Why does aniridia or absence of an iris occur?

Aniridia is a rare pathology characterized by total or partial absence of the iris. . The iris is the diaphragm that surrounds the pupil and gives the eye its color. Its primary function is to regulate the amount of light entering the eye. Find out the causes of aniridia or absence of iris in this article.

Aniridia is a condition that affects 1 in 100,000 people and can result in the complete or partial absence of the iris.

An eye without an iris receives light indiscriminately like a window without curtains.


Aniridia is an eye disorder characterized by incomplete development of the iris, affecting both eyes. The absence of the iris can be total or partial, but both cause severe visual impairment.

If the iris is missing, other parts of the eye are also affected.  Commonly accompanied by corneal degeneration, lens dislocation, cataract, glaucoma, nystagmus, strabismus or optic nerve atrophy .

It is a congenital disorder, usually due to a genetic mutation. Although considered a chronic pathology, there are treatments available to alleviate its effects.

aniridia symptoms

Aniridia can be detected from the first day of life. Newborns prefer to be in the dark and close their eyes to light stimuli. This disease results in a marked decrease in visual acuity and other ocular pathologies.

Common symptoms of aniridia include:

  • low vision
  • glare
  • photophobia

The most distinctive feature is usually an irregularly shaped pupil larger than normal. There is also a decrease in visual acuity with associated defects such as nearsightedness, hyperopia, or astigmatism.

In addition, the sensitivity of the retina is low, so there may be amblyopia or deterioration of vision. Glaucoma is also present in up to half of patients with aniridia. And it is not uncommon for pathology to cause cataracts.

baby's iris.

Aniridia is present from birth. Babies have serious difficulties with tolerating ambient light.


The direct cause is usually a mutation in the PAX-6 gene on chromosome 11 . It is responsible for eyeball formation in early pregnancy.

The most obvious sign is a complete or partial absence of an iris, but mutations in this gene often cause problems in other parts of the eye as well. About one-third of patients have sporadic iris, and the mutation occurs spontaneously and is not inherited.

This disease has an autosomal dominant pattern of inheritance . People with aniridia have a 50% chance of passing this pathology on to their immediate descendants.

There is no way to prevent pathology.

In rare cases, aniridia is associated with other systemic diseases such as Wilms’ tumor and may be the result of eye trauma.

Aniridia Diagnosis

The diagnosis of iris is simple. In order to detect partial or total absence of the iris, it is sufficient to observe the size and shape of the pupil, which can be confirmed with the naked eye without a separate examination.

However, it is important to determine the severity of the anomaly by performing some tests. In some cases, it can be confused with another condition called iris coloboma.

For this reason, the following tests are usually requested.

  • Fluorescent in situ hybridization (FISH)
  • chromosome banding
  • Abdominal and Brain Imaging
  • kidney ultrasound

aniridia treatment

So far , there is no specific treatment for aniridia . The general approach uses separate approaches for associated glaucoma and associated anomalies such as cataracts.

There is potential for early visual stimulation in childhood, so develop the maximum possible visual potential and avoid motor problems.

Many patients overcome photophobia and correct eye abnormalities by wearing cosmetic contact lenses.

If the defect is partial, it can be corrected with microsurgery . It allows reconstruction of the iris and pupil, and in some cases the eye can be transplanted to form a complete iris if the defect is very severe.

Iris or iris absence.
Although incomplete iris reconstruction is possible, it is not an easy task and the results are not always good.


The prognosis for treatment of aniridia is highly variable and depends on the severity and characteristics.

For the same reason, treatment must be individualized. Your doctor will not only improve or cure the condition, but also prevent possible complications.

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