Bright Sight

Oliver Backhouse, Consultant Eye Surgeon www.cataract.org.uk

Glaucoma and Uveitis

Production and drainage of fluid inside the eye keep the eye at a particular pressure and shape. The circulation and drainage of this fluid can be disturbed by inflammation inside the eye. If the pressure slowly increases over a long period of time it can cause painless damage to vision. This condition is called chronic glaucoma. Occasionally steroid eye drops, used to treat the uveitis, causes a pressure rise but more often it reduces the pressure by controlling the inflammation. A much less common form is acute glaucoma where the pressure rapidly increases. This usually causes pain and blurred vision and needs to be treated urgently.

The Diagnosis of Glaucoma:

Measuring the pressure inside the eye is a routine part of an eye examination and will be performed at most visits. For this reason glaucoma is usually detected early in patients with uveitis before it has caused significant damage. An estimate of the damage caused is made by looking inside the eye at the optic nerve (the ‘wire’ that takes the message of sight from the eye to the brain). A visual field test will show any small changes to the vision that are characteristic of glaucoma.

The Prevention of Glaucoma:

A. Treating the inflammation.
In uveitis, the inflammation and scarring caused by the uveitis is the usual cause of glaucoma. Keeping the inflammation down to a minimum is therefore a priority and severe inflammation must be treated vigorously with either eye drops or other treatments.

B. Preventing scars from forming.
Uveitis has a particular tendency to cause the iris (coloured part of the eye) to stick to the lens behind it. The fluid inside the eye has to circulate through the pupil (black hole in the middle of the iris). If the pupil becomes completely stuck to the lens it will cause acute glaucoma. To try and prevent these adhesions, dilating drops such as Atropine, Cyclopentolate or Tropicamide are used. All of these drops cause the vision to be blurred while being used.

The Treatment of Glaucoma:

A. Eye Drops.
These usually work by reducing the amount of fluid being made by the eye and are used mostly twice a day. In this way pressure can be kept down to a normal level. There are many different drops and two examples are Timolol (Timoptol) and Dorzolamide (Trusopt). The drops are put in regularly and may need to be used for a long time.

B. Tablets.
Acetazolamide (Diamox) may be needed to help control the eye pressure. Common side effects are tingling fingers, tiredness and loss of appetite. Its use is usually temporary.

C. Laser Treatment.
In some circumstances this is the best method to control the pressure but is only undertaken if medical treatment is not adequate.

D. Glaucoma Surgery.
If pressure control is poor surgery may be advised. A controlled ‘trapdoor’ is made on the white of the eye (sclera) under the upper eyelid. This allows some of the fluid inside the eye to seep out thereby lowering the pressure. A ‘bleb’ forms under the eyelid due to the collection of the seeping fluid under the skin of the eye surface (conjunctiva).

In no patient can a trabeculectomy be guaranteed to be successful. Patients with uveitis have a greater rate of failure as the inflammation tends to scar and block the small trapdoor, preventing fluid from escaping. For this reason an ‘anti-scarring drug’ may be used on the white of the eye during and after the operation at outpatient follow-up visits.

No operation is entirely without risk. Rarely, problems with the anaesthetic (either local or general) can be dangerous to life. Uncommonly an infection develops inside the eye after the operation. This, and other rare complications, can make vision worse after the operation than it was before. It is not uncommon to develop a cataract at some time after a glaucoma operation, especially in patients with uveitis.

Disclaimer: Adapted from Manchester uveitis patient leaflet.