Glaucoma is a progressive disease of the optic nerve caused when the pressure inside the eye is higher than the optic nerve can withstand. The most common form of glaucoma will cause a patient to slowly lose their vision, starting with their peripheral vision. For many years this loss of vision will go unnoticed by a patient. Left untreated, glaucoma will result in blindness. According to W.H.O. glaucoma is the second most common cause of blindness after cataracts worldwide.