Glaucoma refers to a group of conditions that lead to damage of the optic nerve head, typically caused by raised intra-ocular pressure. Primary open angle glaucoma is the commonest glaucoma type in the UK and affects 8% of people at 80 years old. In open angle glaucoma the iridocorneal angle is open but aqueous flow is diminished. As glaucoma progresses, it can lead to peripheral visual field loss. The mainstay of treatment initially is with eye drops with the aim of lowering intraocular pressure. Intraocular pressure is determined by the production, circulation and drainage of aqueous humour and is considered normal if between 11-21mmHg. If treated, glaucoma progression can be delayed and most people will not have severe visual impairment.