Many eye diseases affect only one eye, described medically as being unilateral.
Some eye diseases on the other hand affect both eyes at the same time, in this case being described as bilateral.
Aniridia is a particular eye disease that affects eyes bilaterally and it’s a good job that it does, since if only one eye were to be affected, the person suffering from the disease would probably look quite odd!
Aniridia is a disorder affecting the iris – the Greek prefix “an” being used to indicate the iris in each eye is absent, or not well formed. Since it is the iris that normally surrounds the dark pupil and gives the eye its colour, with aniridia there is no colour, merely a larger looking black pupil!
Unfortunately the lack of an iris means problems are created in other parts of the eye – the cornea, the lens within the eye and the light sensitive retina at the back. The lack of an iris can lead to a variety of related disorders:
• Dry eyes and corneal degeneration – affects vision
• Nystagmus – rapid involuntary movements of the eyes
• Strabismus – when the eyes do not line up in one direction properly (sometimes called lazy eye)
• Glaucoma – eye pressure damages the optic nerve leading to vision loss
Those with aniridia will usually present with one or more of the above related disorders – fortunately not all of them.
Congenital, that is to say present at birth, aniridia is quite rare, affecting on average some one person in 80,000 worldwide, and in those cases around thirty per cent have a family history of the disorder.
A paediatric ophthalmologist is usually the first to notice something untoward. Presence of the condition is usually indicated when the pupil fails to change in diameter with changes of light in the eye.
The list of related disorders also acts as a list of symptoms that are sometimes observed, with sensitivity to light – photophobia – being additional.
Slit lamp tests are preferred due to difficulties experienced with any photophobia and any involuntary eye movements from a nystagmus. Flash pictures can be taken not only to show the opacity of the cornea and condition of blood vessels but can provide a reference base for a future photographic record.
Blood tests if expense permits can determine any genetic correlation.
Aniridia and its associated symptoms remain with someone who suffers from it throughout their life, however the co-disorders are treatable meaning the aniridia itself is not degenerative – it doesn’t get any worse.
Dry eyes can be treated with over the counter drops to prevent ulcers forming on the cornea.
The degree to which normal vision is impaired varies from being permitted to drive a car to be declared legally blind.
It is essential that parental education is given regarding the possible developments of the co-disorders, particularly glaucoma, as this may require careful monitoring. Also parents should be offered counseling in relation to any genetic factors involved.
Typically glare discomfort needs managing. At The Eye Practice we specialise in complex contact lens fittings. Sometimes it is possible to fit contact lenses that cosmetically create an artificial iris, which reduces glare discomfort dramatically. The image above shows a patient with aniridia and below has been fitted with cosmetic contact lenses.