associated with aniridia is usually caused by chamber angle defects. The nutritional fluid (the aqueous humour) of the eye is produced in the posterior chamber angle and transported into the pupil, after which it is drained from the eye via the anterior chamber angle through specific ducts (the trabecular meshwork and Schlemm’s canal). Structural anomalies may prevent adequate drainage, which causes an increase in eye pressure. The increase in pressure may damage the optic nerve, thereby decreasing vision further. Glaucoma develops in over 50 per cent of all people with congenital aniridia and often requires advanced medical treatment. Some people are born with glaucoma (congenital glaucoma), but more commonly the condition develops in adolescence or later – up to early middle age (secondary glaucoma). In congenital glaucoma the drainage channels in the anterior angle chamber are often obstructed by a membrane containing blood vessels that originate in the iris. In secondary glaucoma the blockage of the drainage channels is more likely to be caused by debris from the iris. In both types of glaucoma, Schlemm’s canal may be absent. Without proper treatment, glaucoma may cause irreversible vision loss or blindness.

In aniridia, tear production is normal, but the tear fluid lacks normal viscosity. This means that people with aniridia are more prone to develop irritation on the surface of the eye, as the normal protective function of the tear fluid is impaired.

Nystagmus (involuntary rapid, jerky eye movements) is common in people with congenital vision loss. Approximately three quarters of all people with aniridia have some type of nystagmus. This is caused by the underdevelopment of the macula and the retina, which means individuals with the condition may not be able to fix their gaze on a single point.


Aniridia is usually diagnosed in newborns, as major parts of the iris are missing and the infants are very sensitive to light. The pupils are abnormally large, with only a small amount of iris tissue visible. The degree of iris underdevelopment varies, and sometimes only minor parts of the iris are missing. The eyes of a single individual may be differently affected.

If the disorder is suspected, the child should always be examined by an ophthalmologist. Small children may have to be examined under anaesthesia. In practically all cases the central part of the macula is underdeveloped (macular hypoplasia). Even in small children it is possible to detect specific abnormalities in the peripheral cornea. These abnormalities are often crucial in making a correct diagnosis. Chamber angle defects are also common. Pressure in the eye should always be measured.

If the disorder is present in other family members, any suspicion of the condition will be strengthened as most children with aniridia have a parent with the same condition.

DNA analysis can be used to detect PAX6 mutations, in which case the diagnosis is confirmed. Children with confirmed aniridia, who do not have the condition in their family, should undergo genetic testing, primarily to exclude a mutation in the nearby gene WT1. A deletion which includes both PAX6 and WT1 can cause WAGR syndrome (W stands for Wilms tumour, a malignant kidney tumour, primarily affecting small children, A stands for aniridia, G stands for uroGenital abnormalities, and R stands for mental Retardation).

At the time of diagnosis it is important that the family is offered genetic counselling. Carrier and prenatal diagnosis, as well as pre-implantation genetic diagnosis (PGD) in association with IVF (in vitro fertilization), are available to families where the mutation is known.


People with aniridia should be monitored regularly by an ophthalmologist throughout life. One reason why this is important is to detect glaucoma as early as possible. Even if they appear asymptomatic, children of individuals with aniridia should be examined by an ophthalmologist once or twice, although they do not need to be monitored throughout life. Eye drops that lower intraocular pressure are the first-line treatment in glaucoma management, but surgical intervention is more common at a later stage. Children who are born with glaucoma usually undergo surgical intervention early in life.

The eyes of people with aniridia are very sensitive to intraocular surgery, which may affect for example cataract operations. A serious complication is damage to the cornea, resulting in lesions and increased clouding. Before the physician has discussed the option of an operation with the patient and reached a decision, potential gains should be weighed against risks.

Owing to abnormal tear composition, all people with aniridia should be treated with tear replacements (applied as eye drops or ointment). Tear replacement therapy may reduce pain and abnormal light sensitivity caused by cracks in the corneal surface.

Eye drops should be free of preservatives as these may cause damage to the corneal epithelial.

Where the cornea is cloudy, conventional corneal transplantation is not helpful, but may rather worsen the condition. However, by transplanting stem cells into the cornea it is possible to achieve prolonged improvement. Just as in other types of transplantation, the surgical procedure is followed by long-term immunosuppressive therapy in order to prevent organ rejection. This treatment is associated with many side-effects.

