Long gone are the days where glaucoma surgery meant an invasive procedure with the likelihood of a serious complication developing down the road – while trabeculectomy is still a viable option, its side-effect profile is relegating it to more of a final option. These days, surgeons are much more likely to recommend minimally invasive glaucoma surgery (MIGS) long before patients are on maximum medical therapy.
At this year’s American Glaucoma Society meeting, E. Randy Craven, MD, stressed clinicians need “to move our concept of success away from drug freedom to realizing low pressures comparable to what we are used to with trab – however achieved – is a success. If I can implant one MIGS device and get the patient down to one drop over the long term, that’s a success.”
Dubbing this concept “MIGS and Meds,” Dr. Craven expects the MIGS side of things to expand by year’s end with the anticipated approval of Transcend Medical’s CyPass microstent and shortly thereafter Ivantis’ Hydrus microstent (called an intracanalicular scaffold). Glaukos’ iStent has hit maturity, and the company’s iStent Supra is showing promise as well. Outside the US, Allergan/AqueSys’ Xen gel stent, a permanent, soft, collagen-derived gelatin, has the CE mark, and is under investigation in the US.
Dr. Craven has personally implanted the iStent in five different countries, and in some developing countries where microscopes are not as advanced as they are in the US, “surgeons have a hard time getting a good view for placement of the iStent,” he said. “That’s a potential limitation with global expansion of these devices.”
Davinder S. Grover, MD, MPH, reported on the first 975 eyes implanted with the Xen. Three different lumen sizes (140, 63, and 45 μm) were implanted over the course of the three-year study in 12 countries; patients were followed from three to 36 months. The surgery was performed as a stand-alone procedure or in conjunction with phaco; multiple generations of injectors were used during the study period as well. The mean preop medicated intraocular pressure (IOP) was 21.9 mmHg, and patients were on an average of 2.6 medications. At month 36, the mean IOP had dropped to 13.2 mmHg, a 39.8% decrease, and the number of meds dropped to 0.7. Complications were minor, with implant blockage occurring in 1.8%, secondary surgical procedure related to the Xen occurring in 2.3%, secondary surgery not related to the Xen occurring in 1.2%, and hyphema occurring in 1.9%. Longer-term follow-up is ongoing in both US and European studies, particularly with the Xen 45 group.
Rohit Varma, MD, presented on the European study (n=25 in the Xen 63 group and n=43 in the Xen 140 group). At month 36, the mean IOP had dropped to 13.5 mmHg, a 39.7% decrease from the baseline of 23.3 mmHg, and the number of meds dropped to 0.6 from 2.9. Importantly, 64.5% of patients in the two groups were on no medications at month 36. Choroidal effusion, shallow anterior chamber, and persistent hypotony were the most common complications, occurring in 2.9%, 2.5%, and 2.5%, respectively. Because the Xen 45 has “fewer complications with a similar efficacy, we should consider the Xen 45 as the initial choice,” Dr. Varma said.
Allergan is developing Bimatoprost SR, where “the amount of drug that’s in one of those implants is the equivalent of one drop of bimatoprost,” E. Randall Craven, MD, said during AGS, but that one drop lowers IOP for three to six months with one implant.
The biodegradable implant is placed intracamerally using a prefilled, single-use applicator system. Following washout and assessments at baseline (Day –3 to –1), on treatment Day 1, Bimatoprost SR (6-, 10-, 15-, or 20-µg Generation 2 formulation) was administered intracamerally in the study eye (n=75) and the fellow eye began topical bimatoprost 0.03% QD in a Phase I/II prospective, 24-month, dose-ranging, paired eye comparison study. Study eyes that met retreatment criteria were allowed to receive a second administration of Bimatoprost SR after a minimum 90 days and at most 12 months after the first administration.
After delivery, the implant settles on the lower angle, Dr. Craven said. “At 12 months, there’s a bit of the implant still in the bottom of the eye, but by 2 years it’s completely gone. The drug has been depleted before the implant dissolves.” Over 16 weeks, the implant reduced IOP 7.2 to 9.5 mmHg from baseline, comparable to what topical bimatoprost can deliver.
This has the potential to provide “an expanded treatment option for a delivery platform” that’s as good as the topical treatment but with far fewer side effects.