chronIc open angle glaucoma (coag) is a progressive disease in which a degenerative process takes place in the trabecular meshwork of the eye, with deposition of extracellular material in the meshwork and beneath the endothelial lining of Schlemm’s canal (riordan-eva and Whitcher 2007). It is a common and potentially blinding condition, and is usually asymptomatic until advanced (national Institute for health and clinical excellence (nIce) 2009). once diagnosed, older people with coag require lifelong monitoring so that any progression of visual damage can be detected. controlling the condition to prevent or minimise further damage is crucial to maintaining sight (nIce 2009).
approximately 10 per cent of blindness registrations in the uK are attributed to glaucoma (nIce 2009). around 2 per cent of people over the age of 40 have coag, rising to almost 10 per cent in people aged over 75. There are 480,000 people affected by coag in the uK, and more than a million glaucoma-related hospital outpatient visits each year (nIce 2009).
Drainage angle The drainage angle is formed by the iris and cornea (figure 1, page 20). The anterior chamber lies behind the cornea and in front of the iris. The posterior chamber lies between the iris, lens and ciliary body (James et al 2007). aqueous humour is present in both chambers and vitreous humour exists in the vitreous cavity.