Combined Glaucoma Tube Shunt (Ahmed) and Fluocinolone Acetonide (Retisert™) Implantation Compared to Ahmed Alone in Uveitic Glaucoma

Introduction Glaucoma is a known complication of uveitis, and may require glaucoma tube shunt implantation for intraocular pressure (IOP) control. The success of glaucoma tube shunt implantation in the setting of a local ocular steroid depot in uveitic glaucoma remains unknown. The purpose of this study was to determine whether patients who underwent combined glaucoma tube shunt (Ahmed) and fluocinolone acetonide (Retisert™, Bausch + Lomb, Bridgewater, NJ, USA) implantation have superior outcomes compared to patients with Ahmed implants only in the setting of uveitic glaucoma. Methods All participants were studied retrospectively and underwent Ahmed implantation alone or with existing/concurrent Retisert implantation (combined group) at a single academic institution. The main outcome measures were IOP, visual acuity (VA), number of IOP-lowering medications, and adverse events at 6 months after Ahmed implantation. Secondary outcome measures included adverse events and surgical success at 6 months after Ahmed implantation. Results Mean IOP at 6 months after Ahmed implantation was 15.3 ± 4.8 and 15.1 ± 4.9 mm Hg in the Ahmed only group (n = 17) and the combined group (n = 17), respectively (p = 0.89). The mean number of IOP-lowering medications at 6 months after Ahmed implantation was 1.7 ± 1.0 and 1.8 ± 1.0 in the Ahmed only group and the combined group, respectively (p = 0.86). Mean VA at 6 months after Ahmed implantation was 0.35 ± 0.29 and 0.42 ± 0.33 log mean angle of resolution in the Ahmed only group and the combined group, respectively (p = 0.50). No significant differences in surgical success or adverse events were noted between the two groups. Conclusion At 6 months, no significant differences in mean IOP, mean number of IOP-lowering medications, VA, surgical success, or adverse events were noted between Ahmed implantation alone or combined Ahmed and Retisert implantation in patients with uveitic glaucoma.


INTRODUCTION
The Ahmed glaucoma tube shunt, introduced in 1993 [1], is used in the management of elevated intraocular pressure (IOP) and glaucoma [2,3]. The Ahmed design incorporates a flow restrictive device, thus reducing the incidence of postoperative hypotony [4] and making the Ahmed of particular utility in uveitic glaucoma [5]. After Ahmed implantation, the device progresses through predictable phases, including a hypertensive phase coinciding with encapsulation and bleb formation over the Ahmed plate. This phase is generally associated with an increase in IOP to greater than 21 mmHg [6]. Excessive inflammatory response after Ahmed implantation appears to be associated with higher failure rates and elevated IOP [7,8].
Studies have demonstrated the importance of permeability of the capsule overlying the Ahmed plate in determining the long-term control of IOP [9,10]. Anti-inflammatory agents have been shown to be associated with thinner-walled capsules and lower IOP in certain patient populations [11,12]. Indeed, recent studies using long-term topical steroid tapers, as well as aqueous suppressants after Ahmed implantation appear to show a reduction in the degree of IOP elevation during the ocular hypertensive phase, as well as an improvement in the long-term IOP control [13].

Study Design and Outcome Measures
For both the groups, the data were collected immediately prior to Ahmed implantation and at the following time intervals after Ahmed

Intraocular Pressure
After Ahmed implantation, both the Ahmed only and combined Ahmed and Retisert groups had a significant reduction in mean IOP on postoperative day 1 (Fig. 1). The initial reduction in IOP immediately after

Visual Acuity
Immediately after Ahmed implantation, a trend towards worsening VA was noted in both the Ahmed only and the combined Ahmed and Retisert groups (Fig. 3). However, the VA in both the groups trended towards an improvement, and reached levels similar to baseline VA prior to Ahmed implantation (Fig. 3). The VA at  (Table 1).

Systemic Immunosuppression and Active
Inflammation Post-Ahmed implant systemic immunosuppression was required in a larger proportion of eyes in the Ahmed only group (52.9, 43.8, and 35.7% at 1, 3, and 6 months, respectively) relative to the combined Ahmed and Retisert group (11.8, 6.2, and 6.7% at 1, 3, and 6 months, respectively). This difference was statistically significant at 1 and 3 months, but not at 6 months (p B 0.01, 0.01, and 0.06,

Surgical Success
Using the Kaplan-Meier survival analysis, there appeared to be a trend towards higher surgical success in the combined Ahmed and Retisert group relative to the Ahmed only group, however, we found no statistically significant difference in the duration of surgical success between the two groups (p = 0.32, Fig. 4 without Retisert implantation, which found no significant difference in the long-term IOP control between these two groups [14]. However, Moore et al. found that the duration of surgical success (defined as IOP between 5 and 18 mm Hg and greater than 20% reduction of IOP at two consecutive visits without loss of light perception, or need for additional IOP-lowering surgical procedures) was significantly greater in the combined Ahmed and Retisert group when compared to Ahmed alone [14].