Surgical outcomes of different Ahmed Glaucoma Valve implantation methods between scleral graft and scleral flap

Abstract

Purpose: To compare the surgical outcomes of the two different methods used for Ahmed Glaucoma Valve (AGV) implantation between the donor scleral graft method and the partial-thickness scleral flap method.

Methods: We retrospectively reviewed medical records of 28 eyes of 26 patients diagnosed as neovascular glaucoma followed by AGV implantation. Based on the surgical method, the included eyes were divided into two groups. In the graft group (n = 18), the drainage tube was inserted into the anterior chamber, and then covered with preserved donor sclera. In the flap group (n = 10), the drainage tube was inserted under the partial-thickness scleral flap, and then covered with the flap. We compared the postoperative intraocular pressure (IOP), surgical success rates, and postoperative complications between the two groups.

Results: Postoperative IOP was not significantly different between the two groups (p = 0.967, 0.495 at 12 months, 24 months, respectively, by the Mann-Whitney U-test). The mean success periods were 53.1 ± 10.1 months in the graft group versus 50.9 ± 9.4 months in the flap group (p = 0.882 by log rank test), and cumulative success rates were 77.8% and 80.0% at one year, respectively. However, tube migration occurred more frequently in the flap group than in the graft group (p = 0.037 by Fisher's exact test).

Conclusions: In AGV surgery for neovascular glaucoma, the scleral graft method may be associated with relatively less complication about tube migration than the scleral flap method. The surgical results, however, were not statistically different.

Keywords: Ahmed Glaucoma Valve; Scleral flap; Scleral graft; Surgical complication.

Fig. 1

The baseline and postoperative intraocular pressure (IOP) measurements in the graft group and flap group. Only at six months postoperatively did the graft group have a significantly lower mean IOP compared to the flap group (indicated by an asterisk, p = 0.006 by Mann-Whitney U-test). After that time, postoperative IOP values were not significantly different between the two groups (p-values by Mann-Whitney U-test were 0.967, 0.287, and 0.495 at 12 months, 18 months, and 24 months, respectively). Preop = preoperative.

Fig. 2

The cumulative survival graph was determined by the Kaplan-Meier method, and the success rate was compared using the log rank test. The cumulative success rates were 94.4% versus 90.0% at six months and 77.8% versus 80.0% at one year in the graft and flap groups, respectively. The success rates were not significantly different (p = 0.882 by log rank test).