Comparison of 1-Year Effectiveness of Trabecular Microbypass Stent implantation (iStent) in Conjunction With Phacoemulsification Among Mild, Moderate, and Severe Primary Open-angle Glaucoma Patients.

PRECIS: The study compared 1-year effectiveness of single trabecular microbypass stent (iStent) implantation with phacoemulsification among glaucoma severities in primary open-angle glaucoma. The study found that mild glaucoma had greater success rate and lower number of medications compared with moderate and severe glaucoma. PURPOSE: To evaluate the effectiveness of iStent implantation in combination with cataract surgery in moderate to severe glaucoma compared with mild glaucoma. METHODS: Medical charts of primary open-angle glaucoma subjects undergoing 1 iStent implantation were retrospectively reviewed. Glaucoma was classified on the basis of mean deviation (MD) of the preoperative standard automated perimetry into mild (MD>-6 dB), moderate (MD -6 to -12 dB), and severe (MD<-12 dB). Mixed effect regression models were performed to determine the effect of iStent at 1 year. The outcomes included as follows: (1) intraocular pressure (IOP) and the number of medications, (2) eyes with IOP ≤ severity-based target (18 mm Hg for mild, 15 mm Hg for moderate, 12 mm Hg for severe) (2A) without medication, and (2B) with medication reduction. RESULTS: In total, 104 eyes from 89 subjects were analyzed. Cataract combined with iStent surgery significantly lowered the number of medications in all groups and significantly decreased IOP in moderate and severe glaucoma (P<0.05). There was significantly higher number of medications in moderate (β: 0.58, P=0.002) and severe (β: 1.20, P<0.001) compared with mild glaucoma. Eyes with moderate glaucoma had significantly lower rate of success (criterion 2A) compared with mild glaucoma [odds ratio (OR): 0.008, P=0.047]. Eyes with moderate and severe glaucoma had significantly lower rates of success (criterion 2B) (moderate vs. mild OR: 0.002, P=0.028; severe vs. mild OR: 0.026, P=0.026). CONCLUSIONS: Combined phacoemulsification with iStent seems to have a better IOP-lowering and medication-lowering effect in mild glaucoma cases versus those with moderate and severe glaucoma. This difference was found in real-world data over one-year follow-up period. Long-term studies with defined IOP goals and medication removal protocols are warranted.