Glaucoma affects your peripheral vision. Treatment aims to slow the rate at which the peripheral vision deteriorates. In many people, this process is slow and the process takes 10 to 25 years to cause patients serious visual disability. But in an unfortunate few, peripheral vision deteriorates rapidly over months. Unfortunately, it is not always possible to predict which category a particular patient falls into.

We know that the level of intraocular pressure (IOP) is important, but this needs to be interpreted in conjunction with a knowledge of the corneal thickness and the state of the optic disc. Long-term IOP fluctuation has also recently been recognised as an independent risk factor.

After peripheral vision has been severely affected, central vision may also deteriorate, although a recent study suggested that it was very rare for patients to go completely blind.