Long-term intraocular pressure control for glaucoma patients

“We have found the iStent to be a safe and effective treatment option through four years postoperative in patients with ocular hypertension or open-angle glaucoma,” said Tobias Neuhann MD, Marienplatz Eye Clinic, Munich, Germany.

Dr Neuhann presented a study involving 63 eyes of 41 patients with cataracts and glaucoma or ocular hypertension who underwent a combined micro-incision cataract surgery (MICS) and iStent implantation procedure. It showed that, throughout four years of follow-up, IOP was reduced by 33 per cent from preoperative medicated values, and the number of medications patients needed was reduced by 78 per cent.

Moreover, visual outcomes were good, with 95 per cent achieving a visual acuity of 20/40 or better and 68 per cent achieving 20/25 or better. The procedure also had none of the intra- or postoperative complications typically seen with conventional glaucoma surgeries, Dr Neuhann said.

The patients in the study had a mean age of 72.8 years and were evenly divided with regard to gender. Preoperatively they had a mean IOP of 24.1mmHg and were receiving a mean of 1.9 glaucoma medications, and all but three eyes were receiving at least one IOP-lowering medication, and 37 were receiving two or more.

All patients had cataracts requiring treatment. Their glaucomatous conditions included primary open-angle glaucoma in 39 eyes, pseudoexfoliation in 11 eyes, ocular hypertension in 10 eyes, secondary glaucoma in one eye and post-traumatic glaucoma in one eye.

Previous procedures the patients had undergone included laser peripheral iridotomy in four eyes, selective laser trabeculoplasty in eight eyes and argon laser trabeculoplasty in six eyes, and trabeculectomy in eight eyes.

In all eyes, Dr Neuhann performed MICS using a temporal clear incision and implantation of a single iStent through the same incision. The length of follow-up was 36 months in 41 eyes and 48 months in 34 eyes.

Throughout four years of follow-up, mean IOP remained at 18mmHg or below. In addition, the mean number of IOP-lowering medications fell from 1.9 at baseline to 0.1 at three months postoperative, and at four years remained low at 0.5 medications. Furthermore, 58 per cent were medication free throughout follow-up.

Postoperatively, two patients were intolerant of topical and systemic therapy and underwent shunt surgery. Three patients underwent cyclophotocoagulation.

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.

“Implantation of a single iStent plus MICS is a sustained, safe and effective treatment for primary open-angle glaucoma, pseudoexfoliation and ocular hypertension,” Dr Neuhann added.

Lower IOPs less reduced

The results of another study indicated that, in primary open-angle glaucoma patients with well-controlled IOP, the iStent may reduce the amount of medications needed to achieve that control but will not lower IOP significantly further, said George HH Beiko FRCSC, McMaster University and University of Toronto, Canada.

Dr Beiko retrospectively analysed the efficacy of the iStent in 49 of the first 100 patients to receive the devices at his centre, for whom three-year postoperative data was available. As in Dr Neuhann’s study, the patients all had visually significant cataracts, however their preoperative IOP was better controlled, with a mean value of 16.83mmHg.

The Canadian researchers found that there was no statistically significant change in mean IOP at six months, 12 months, or three years, with respective values of 15.875mmHg, 16.42mmHg, and 16.531mmHg.

However, there was a stable reduction in the number of medications patients required, from 1.6735 preoperatively to 1.0 at six months (p= 0.001) and 12 months (p=0.002), and 0.9184 at three years (p= 0.000).

In addition, the number of patients requiring no topical glaucoma medications rose from two at baseline to 22 at six months, and 28 at three years. Furthermore, the number of patients requiring two or more topical medications fell from 27 at baseline to 19 at three years.

Dr Beiko noted that reduction in the requirements for topical medications has considerable clinical relevance, given that studies have shown that only 56 per cent of patients use more than 75 per cent of the expected doses and only half of glaucoma patients refill their medication within six months of receiving their initial 90-day supply. Nonadherence to prescribed medications results in a greater risk for blindness in glaucoma patients, he added.

Tobias Neuhann: tneuhann@web.de

George HH Beiko: george.beiko@sympatico.ca