Cutting Edge Glaucoma - Issue 2

TWO-YEAR RESULTS OF A MULTICENTER STUDY OF THE AB INTERNO GELATIN IMPLANT IN MEDICALLY... • 41  as trabeculectomy [39–41], but is a much less invasive procedure and provides a more controlled outflow; these factors likely explain the lack of differences between the two groups observed in our study. How the effectiveness of the trabecular micro-bypass stent compares with that of the gelatin implant remains to be determined because the primary and secondary outcomes in studies of the trabecular micro-bypass stent assessed IOP lowering from unmedicated/washed-out baseline [10, 30]. In our study, eyes did not undergo washout before surgery, so the baseline IOP was expectedly lower. Also, most patients included in this study had moderate POAG, with an average visual field mean deviation of − 8.0 dB, compared with − 3.9 dB in the trabecular micro-bypass study [10, 30]. In studies of trabeculectomy, the gold standard for filtering surgery in open-angle glaucoma, effective IOP lowering to low teens was reported, but this was associated with significant AEs. Although the Tube versus Trabeculectomy study did not report outcomes at 2 years, results at 1 [42] and 3 years [43] showed that 57 and 60% of patients in the trabeculectomy arm experienced postoperative complications, respectively, compared with 29.8% at 2 years in our study. In a ret- rospective study that evaluated the outcomes and risk factors for failure of the gelatin stent versus trabeculectomy [24], both procedures had a 75% survival of approximately 10 months without medications or additional surgery (complete success) and > 2 years with add-on medications or laser trabeculoplasty (qualified success). Notably, one quarter and one third of eyes treated with the gelatin stent and trabeculectomy, respectively, were receiving glaucoma medications at the last recorded visit [24]. In line with the increasing trend of subconjunctival injection of MMC in trabeculectomy, all eyes implanted in this study received subconjunctival antifibrotic injection (range: 10–80 μg for MMC; two patients received 500-μg 5-FU) to allow precise dosing, compared with the traditional sponge method [44, 45]. The study thus adds to the prospective data on the perioperative admin- istration of MMC by subconjunctival injection with implantation of the gelatin stent, at dosages aligned with expert recommendations (10–40 μg) [46]. The device exhibited an acceptable safety profile. All cases of hypotony (defined as IOP < 6 mmHg) were self-limited and self-resolved within 1 month of surgery, similar to what was reported by Grover et al . [23]. Low IOP in the immediate postimplantation period seems less likely to lead to clinical hypotony-related complications, compared with similar IOP after trab- eculectomy, and thus may be amenable to observation without immediate intervention [8, 47]. Although SAEs were rare during the 2-year study, the isolated case of endophthalmitis under- scores the need for ongoing care and monitoring of patients following glaucoma filtering proce- dures, even when IOP is well controlled post-surgery. Potential study limitations include some variability in the perioperative regimens, which may have impacted the study outcomes. Current recommendations from surgeons experienced with the gelatin stent suggest that preoperative preparation of the conjunctiva and ocular surface, placement closer to the 12 o’clock position, avoiding penetration of Schlemm’s canal during implantation, making sure that the implant is free and mobile under the conjunctiva at the end of surgery, and achieving specific target IOP on day 1 or a low week-1 delta IOP, among others, may help optimize outcomes; most, however, were not published and thus not implemented during