There are several different types of glaucoma but they all result in damage to the vision by the loss of nerve fibres in the optic nerve which connects the eye to the brain. The commonest type of glaucoma is called primary open angle glaucoma or POAG.
In POAG the pressure in the eyeball is too high and this causes damage to the nerve at the back of the eye which results in patches of missing vision. Without treatment the missing bits of vision enlarge and may eventually, after a period of several years cause severe loss of vision. Fortunately the pressure in the eye can be lowered using eye drops, laser treatment or surgery.
In the vast majority of cases this will be enough to prevent significant loss of vision. Early detection of glaucoma allows treatment to start before much vision has been lost. This is important as it is not possible to repair the damage to the nerve and vision once it has happened. Glaucoma is one of the conditions your optician or eye specialist will check you for. The glaucoma check involves measuring the pressure in the eye, examining the optic nerve and in some cases performing a visual field test. Photographs or OCT imging of the optic nerve may also be helpful.
Most people are not aware that they have suffered any visual field loss from glaucoma, particularly at the early stages. Unfortunately when you have glaucoma the visual field loss can sometimes be enough to prevent you from driving legally even if you think your vision is normal. If you have glaucoma in both eyes you must, by law, inform the driving licence authority about your condition and a specific visual field test called a binocular Esterman field can be performed to see if you are still legal to drive. Because early glaucoma has no symptoms and early treatment prevents blindness it is important to have regular eye checks with your optician. A free annual glaucoma check is available to anybody over the age of 40 by their optician if they have a 1st° relative who is known to have glaucoma.
In this condition the eye pressure is higher than normal (as in glaucoma) but there is no evidence of damage to the nerve or visual field. Some patients with OHT will go on to develop glaucoma. If you have OHT your eye specialist can monitor your eyes and decide whether it is necessary to go on to treatment to prevent glaucoma developing.
International Glaucoma Association: www.glaucoma-association.com
Driving and Vehicle Licensing Agency: www.dvla.gov.uk