IOP control good with one stent – and better with two or three
Antonio Maria Fea MD
Implantation of the iStent® (Glaukos) trabecular bypass device as a standalone procedure provides significant intraocular pressure (IOP) reduction over the long-term for patients with open-angle glaucoma and the effect is enhanced through the use of multiple stents, said Antonio Maria Fea MD, PhD, Clinica Oculistica, Universita di Torino, Italy.
Dr Fea presented the 30-month follow-up results of an ongoing prospective randomised trial comparing outcomes with one, two, or three of the stents as a standalone treatment for open-angle glaucoma patients, at the XXXIV Congress of the ESCRS in Copenhagen, Denmark.
The study showed that all three treatment groups maintained a mean IOP below 18mmHg throughout the follow-up period. However, the groups implanted with more than one stent lasted for a longer period postoperatively without requiring IOP-lowering medication.
“Both IOP and medication use were reduced through 30 months after implantation of a single trabecular micro-bypass stent as a sole procedure in open-angle glaucoma. Additional IOP reduction to less than 15mmHg has been shown with multiple stents,” Dr Fea said.
The study was carried out by the MIGS study group at the S.V. Malayan Ophthalmological Center in Yerevan, Armenia, where visiting and staff surgeons performed the surgeries. In total, 119 eyes of 119 patients were included in the trial. At the time of Dr Fea’s presentation, 117 had reached 30 months’ follow-up. The MIGS study group will continue monitoring the patients for five years of follow-up.
The patients in the study had a mean age of 67 years and were randomised into three similarly sized groups to undergo implantation of one, two, or three of the original snorkel-shaped iStent devices. One patient in the two-stent group had pseudoexfoliative glaucoma, and the remaining patients had primary open-angle glaucoma.
The mean medicated preoperative IOP was 19.8mmHg in the one-stent group, 20.1mmHg in the two-stent group and 20.4mmHg in the three-stent group. Preoperative post-washout IOP was 25.0mmHg in the one-stent group, 25.0mmHg in the two-stent group and 24.9mmHg in the three-stent group.
At 30 months postoperatively, mean IOP was 15.2mmHg in the one-stent group, 15.0mmHg in the two-stent group and 13.0mmHg in the three-stent group. Furthermore, excluding patients who underwent subsequent cataract surgery, only about 10% of patients in the three groups required IOP-lowering medication during the first postoperative year.
In this present series of patients receiving a single stent or multiple stents as sole therapy, there was a sustained reduction in IOP with a reduction in drug burden in all patients through 30 months
However, by 30 months the proportion requiring medication had risen to about 25% among those with only one stent, but remained unchanged in the other two treatment groups.
The safety profile of the procedures was also favourable, Dr Fea said. There were no intraoperative or perioperative complications. In addition, postoperative best corrected visual acuity (BCVA) was comparable in the three groups and was 20/40 or better in nearly 80% of eyes. There was a postoperative loss of one or more lines of BCVA in four eyes in the one-stent group, three eyes in the two-stent group and four eyes in the three-stent group, although nine of these 11 eyes had BCVA of 20/40 or better.
Dr Fea noted that the findings of his study appear to confirm previous clinical observations that, as standalone procedures, implantation of one iStent achieves long-term, stable IOP control, and use of two or three iStents results in further IOP lowering than that achieved with a single stent.
The enhanced IOP reduction may be due not only to each stent providing additional drainage of the aqueous. It may also result from the increased chance surgeons have of placing a stent in an optimum position in relation to collector channels of Schlemm’s canal, he said.
To optimise the placement of the iStent implants, Dr Fea and his associates have devised a means of localising the collector channels by using a special dye. However, whether this will improve outcomes will not be known until the completion of randomised control trials.
“In this present series of patients receiving a single stent or multiple stents as sole therapy, there was a sustained reduction in IOP with a reduction in drug burden in all patients through 30 months,” he concluded.
Antonio Maria Fea: firstname.lastname@example.org