Manchester iStent study: long-term 7-year outcomes

To determine the efficacy and safety of combined phacoemulsification and single first-generation iStent implantation over 84 months.

Single-surgeon, single-centre, uncontrolled prospective interventional study in real-world settings. Forty-one patients with open-angle glaucoma on at least one antihypertensive drop underwent phaco-iStent surgery. This cohort was monitored over the subsequent 84 months. The primary outcome measure was intraocular pressure (IOP). Secondary outcome measures were number of glaucoma drops, visual acuity, cup-disc-ratio (CDR), mean deviation (MD) and visual field index (VFI). Thirty-one (76%) patients survived to 48 months and 19 (46%) patients to 84 months.

At 84 months, we demonstrate an absolute mean reduction of 4.87 mmHg (95% CI 1.62-7.64) for IOP and 0.59 (95% CI 0.03-1.16) for number of glaucoma drops. At the final clinic visit, LogMAR VA improved by 0.21 (95% CI 0.08-0.34), with no significant change in CDR, MD and VFI. Attrition was mainly due to death (27%) and further glaucoma surgery (12%). A single patient suffered from postoperative hyphaema, with no sequalae. Patients at high risk for progression to filtration surgery were defined as those on oral acetazolamide for IOP control, or those fulfilling all the following criteria: IOP ≥ 20 mmHg, CDR ≥ 0.7, MD ≤ -4.0 dB, number of drops ≥ 2. This group is to be considered for surgery as the next step in management according to NICE glaucoma guidelines. These patients (n = 14) demonstrated a more marked final IOP reduction of 6.85 mmHg (95% CI 3.97-9.75) vs 1.62 mmHg (95% CI 0.04-3.22) in their low-risk counterparts (n = 27). Reduction in glaucoma drops was 0.86 (95% CI 0.07-1.64) for the high-risk and 0.56 (95% CI 0.06-1.05) for the low-risk cohort. Further glaucoma surgery was required for 4 (29%) high-risk and 1 (0.5%) low-risk patients over the study period.

Our results strongly suggest that the expected outcome of phaco-iStent surgery is a maintained reduction in intraocular pressure and number of glaucoma medications over 7 years. This is combined with a negligible rate of complications, a sustained improvement in central visual acuity, and a reliable maintenance of peripheral visual function.