Glossary

Aqueous

The space between the lens and the cornea is filled with a clear watery fluid called aqueous humour. It is the balance between the production and drainage of aqueous humour that controls the level of pressure within the eye (the intraocular pressure).

Aqueous humour is produced behind the iris by the ciliary body. It flows through the pupl and drains away through the trabecular meshwork (and back into the blood stream vis schlemm's Canal) at the angle between the cornea and the iris (the drainage angle).

Most of the aqueous humour drains away via this route and this is known as the conventional pathway.

However, some aqueous humour also leaves the eye through the ciliary body and this is called the uveo-scleral or non conventional pathway.

In both chronic and acute angle closure glaucoma the conventional pathway is restricted because the iris has blocked the drainge angle of the eye, the difference being largely in the rate of rise in the intraocular pressure. Chronic simply means slow and Acute means fast.

In lens induced glaucoma, an increase in the size of the lens (because of some types of cataract formation) pushes the iris forward so that it restricts the conventional pathway leading to a rise in intraocular pressure. The treatment in this case is to remove the natural lens and to replace it with an intraocular lens implant (a cataract operation).

In neovascular glaucoma (or rubeotic glaucoma) new blood vessels growing over the surface of the iris block the conventional outflow pathway.

In developmental glaucoma (buphthalmos) the trabecular meshwork has failed to develop in the normal way and may even be covered by a fine membrane. Such cases will usually require surgery to protect the vision of the baby.