Rare eye diseases
Aniridia is defined as the partial or complete absence of the iris (the coloured ring inside the eye around the pupil). It may be caused by a trauma, complicated surgery or a genetic disorder.
Congenital aniridia is an autosomal dominant inherited disease. It is chronic and generally affects both eyes. It is due to a mutation that hinders proper development of the eyeball during the first few weeks of gestation. It affects approximately 1 out of every 80,000 people. Throughout life it may cause different degrees of visual incapacitation.
The most common symptoms of aniridia are poor vision, glare, photophobia and the external appearance of an eye with a large and irregular-shaped pupil.
Although the word aniridia alludes to the absence of an iris, it's actually an eye disease that affects different parts of the eye. This may cause uncontrollable movements of the eye that impede fixation (nystagmus), cataracts, glaucoma, corneal degeneration, crystalline lens luxation, strabismus and and atrophy of the optical nerve.
In exceptional cases, aniridia can be associated with systemic pathologies such as Wilms tumours, intellectual disability and genitourinary anomalies.
Aniridia is detected in the first few days of life. The absence of an iris means that the newborn feels more comfortable in the shade with their eyes closed when there are light stimuli. If this reaction is found, the child has to be taken to the ophthalmologist who will determine the severity of the condition, possible associated conditions and they will schedule the pertinent check-ups.
Congenital aniridia is caused by a genetic mutation, which is the result of an alteration to the PAX-6 gene, responsible for the formation of the eye during pregnancy.
Aniridia can be sporadic or hereditary. In sporadic cases, there is no family history of the disesase. At that point, it becomes an autosomal dominant hereditary condition with a 50% chance of passing the alteration to direct descendents.
Aniridia cannot be prevented. For that reason, it is important that children born with this illness undergo a genetic diagnosis. Exhaustive annual monitoring has been undertaken by specialisd paediatricians and ophthalmologists in order to detect and determine the degree of the lesion and treat the associated pathologies early on to give patients the best quality of life for as long as possible.
Currently, there is no treatment for aniridia, but it is possible to treat associated conditions (cataract, glaucoma, corneal conditions, etc).
During childhood, there is the chance of early visual stimulation to develop the eyesight and psychomotor functions. Depending on each case, a series of visual aids such as magnifying glasses, mini telescopes or computer programmes, etc. can be used.
The use of cosmetic contact lenses is an option for photophobia and aesthetic issues, but current eye microsurgery can, in many cases, be undertaken to reconstruct the iris and the pupil, if there are partial defects. For total or subtotal defects, 90° or 180° ring implants that form a complete iris can be used. The newest type is the Artificial Iris (Dr. Schmidt, HumanOptics), a flexible iris of a personalised colour (based on photographs), which can be implanted without the need for any sutures.