Is Intraocular Pressure in the Early Postoperative Period Predictive of Antimetabolite-Augmented Filtration Surgery Success?

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Purpose:To determine whether intraocular pressure (IOP) in the early postoperative period after trabeculectomy or combined phacoemulsification-trabeculectomy, augmented with antimetabolite, correlates with IOP at one year in surgeries considered to be successful at that time point.Design:Retrospective case series.Methods:A chart review of antimetabolite-augmented surgical procedures done by DJG and JBS between January 1994 and November 2000 identified 82 primary or secondary trabeculectomies and 53 combined phacoemulsification-trabeculectomies with at least one year of follow-up. The success rate for each surgical subgroup was calculated and IOP on postoperative days (POD ± SD) 1, 7 (±2), 30 (±5), 90 (±10), and 180 (±20) was correlated with IOP at one year (POY 1, between month 12 and 15) using linear regression. IOP at each time point was compared among eyes that achieved success at one year with and without the use of IOP-lowering agents.Results:Of the 82 eyes having undergone antimetabolite-augmented trabeculectomies and the 53 eyes having undergone combined surgeries with at least one year of follow-up, the surgical success rates at POY 1 were 87.8% (72 of 82 eyes) and 92.5% (49 of 53 eyes). Of these, 42 eyes (58.3%) from 39 patients in the trabeculectomy group and 27 eyes (55.1%) from 24 patients in the combined surgery group did not require glaucoma medications at one year postsurgically, and were considered complete surgical successes. Mean preoperative IOP mm Hg ± SD was 26.0 ± 8.5 for the trabeculectomy group and 18.2 ± 4.5 for the phaco-trabeculectomy group. Postoperative IOP at POD 1, POD 7, POD 30, POD 90, POD 180, and POY 1 respectively for the eyes undergoing trabeculectomy were 13.9 ± 10.4, 9.5 ± 6.2, 12.0 ± 5.5, 12.0 ± 5.2, 12.8 ± 5.9, and 12.1 ± 4.3, and for the combined surgery group were 20.8 ± 12.5, 9.7 ± 5.7, 12.2 ± 5.4, 11.1 ± 3.4, 11.6 ± 4.6, and 10.3 ± 4.3. Intraocular pressure on postoperative day one correlated poorly with intraocular pressure at POY 1 for the trabeculectomy group (R2 = 0.0788), and not at all for the combined procedures group (R2 = 0.018). The correlation was slightly better for intraocular pressure at postoperative day 90 for the trabeculectomy group (R2 = 0.546), and at postoperative day 180 for the combined group (R2 = 0.37), but still rather low. Eyes requiring glaucoma medication use at POY 1 in the trabeculectomy group had higher (P < 0.009) intraocular pressure at POD 30 and at all subsequent visits than eyes not requiring these medications. Eyes requiring glaucoma medication use at POY 1 in the phaco-trabeculectomy group had higher (P < 0.0025) intraocular pressure at POD 30, POD 180, and POY 1 than eyes not requiring these medications.Conclusion:Intraocular pressure in the early postoperative period correlates very poorly with intraocular pressure one year after successful antimetabolite-augmented trabeculectomy or combined cataract extraction and trabeculectomy. Starting one month after glaucoma surgery, intraocular pressure is substantially lower in eyes that will ultimately not require the use of ocular hypotensive agents to achieve clinical success one year postoperatively.

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