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.