Individuals with impaired vision require habilitation in order to learn to make full use of their vision, or to learn techniques to help compensate for visual disabilities. Spectacles should be prescribed where necessary, while contact lenses are usually not recommended as the cornea is very sensitive. Magnifying visual aids may be provided, such as magnifiers, special eye wear for close-up work, enhanced-vision TV systems and computers, and the children should be trained in using them. Spectacles with filters may improve contrast vision and decrease light sensitivity. It may be necessary to adapt lighting.

In many cases the environment needs to be adapted to compensate for impaired vision. This applies to the physical environment, but the social environment is similarly important and people need to know how to meet these children and young people in a positive way.

Children with visual impairments go to mainstream pre-schools and schools but require specialist instruction and suitable educational materials. School staff will benefit from the knowledge and guidance a specialist teacher for the visually impaired can provide. The National Agency for Special Needs Education and Schools provides such resources. See below under “National and regional resources in Sweden”.

Having a visual impairment may affect both a person’s social life and choice of occupation. Much can be done to support the individual and compensate as much as possible for impaired vision. Pedagogical, technical, psychological and social support are adapted to age and life style.

Practical advice

The Aniridia Network in Sweden offers practical advice for parents and information on how to protect sensitive eyes from bright light, www.aniridi.se.

National and regional resources in Sweden

Resources for diagnosing eye conditions are available at eye clinics nationwide, and these units also offer genetic diagnostics.

Genetic diagnostics is carried out at Swedish university hospital departments of clinical genetics.

Resource Centre Vision is a national resource centre at the National Agency for Special Needs Education and Schools, www.spsm.se. The two units of the centre are located in Stockholm and Örebro. The centre offers special education assessments for children and young people with impaired vision, or with impaired vision in combination with other disabilities. Assessments are carried out locally as well as at the centres in Stockholm and Örebro, and always in collaboration with local resources.

Resource Centre for the Visually Impaired - Stockholm, Rålambsvägen 32 B, Box 121, SE-102 26 Stockholm, Sweden. Tel: +46 10 737 50 00. Email: rc.syn.stockholm@spsm.se.

Resource Centre for the Visually Impaired - Örebro, Eriksbergsgatan 3, SE-702 30 Örebro. Box 9024, SE-700 09 Örebro, Sweden.Tel: +46 10 473 21 00, fax: +46 19 676 22 00, email: rc.syn.orebro@spsm.se.

Resource personnel

Ulla Edén MD, PhD, Department of Opthalmology, The Faculty of Health Sciences, SE-581 85 Linköping, Sweden. Email: ulla.eden@gmail.com.

Professor Per Fagerholm, The Eye Clinic, Linköping University Hospital, SE-581 85 Linköping, Sweden. Email: per.fagerholm@liu.se.

Associate Professor Anna Lundvall, Paediatric Eye Clinic , St. Erik Eye Hospital, SE-112 82 Stockholm, Sweden. Tel: +46 8 672 30 00, email: anna.lundvall@sankterik.se.

Senior Physician Per Montan, St. Erik Eye Hospital, SE-112 82 Stockholm, Sweden. Tel: +46 8 672 30 00, email: per.montan@sankterik.se.

Professor Kristina Tornqvist, Department of Opthalmology, Lund University, Sweden. Email: kristina.tornqvist@med.lu.se.

Courses, exchanges of experience, recreation

Aniridia Sweden arranges events where knowledge of the condition can be shared. (See under “Organizations for the disabled/patient associations etc.”)

Resource Centre for the Visually Impaired in Stockholm is a national resource within the National Agency for Special Needs Education and Schools, which arranges parent training and other activities. Children with severe visual impairment and their parents attend courses before and during their pre-school years. Once at school, they are invited to attend group visits for a few days each year. Individual assessments aiming at evaluating functional vision, general development and the consequences of impaired vision are carried out by a multidisciplinary team. Schoolchildren may also come for training on an individual basis. For contact information, see under “National and regional resources in Sweden”.

