Glaucoma in aniridia

Glaucoma is damage to the optic nerve caused by an increase in eye pressure. This damage causes sight loss over time if the eye pressure is not successfully controled.

In the front section of the eye between the lens and the cornea is filled with a liquid known as the aqueous humour, this is continually being made by a section of the cillary body (which makes up the iris and the muscles around the lens) and old aqueous humour drains away through an area called the trabecular meshwork which is between the cornea and the iris.

In babies and young children with aniridia the trabecular meshwork may be underdeveloped.  If this is the case the aqueous humour cannot drain away in sufficiently and the eye pressure increases. This type of glaucoma is called congential glaucoma and is not the most common form of glaucoma in aniridia.

In older children and adults with aniridia, the tiny part of the iris that is present in the aniridic eye (but not visable to other people) covers the trabecular meshwork preventing the aqueous humour from draining away and again eye pressure increases. This type of glaucoma is more common and is believe to occur in anything from 6% to 75% of people with aniridia. This type of glaucoma called secondary or aniridic glaucoma and is believed to be most commonly diagnosed in the first 3 decades of life, however, the risk of glaucoma remains high throughout life.

Eye pressure may also increase and glaucoma may occur in people with aniridia after eye surgery. 

It is very important for signs of glaucoma to be identified and treated as soon as posible, as a delay in diagnosis can cause perminent vision loss and the glaucoma may become difficult to treat medically and surgically. Therefore it is suggested that people with aniridia are checked once a year for signs of glaucoma.

The first test in detecting glaucoma is to check eye pressure. this there are avariety of ways to check eye pressure.

the second test is a gonioscopy. This is a  measure of  the angle between the iris stump and the cornea by using a special mirror that is put against the cornea while the eye is under topical anesthesia.

The third test is to look at the back of the eye and see if there is any damage to the optic nerve.

Patients may be unaware that their eye pressure has increase as the only experiences pain when they pressure is extremely high.

Treatment of glaucoma.

Glaucoma is a condition that cannot be cured, so if a person with aniridia is found to have increaseed eye pressure or glaucoma, treatment seeks to stablise eye pressure and in doing so prevent glaucoma or the progression of glaucoma.

There are several options to stablise eye pressure.

At first, medication, eye drops and/or tablets, are used. Some people with aniridia are able to be successfully stablise eye pressure using medication. The medications used are

Miotics - these cause the cillary body muscles to constrict, opening up the angle between the iris and the trabecular meshwork.



Carbonic anhydrase inhibitors

The second option is surgery.

There are three surgerical proceedures that may be used to stablise eye pressure.

Trabeculectomy - In this proceedure a small segment of the trabecular meshwork is removed. This allows the aqueous humour to drain away. This proceedure is more commonly used on individuals with congential glaucoma, and is not very successful in secondary aniridic glaucoma.

Cyclocryotherapy - In this proceedure part of cillary body (this includes the iris and the set of muscles that surround the lens) is frozen to stop it producing too much aqueous humour. This is often needed more than once and can have serious complications, therefore this is usually used as a last result.

Tube Implant- In this proceedure a tube is place in the sclea (the white of the eye). to provide an alternative drainage system. This is the most affective proceedure for people with aniridic glaucoma in a study conducted at King Khaled Eye Specialist Hospital, Riyadh, Kingdom of Saudi Arabia by R. E. Wiggins Jr and K. F. Tomey found that the Molteno implant was successful in 83% of the eyes in which the proceedure was used. the success of drainage devices has proven to be successful in patients with aniridic glaucoma in other studies.

What can go wrong?

The long term use of medication for aniridic glaucoma is not thought to be affective. Eventually surgery may be required.

The anti-glaucoma surgery has high risks in aniridia. The aniridic eye is fragile and because of this any surgery may cause further complications of aniridia.

The lens and the muscles about the lens may be distrubed causing cataracts, dislocation of the lens or both.

The vitreous humour may be distrubed and if this happens a vitreous detachment may cause flashes and floaters, and in some cases it may lead to a retinal detachment.

The surgery may induce the progression of Aniridic Keratopathy.

In general the antiglaucoma sergery may not work and eye pressure may remain high.