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The long-term outcome of glaucoma filtration surgery
C E Parc1, D H Johnson, J E Oliver
1Department of Ophthalmology, Mayo Clinic, and Mayo Foundation, Rochester, Minnesota 55905, USA.
Purpose:
To determine the long-term outcome of glaucoma filtration surgery in preserving vision. Visual loss from progressive glaucomatous damage and from complications of surgery, both short and long term, were included.
Methods:
A retrospective, community-based, longitudinal study of residents of Olmsted County, Minnesota, who were newly diagnosed with open-angle glaucoma between 1965 and 1980 and underwent filtration surgery in these or subsequent years through 1998. Intraocular pressure (IOP), visual acuity, visual fields, and progression to legal blindness were monitored. Kaplan-Meier analysis was used to determine the cumulative probabilities of changes in these parameters.
Results:
73 eyes of 49 patients underwent conventional filtration surgery. Analysis of the first eye having surgery revealed a mean preoperative IOP of 27.6 +/- 8.5 mm dropping to 16.7 +/- 5.6 mm at year one, and remaining in this range throughout follow-up (14.7 +/- 3.0 mm at 10 years; with or without use of medications). The probability of progression to blindness was 46% at 10 years after surgery, as calculated by Kaplan-Meier analysis. Eyes going blind had a postoperative IOP equal to or lower than those not becoming blind (14.0 +/- 4.4 vs. 15.4 +/- 3.0 at postoperative year 10). Eyes going blind had more advanced field loss at the time of surgery, with scotomas above and below the horizontal axis, than eyes not going blind, which had scotomas in only one hemifield. Three patients developed late bleb leaks; two patients developed endophthalmitis. The probability of undergoing cataract surgery was 37% by 10 years postoperatively, which did not differ significantly from the cohort of patients not undergoing surgery at a comparable time point.
Conclusions:
Filtration surgery was associated with a 54% probability of preservation of vision from progression to legal blindness at 10 years after surgery. Patients becoming blind had more advanced field loss at the time of surgery; IOP was similar between those going blind and those retaining vision.