Comparing the trabecular outflow by the response to topical pilocarpine in patients with and without glaucoma filtering surgery

Purpose: To compare the trabecular outflow by the response to topical pilocarpine administration in patients with and without prior glaucoma filtering surgery.

Study design: Prospective, cross-sectional, randomized, double-blinded study.

Methods: Open-angle glaucoma (OAG) patients without any prior glaucoma surgery, and those with prior trabeculectomy or tube shunt surgery aged 18-90 years were included. Both groups were randomized into pilocarpine or artificial tears (ATs). Intraocular pressure (IOP) was measured before and 90 min after the instillation of eye drops.

Results: A total of 189 eyes of 189 patients were included: 92 eyes in the pilocarpine and 97 eyes in the ATs group. There was a mean ± standard deviation of - 0.81 ± 3.08 mmHg decrease in IOP with pilocarpine in those without prior surgery, significantly higher than the ATs group (0.55 ± 2.31 mmHg; p = 0.02). No significant change in IOP with pilocarpine was noted in the surgical group compared to the ATs group (p = 0.90). In the surgery group, greater IOP reduction was observed with pilocarpine in those who had undergone surgery within the last three years than those who had surgery three or more years prior (- 1.56 ± 2.64 versus 1.41 ± 2.77 mmHg; p = 0.001).

Conclusion: Less IOP reduction was observed with pilocarpine in patients who had filtering surgery more than three years previously compared to those with more recent surgery.