Visual prognosis in advanced glaucoma: a comparison of medical and surgical therapy for retention of vision in 101 eyes with advanced glaucoma.

A detailed analysis of 101 eyes of 76 patients with advanced glaucomatous visual field loss but with retention of good visual acuity is presented. Patients were followed for a minimum of 4 years with an average duration of follow-up of 7.1 years. Loss of central vision, defined by permanent reduction of visual acuity to less than or equal to 20/200, occurred with equal frequency in eyes treated medically (15.8%) or surgically (13.6%) for glaucoma. Sudden loss of central vision also occurred following cataract extraction (8.7%). No patient lost central vision suddenly following surgery when central vision was spared at the time of operation. In addition, all cases that eventually lost central vision, either medically or surgically, demonstrated field defects which split fixation prior to its loss. Loss of central vision is seen rarely when medical therapy maintains the average intraocular pressure below 18 mm Hg, but increases markedly with higher pressures, reaching approximately 30% when average intraocular pressure is above 22 mm Hg. Progression in field loss is rare after successful glaucoma surgery, although cataracts develop in about 32% of such eyes. Cataracts also develop in 21% of medically treated eyes. In addition, about 50% of unoperated eyes demonstrate further field loss even when central vision is maintained. In spite of very definite risks, serious consideration should be given to glaucoma filtering surgery when the intraocular pressure is consistently over 22 mm Hg in patients on medical therapy with advanced glaucoma.