glaucoma

Your optic nerve carries information from light sensitive areas in your eye to your brain. It here that it is perceived as a picture. Glaucoma is the name of a group of eye conditions where the optic nerve is damaged at the point where it leaves the eye.

To keep the eye ball in shape the eye

needs a certain amount of pressure. If the optic nerve (the green circle in the image) comes under too much pressure then it can be damaged depending on how much pressure occurs, how long it lasts and whether there is poor blood supply or other weakness to the optic nerve. Excessively high pressure can damage your optic nerve immediately. Low levels of pressure cause damage more slowly and you could gradually lose your sight if it went untreated.

There are four main types of glaucoma:

• Chronic glaucoma – most common, eye pressure rises slowly and there is no pain to highlight the problem
• Acute glaucoma – occurs when there is sudden blockage. This can be quite painful and cause damage to sight if not treated promptly
• Secondary glaucoma – when a rise in pressure is caused by other eye conditions
• Developmental glaucoma – a malfunction of the eye in babies

Risk factors include:

• Age: becomes more common with increasing age. It is rare under 40, but affects 1% of people over 40 and 5% of people over 65
• Race: occurs more frequently and severely in people of African origin
• Family: people with glaucoma in their family are more likely to get it themselves
• Short sightedness: people with short sight are more likely to develop glaucoma
• Diabetes: is believed to increase the risk of glaucoma

Early signs of sight loss related to glaucoma usually occurs in the shape of an arc above and below the centre of your vision when you look straight ahead. If left untreated this will spread outwards and inwards leading to what is known as ‘tunnel vision’.

Treatment aims to reduce or increase pressure in the eye and improve blood supply to the optic nerve.

More detailed information can be found at the RNIB website.