Purpose: To analyze the intraocular pressure (IOP) lowering effect, prognostic factors, and complications that occurred after iStent inject® or XEN® implantation in South Korea. Methods: We retrospectively analyzed 83 eyes with glaucoma who were followed-up for more than 6 months after iStent inject® or XEN® implantation alone or combination with cataract surgery. The success of surgery was defined as an IOP ≤21 mmHg and IOP reduction ≥20% from preoperative IOP. Results: The average IOP drop rate for 6 months after surgery was 33.80% for iStent inject® (group A, 24 eyes), 24.91% for XEN® (group B, 15 eyes), 20.47% for combined iStent inject® and cataract surgery (group A-1, 32 eyes), and 30.39% for combined XEN® and cataract surgery. The cumulative success rate of 6 months after surgery was 45.5% ± 11.2% for group A, 52.8% ± 15.4% for group B, 51.9% ± 9.0% for group A-1, and 83.3% ± 10.8% for group B-1. The difference in success rates between groups A and B was not statistically significant (p = 0.574), and also between groups A-1 and B-1 (p = 0.079). Conclusions iStent inject® and XEN® both have a significant effect on lowering IOP, regardless of combining cataract surgery. XEN® implantation led to a statistically significant reduction in IOP lowering medications.