Glaucoma filtering surgery: factors that determine pressure control.

Factors that determine pressure control after filtering surgery were studied in 194 eyes of 158 patients in a retrospective study. Emphasis was placed on the cumulative probability method of Kaplan and Meier and multiple regression analysis. Aphakia and the presence of a surgical bleb were the most important factors. Age and type of surgical procedure were next. Race and race-sex interaction were the least important. The above factors accounted for only 6% to 16% of the total variance. The difference between eyes of the same patient was less than that between paired eyes of different patients but the former was surprisingly high. In the selected group of successful cases without medication the postoperative pressure was independent of the baseline pressure and choice of surgical procedure.