The additive intraocular pressure (IOP)-lowering effect of goniosynechialysis (GSL) on top of phacoemulsification (PEI) in primary angle-closure (PAC)/PAC glaucoma is controversial. 1-3 Dr. Husain and colleagues are commended for conducting a multicenter randomized clinical trial to compare the efficacy of PEI-GSL versus PEI in 78 eyes with PAC/PACG.3 All eyes had 90° or more of peripheral anterior synechia (PAS). At 12 months follow-up, there were no significant differences between the two groups in mean IOP, change in IOP and number of medication from baseline, and success rate (defined as IOP ≤ 21 mmHg and a decrease in IOP of ≥ 20%).
It is notable that conflicting findings were found in participants from Singapore (N = 30) and Vietnam (N = 30), which the authors attributed to differences in the baseline characteristics between the two study populations. PEI was better than PEI-GSL in the Vietnam group who had a higher baseline IOP, higher proportion of PACG, and shallower anterior chamber depth (ACD) (1.85 ± 0.13 mm versus 2.42 ± 0.30 mm). We have demonstrated that shallower ACD is associated with better IOP control after PEI in PAC/PACG eyes,4 indicating that a large lens with pupillary block mechanism plays a more significant role in eyes with shallower ACD. Regretfully the authors did not consider baseline ACD in their Cox proportional hazards regression model.
Phacoemulsification alone is able to decrease the IOP, reduce the extent of PAS and increase aqueous outflow facility
PEI-GSL may result in a greater reduction in iridotrabecular contact and increase in aqueous outflow facility than PEI,3,5,6 but not necessarily has better IOP-lowering efficacy. These findings could be explained by the fact that PEI alone is able to decrease the IOP, reduce the extent of PAS and increase aqueous outflow facility.7 The restoration of aqueous outflow facility in re-exposed trabecular meshwork following GSL is uncertain. Current evidence suggests that PEI has comparable IOP-lowering effects as PEI-GSL while having the advantages of lower surgical risk and higher cost-effectiveness.