Abstract
Purpose :
The XEN gel stent and Ahmed valve are both designed to prevent postoperative hypotony. We performed a retrospective study to compare the efficacy of these devices.
Methods :
Patients who had either XEN gel stent or Ahmed valve surgery were screened and those with primary open angle glaucoma (POAG) were identified for further analysis. Patients with low-tension glaucoma, a complicated ocular history, and/or prior glaucoma surgery were excluded. The final study population had 41 eyes from 37 patients with 21 XEN gel stents and 20 Ahmed valves. Pre- and postoperative intraocular pressures (IOP) at day 1 (POD1), week 2 (POW2), and month 1 (POM1) were recorded. We defined hypotony as an IOP < 6.5 mmHg within the first postoperative month. The primary outcome was the rate of hypotony. Secondary outcomes were the mean IOP at each postoperative visit and the rate of short-term failures (defined as an IOP > 21 mmHg at the POM1 visit).
Results :
Baseline characteristics were comparable between the XEN gel stent and Ahmed valve groups. At the POD1 visit, hypotony rates were 19.0% and 5.0% for the XEN and Ahmed valve groups, respectively. At the POW2 visit, hypotony rates were 4.8% and 10.5% for the XEN and Ahmed valve groups, respectively. By the POM1 visit, postoperative hypotony had resolved in all eyes in both groups. The differences between the rates of postoperative hypotony of each group were not statistically significant at the specified postoperative visits [p=0.154 (POD1), p=0.494 (POW2), p=N/A (POM1) as there were no cases of hypotony by POM1]. The differences between the mean IOP at each postoperative visit were not statistically significant between the two groups [p=0.887 (POD1), p=0.266 (POW2), p=0.211 (POM1)]. Short-term failures occurred in 23.8% of eyes in the XEN group and there were no short-term failures in the Ahmed valve group.
Conclusions :
Both the XEN gel stent and Ahmed valve devices effectively decrease IOP and reduce the risk of early postoperative hypotony in patients with uncontrolled POAG. Any cases of postoperative hypotony were transient and resolved by POM1. Interestingly, all short-term failures occurred in the XEN group and in African American patients only. Additional studies can be performed to determine potential contributing factors.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.