Surgical outcomes of trabecular micro-bypass minimally invasive glaucoma surgery devices in eyes with high myopia: a 24-month retrospective multicenter cohort study

Abstract Background To describe outcomes of two trabecular bypass minimally invasive glaucoma surgery (MIGS) devices in highly myopic (HM) eyes with glaucoma up to 24 months postoperatively. Methods A retrospective, observational multicenter study of HM eyes (phakic refractive spherical equivalent ≤ −6 D and/or axial length ≥ 26 mm) undergoing trabecular bypass MIGS between January 2019 and December 2023. Changes in intraocular pressure (IOP), anti-glaucoma medications and visual acuity, and rates of complications including hyphema, peripheral anterior synechiae and significant IOP elevation, defined as ≥ 30 mmHg or an increase of ≥ 6 mmHg from preoperative IOP, were recorded. IOP outcome criteria and surgical success were reported per European Glaucoma Society and American Academy of Ophthalmology (AAO) guidelines, respectively. Linear mixed models were used for continuous variables, logistic regression for categorical variables and cluster-adjusted Cox regression to compare survival between groups. Results Two hundred and fifty-two eyes of 207 subjects across three centers were studied. One hundred and twenty-eight eyes received iStent inject and 124 received Hydrus microstent; 96.1% of iStent and 100% of Hydrus eyes underwent combined phacoemulsification. At 24 months postoperatively, ≥ 20% IOP reduction with anti-glaucoma medications (AGMs) was achieved by 35.8% (Hydrus) or 30.0% (iStent); or without AGM 13.4% (Hydrus) or 6.67% (iStent). Drop-freedom was achieved by 48.7% (Hydrus) or 38.5% (iStent). An IOP of ≤ 15 mmHg with AGM was achieved by 55.2% (Hydrus) or 63.3% (iStent); or without AGM 28.4% (Hydrus) or 21.7% (iStent). The 12-month cumulative risk of failure to maintain ≥ 20% IOP reduction with AGM was 86.7% (Hydrus) or 90.3% (iStent); or without AGM 90.1% (Hydrus) or 92.5% (iStent). Surgical success based on AAO guidelines was attained by 60.5% (Hydrus) or 53.8% (iStent) of eyes. Significant IOP elevation was the most common complication (4.84% Hydrus; 4.54% iStent), followed by hyphema (0.8% Hydrus; 4.5% iStent) at 1 month postoperatively. Outcomes did not differ significantly between the Hydrus and iStent groups. Conclusions Both iStent inject and Hydrus microstent achieved modest IOP-lowering efficacy and low complication rates in HM eyes. Neither device exceeded the minimal clinically important difference proposed for MIGS combined with cataract surgery.