MIGS and MICS

Sustained IOP reductions achieved with trabecular bypass stent 
and micro-incision cataract surgery

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Photo of Roibeard O’hEineachain

The iStent® (Glaukos) trabecular bypass implant can reduce intraocular pressure (IOP) in glaucoma patients for periods now reaching up to nine years and can also reduce the need for IOP-lowering medication over the long-term, according to the results of a study presented by Tobias Neuhann MD. “In our series, through five years after implantation during cataract surgery, the iStent showed long-term, stable reduction in IOP and medications, with no intraoperative or postoperative complications typically seen with conventional glaucoma surgeries,” said Dr Neuhann, Marienplatz Eye Clinic, Munich, Germany. The study involved 65 eyes of 43 patients with cataracts and glaucoma or ocular hypertension who underwent a combined micro-incision cataract surgery (MICS) and iStent implantation procedure. It showed that, among those with five years of follow-up, mean IOP was reduced by 37% from preoperative medicated values and the number medications patients needed was reduced by 78%. In addition, all eyes achieved a best corrected visual acuity of 20/40 or better, and 79% achieved 20/25 or better. The patients in the study had a mean age of 72.7 years and were evenly divided with regard to gender. Preoperatively, they had a mean IOP of 23.7mmHg and were receiving a mean of 2.0 glaucoma medications. All patients had cataracts requiring treatment. Their glaucomatous conditions included primary open-angle glaucoma (POAG) in 40 eyes, pseudoexfoliation in 14 eyes, ocular hypertension in 10 eyes, and post-traumatic glaucoma in one eye, Dr Neuhann said. Previous procedures included laser peripheral iridotomy in four eyes, selective laser trabeculoplasty in six eyes and argon laser trabeculoplasty in eight eyes, and trabeculectomy in eight eyes. In all eyes, Dr Neuhann performed MICS using a temporal clear corneal incision and implanted a single iStent through the same incision. The length of follow-up was 48 months in 41 eyes and 60 months in 34 eyes. FIVE-YEAR IOP REDUCTIONS Throughout five years of follow-up, mean IOP remained at 16mmHg or below. Furthermore, IOP was 15mmHg or below in 65%, and 18mmHg or below in 92%. By comparison, preoperative medicated IOP was only 15mmHg or below in only 2%, and 18mmHg or below in only 14%, Dr Neuhann said. In addition, the mean number of IOP-lowering medications patients required fell from 2.0 at baseline to 0.1 at three months postoperative and 0.5 at five years. Furthermore, 69% of those with five years of follow-up remained medication-free. Of the remaining patients, 27% were receiving one to two medications and 4% were receiving three to four medications. Preoperatively, 97% of eyes were receiving at least one medication and 28% were receiving three to four medications, he noted. “When you look for the cost of the medication and the freedom the patient has from the drops, it's not so bad to have 70% of patients medication free after five years. We even have some patients who were implanted nine years ago and are still without medication,” Dr Neuhann added. There were, however, eight eyes that required further surgical interventions. They included one POAG patient and one pseudoexfoliative glaucoma patient who were intolerant of topical and systemic medications and underwent shunt surgery at three months. There were also three patients who underwent cyclophotocoagulation at 12 months, including one who also underwent trabeculectomy at 24 months. Two eyes received a XEN® (AqueSys) ab interno fistularising implant, one eye at 24 months and the other at 48 months. TINY IMPLANT Dr Neuhann noted that the iStent devices are designed to bypass the trabeculum and allow drainage of aqueous from the anterior chamber directly into Schlemm’s canal. They are the smallest medical devices ever to have been implanted in the human body. The original snorkel design used in the study has a length of 1.0mm, a height of 0.33mm and weight of 60 micrograms. It is made of surgical grade heparin-coated titanium. “It is quite small, but it really works. More than 200,000 have been implanted worldwide and it has a clinical history of 10 years,” Dr Neuhann said. He added that the technique for implanting the iStent is very easy to learn for those experienced in using a surgical microscope. It involves the placement of a gonioprism on the cornea to visualise the trabecular meshwork and the iridocorneal angle. The iStent applicator slips the long arm of the device into Schlemm’s canal very easily in most cases. Blood coming from the device’s opening into the anterior chamber indicates a successful implantation. The device is also designed in such a way as to keep the snorkel’s opening safely clear of the iris. “Implantation of a single iStent plus MICS is a sustained, safe and effective treatment for POAG, pseudoexfoliative glaucoma and ocular hypertension,” Dr Neuhann added. Tobias Neuhann: tneuhann@web.de
Tags: glaucomak, mics, migs