The change of ciliary muscle-trabecular meshwork-Schlemm canal complex after phacoemulsification using swept-source optical coherence tomography.

Abstract

Introduction: Cataract surgery has been reported to have a reducing effect on intraocular pressure (IOP) in glaucomatous and non-glaucomatous eyes. This effect seems to be more noticeable in eyes with narrow angles (NAs) than in eyes with open angles (OAs). Decrease in IOP may be a result of the increase in anterior chamber angle (ACA) and Schlemm canal (SC) after cataract surgery. The purpose of this paper is to evaluate the relationship between Schlemm canal-cross-sectional area (SC-CSA) changes and trabecular meshwork, ciliary muscle changes after cataract surgery and the difference in non-glaucomatous eyes with narrow angles and open angles.

Methods: Intraocular pressure, SC-CSA, Schlemm canal diameter (SCD), trabecular meshwork width (TMW) and thickness (TMT), trabecular-iris angle at 500 µm from the scleral spur (TIA500), and the distance between the inner apex of the ciliary muscle and scleral spur (IA-SS) were measured by swept-source optical coherence tomography preoperatively and 1-week post-surgery. Patients were divided into NA and OA groups according to the degree of TIA500, and SC-CSA-related parameters were compared.

Results: Seventy-five patients (89 eyes) were included. IOP significantly decreased, SC-CSA, SCD, TMW, TMT, and TIA500 significantly increased post-surgery (P<0.001). Changes in nasal SC-CSA were associated with TMW (P=0.003) and TIA500 (P<0.001) changes; changes in temporal SC-CSA were associated with TMW (P=0.001) and TMT (P<0.001) changes. SC-CSA expansion was correlated with changes in TMW (3.726±1.085, P=0.001 nasally; 3.405±0.945, P=0.001 temporally), TMT (5.224±2.033, P=0.012 nasally; 11.853±3.059, P<0.001 temporally), and TIA500 (40.330±15.100, P=0.009 nasally; 35.453±17.527, P=0.047 temporally). There was no association between SC-CSA expansion and IA-SS changes. SC-CSA expansion was greater in the NAs than in the OAs group (P<0.001).

Conclusion: Cataract surgery results in IOP reduction and SC-CSA expansion. Increased SC-CSA correlates with increases in TMW, TMT, and TIA500. SC-CSA increased more in NAs than in OAs group post-surgery, which may explain the greater decrease in IOP in eyes with NAs.