The long-term effects of the first and second glaucoma drainage implant surgery in patients with primary open-angle glaucoma

Background: To investigate the long-term outcome of non-valved glaucoma drainage implant surgery (GDIS) in primary open-angle glaucoma (POAG) patients divided in Group I (patients who underwent the first GDIS) and Group II (patients who underwent the second GDIS because of the failed first GDIS). Methods Intraocular pressure (IOP), visual acuity (VA), visual field defect (VFD), medication score (MS), survival rate, complications, and patient background was retrospectively analyzed. Two success criteria were set: Criteria 1) IOP reduction ≥ 20% and 5 < IOP ≤ 21, Criteria 2) IOP reduction ≥ 20% and 5 < IOP ≤ 14. Results There were 136 eyes of 109 patients in Group I and 32 eyes of 27 patients in Group II. In Group I and II, mean preoperative IOP was 26.7 ± 6.7 mmHg and 23.7 ± 3.5 mmHg, respectively ( P  = 0.09). No statistically significant difference in postoperative IOP reduction was found between the two groups ( P  = 0.39). At 5-years postoperative, the Criteria 1 (Criteria 2) survival rate in Group I and Group II was 60.4% (31.7%) and 61.2% (25.6%), respectively (Criteria 1: P  = 0.24; Criteria 2: P  = 0.48). No significant difference in VA, VFD change, MS, or complications was observed. Young patient age was the only significant factor for failure in Group Ⅰ ( P  = 0.03). Conclusion The second GDIS may be as effective as the first GDIS for IOP reduction in POAG patients, however, there is a high risk of failure in young-age patients and the surgery may be ineffective in eyes requiring Criteria 2.