Glaucoma occurs when pressure in the eye damages the optic nerve connecting the eye to the brain. This can lead to permanent visual loss. Glaucoma is the leading cause of preventable irreversible blindness worldwide. In Australia it effects 2% of adults over 40 and 10% older than 80. Risk is greater for those with glaucoma in the family. Glaucoma mostly progresses slowly and affects peripheral vision first. In early glaucoma peripheral visual loss is often unnoticed. This is why glaucoma does not usually cause symptoms until it reaches a late stage in the disease. If detected early, glaucoma can be treated by lowering the eye pressure. This slows down or halts the progression of the disease. However, if detected too late, damage to the optic nerve from glaucoma cannot be undone.