Homepage

About Us

About Aniridia

Living with Aniridia

The Aniridia Directory

Join Us

Contact Us

Make A Donation

Web www.aniridia.org

Anatomy

The front of the eye is made up of two types of surface, or epithelial, cells.

The Conjunctival:
This is a transparent layer that lines the white of the eye (the sclera) and the inside of the eyelids.

The Cornea Epithelia:
These are clear cells that cover the surface of the cornea, the transparent part of the front of the eye which allows light to enter.

Both types of cell are created from stem cells and appear be continuous. However, each type of cell is distinctive. They are separated by an area called the corneaschlearal limbus. This is where the stems cells called the limbal palisade of vogt reside, these cells become cornea epithelia cells.

What can go wrong?

The corneaschlearal limbus acts as a barrier between the conjunctival and the cornea epithelia. however, when the limbus does not produce enough stem cells the conjunctival is able to invade the cornea epithelia. This is called "conjunctivisation" this accompanied by "vascularisation" the development of blood vessels in the cornea, and the appearance of goblet cells, column-shaped cells that secrete mucus. These symptoms give the cornea an irregular and unstable surface. For the patient this can cause discomfort and reduced vision.

Why Does This Develop In Aniridia?

In aniridic eyes the production of stem cells at the limbus is weak. often In aniridia, production may be reduced at birth or during childhood and the conjunctiva starts to invade the cornea epithelia. However, this is limited to the periphery of the cornea and therefore does not affect vision. Productivity at this level may remain stable well into adulthood.

However, often in aniridia production of stem cells can fall very low and the conjunctiva invades the whole of the cornea epithelia. This can make the persons vision very poor.

Treatment

Partial Keratopathy which does not affect the vision may go untreated in a person with aniridia.

However a number of important issues have to be considered

1) Contact lenses must be appropriate. The type and frequency of use must be tailored to avoid any unnecessary scaring

2) Eye surgery for glaucoma and cataracts may cause the development of aniridic keratopathy, therefore doctors must consider the best use of surgery to minimise this risk, it is important to consider the high risk for multiple surgeries in aniridia.

Total Keratopathy, that does affect a persons vision, may be treated in three ways.

1) Limbal Autograft: This is when stems cells from the persons healthy eye are placed into the affected eye. This is only affective when the condition is unilateral. However this is unlikely in most cases of aniridic keratopathy because it follows aniridia's bilatera pattern and it usually occurs in both eyes at the same time though the extent may vary.

2) Limbal Allograft: Stems cells from a live or deceased donor are collected and transplanted into the affected eye(s). This treatment can be affective for Bilateral Aniridic Keratopathy, however it requires the patient to use immunosuppressive drugs, and risk of rejection is moderately high.

3) Amniotic Membrane Transplant. Stem cells are grown on an amniotic membrane and then this is transplanted on the affected eye. This procedure is affective for bilateral conditions and does not require the patient to use immunosuppressive drugs.