Otago glaucoma surgery outcome study: long-term results of trabeculectomy--1976 to 1995.

OBJECTIVE: To provide data on the long-term results of trabeculectomy performed in the province of Otago, New Zealand.

DESIGN: Retrospective noncomparative case series.

PARTICIPANTS: A total of 289 eyes of 193 patients (excluding 4 eyes lost to follow-up soon after operation); all trabeculectomies performed for the first time on cases of primary glaucoma from 1976 through 1995.

INTERVENTION: Standard Cairns trabeculectomy.

MAIN OUTCOME MEASURES: Intraocular pressure, visual acuity, visual field damage.

RESULTS: Trabeculectomy was effective in controlling intraocular pressure at a level of 21 mmHg or less, with probabilities of 0.93 (95% confidence interval [CI], 0.90-0.97), 0.87 (95% CI, 0.82-0.93), and 0.85 (95% CI, 0.77-0.92) at 5, 10, and 15 years, respectively, after surgery. The mean visual acuity improved from 20/60 to 20/40 immediately after trabeculectomy but then declined steadily over the postoperative years. The decline in visual acuity led to blindness in 47 eyes. The Kaplan-Meier estimated probability of retaining useful vision (visual acuity > 20/400 and visual field > 5 degrees radius) in the overall group was 0.87 (95% CI, 0.79-0.91), 0.72 (95% CI, 0.60-0.79), and 0.6 (95% CI, 0.43-0.69) at 5, 10, and 15 years, respectively, after surgery. Those eyes that had good preoperative visual acuity (visual acuity > or = 20/30) had a significantly better chance of retaining useful vision (P = 0.02).

CONCLUSIONS: The intraocular pressure was well controlled by trabeculectomy, but a steady long-term decline in visual acuity and visual field occurred, decreasing the probability of an eye retaining useful vision up to the time of death to approximately 0.6.