Purpose: To achieve a highly balanced comparison of trabecular bypass stenting (IS2, iStent inject)with ab interno trabeculectomy (T, Trabectome) by exact matching. In a similar study, IS1 (1st generation iStent) had shown a loss of effect at 6 months.
Methods: 53 IS2 eyes were matched to 3446 T eyes. Patients were matched using exact matching by baseline IOP, the number of glaucoma medications, and glaucoma type and using nearest neighbor matching by age. Individuals without a close match were excluded. All surgeries were combined with phacoemulsification.
Results: A total of 78 eyes (39 in each group) could be matched as exact pairs with a baseline IOP of 18.3+/-5.1 mmHg and glaucoma medications of 2.7+/-1.2 in each. IOP in IS2 was reduced to 14.6+/-4.2 mmHg at 3 months and in T to a minimum of 13.1+/-3.2 mmHg at 1 month. In IS2, IOP began to rise again at 6 months, eventually exceeding baseline. At 24 months, IOP in IS2 was 18.8+/-9.0 mmHg and in T 14.2+/-3.5 mmHg. IS2 had a higher average IOP than T at all postoperative visits (p<0.05 at 1, 12, 18 months). Glaucoma medications decreased to 2.0+/-1.5 in IS2 and to 1.5+/-1.4 in T.
Conclusion: T resulted in a larger and sustained IOP reduction compared to IS2 where a rebound occurred after six months to slightly above preoperative values. This time course fits the bioreactivity data of the IS1.