The Swedish National Association for the Active Visually Disabled is a charity that organizes camps and other leisure activities: Box 42122, SE-126 15 Stockholm, Sweden. Tel: +46 8 744 15 93, email: kansli@aktivasynskadade.org, www.aktivasynskadade.org.

Organizations for the disabled/patient associations etc.

Aniridia Sweden, www.aniridi.se, email: info@aniridi.se. The network is chaired by Neven Milivojevic, Bygatan 19, 6 th floor, SE-171 49 Solna, Sweden. Tel: +46 70 6390068.
The Aniridia Network in Sweden is a national association for people with aniridia and their families.

There is also a European Aniridia network, Aniridia Europe, www.aniridia.eu.

Rare Diseases Sweden, Box 1386, SE-172 27 Sundbyberg, Sweden. Tel: +46 8 764 49 99, email: info@sallsyntadiagnoser.se, www.sallsyntadiagnoser.se. Rare Diseases Sweden is a national association representing people with rare diseases and varying disabilities.

SRF, The Swedish Association of the Visually Impaired, Sandsborgsvägen 52, SE-122 88 Enskede, Sweden. Tel: +46 8 39 90 00, email: info@srf.nu, www.srf.nu.

SGF, The Swedish Glaucoma Association, mobile tel: +46 702 91 56 66 (telephone hours 9 to 10 AM). Email: info@glaukomforbundet.se, www.glaukomforbundet.org.se.

Local associations are found in several areas of Sweden. For further information, contact SGF.

Courses, exchanges of experience for personnel

The Resource Centre for the Visually Impaired in Stockholm arranges courses for staff responsible for children with visual disabilities in pre-schools and schools. For more information, visit the website of The National Agency for Special Needs Education and Schools, www.spsm.se.

Research and development

Research on corneal changes associated with aniridia is currently ongoing at the Department of Ophthalmology (IKE), Faculty of Health Sciences, Linköping University.

Information material

Short summaries of all the database texts are available as leaflets, in Swedish only. These leaflets may be ordered or printed out. (See under “Mer hos oss” in the right hand column.)

The Norwegian Patient Association, Aniridia Norway, has produced a handbook on the subject of living with aniridia: “Om å leve med aniridi” (2011; in Norwegian only). It is available in PDF format on their website: www.aniridi.no/handbok/

Aniridi (2010). Information is available at the Norwegian Centre for Rare Disorders, Oslo University Hospital HF, Rikshospitalet, 4950 Nydalen, NO-0424 Oslo, Norway. Tel: +47 947 23 07 53 40, email: sjeldnediagnoser@oslo-universitetssykehus.no. The leaflet is available as a PDF at: www.sjeldnediagnoser.no/docs/PDF/Diagnosefoldere/Aniridi_11_ny%20mal.pdf.

The Centre for Rare Disorders also produces a document with questions and answers from the European Conference on Aniridia (Oslo 2012): www.sjeldnediagnoser.no/docs/PDF/Annet/Spoersmaal%20om%20aniridi.pdf.

There is a book in English on aniridia and WAGR syndrome: A guide for patients and their families (2010), by Jill Ann Nerby, Jessica J Otis. ISBN 0195389301.


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Database references

OMIM (Online Mendelian Inheritance in Man)
Search: aniridia

GeneReviews (University of Washington)
www.genetests.org (select GeneReviews, then Titles)
Search: aniridia

Document information

The Swedish Information Centre for Rare Diseases produced and edited this information material.

The medical expert who wrote the draft of this information material is Ulla Edén MD, Department of Ophthalmology, Faculty of Health Sciences, Linköping University.

The relevant organizations for the disabled/patient associations have been given the opportunity to comment on the content of the text.

An expert group on rare diseases, affiliated with the University of Gothenburg, approved the material prior to publication.

Date of publication: 2014-10-09
Version: 2.0
Publication date of the Swedish version: 2014-03-25

For enquiries contact The Swedish Information Centre for Rare Diseases, The Sahlgrenska Academy at the University of Gothenburg, Box 422, SE-405 30 Gothenburg, Sweden. Tel: +46 31 786 55 90, email: ovanligadiagnoser@gu.se.  


About the database

This knowledge database provides information on rare diseases and conditions. The information is not intended to be a substitute for professional medical care, nor is it intended to be used as a basis for diagnosis or treatment.