Glaucoma is a type of disease that causes high pressure fluid to build up within the eye, causing damage to the optic nerve. This type of damage can be irreversible, causing poor eyesight and sometimes blindness. Acute Glaucoma causes the pressure in the eyes to rise quickly to very high levels and patients experience sudden severe eye pain, blurred vision and headaches. Chronic Glaucoma however tends to develop at a much slower rate, not showing any symptoms at the beginning. As the nerve damage becomes more severe, vision becomes affected and most patients experience 'tunneling'. Some individuals eventually become fully blind.