Purpose: To determine the long term outcome of
glaucoma filtration surgery in preserving
vision.
Methods: A retrospective, community-based, study of residents of Olmsted County,
Minnesota who underwent filtration surgery between 1965-1998.
Results: 73 eyes of 49 patients underwent routine filtration surgery. Analysis
of the first eye having surgery revealed a mean preoperative intraocular
pressure 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.
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.