There is no known physiological cause of glaucoma other than increase in pressure inside the eye. A significant percentage of the people for whom the eyedrop treatment has been prescribed fail to follow the prescribed daily regimen, because the eyedrops have unpleasant side effects. Doctors rarely recommend the surgery for glaucoma patients who have already started the traditional course of treatment. The eyedrops traditionally prescribed to treat glaucoma are normally prescribed to treat other disease of the eye.
Although initially symptomless, glaucoma can eventually cause blindness when not properly treated. Tests under laboratory conditions of the traditional treatment, daily administration of eyedrops, show it to be as effective in relieving the internal ocular pressure that causes glaucoma as is a new laser-surgical procedure. Yet glaucoma-related blindness occurs in a significantly smaller percentage of patients who have had the surgery than of patients for whom only the eyedrop treatment was prescribed.
Which of following, if true, most helps to explain the low rate glaucoma-related blindness among patients who had the surgery?