Patients diagnosed with glaucoma usually undergo visual field testing at regular intervals to assess optic nerve function. Depending on the severity and rapidity of progression of existing damage, visual field testing may be required as often as every 1 to 4 months, decreasing in frequency as stability of the visual field and optic nerve head appearance are demonstrated. This slide shows a printout of one patient’s visual field test results over several years. Note the progressive enlargement of the scotoma (the dark areas), where vision is subnormal or absent.