Microarchitecture of Schlemm Canal Before and After Selective Laser Trabeculoplasty in Enhanced Depth Imaging Optical Coherence Tomography
To characterize the in vivo effect of selective laser trabeculoplasty (SLT) on the Schlemm canal (SC) in eyes with primary open-angle glaucoma (POAG).Materials and Methods:
Eighty-one serial horizontal enhanced depth imaging optical coherence tomograph B-scans (interval between B-scans, ∼35 μm) of the nasal corneoscleral limbus were obtained before and 4 weeks after SLT. Fifty B-scans in the overlapping regions before and after SLT were selected for analysis based on the structures of aqueous and blood vessels as landmarks. The SC cross-sectional area (CSA) was measured in each selected B-scan and averaged to generate the mean SC CSA of the eye. SC volume in the overlapping region was calculated using commercially available 3-dimensional reconstruction software. The mean SC CSA and SC volume were compared between pre-SLT and post-SLT B-scans. Correlation analysis was performed between SC CSA changes and intraocular pressure (IOP) changes.Results:
Thirteen POAG eyes (13 patients) were included for analysis (mean age, 68.2±9.2 y). After SLT, the mean IOP was reduced from 19.8±7.6 to 14.4±3.8 mm Hg (P=0.003); the mean SC CSA increased by 8%, from 2478±550 to 2682±598 μm2 (P=0.029); and the mean SC volume increased from 4,304,592±954,777 to 4,658,250±1,039,956 μm3 (P=0.029). Increase in SC CSA had a significant positive correlation with IOP reduction after SLT (P=0.023, R=0.622).Conclusions:
SLT expands SC in POAG patients and even more so with greater IOP reduction after SLT. Post-SLT expansion of SC may be due to increased trabecular aqueous outflow, IOP decrease, or structural changes in trabecular meshwork resulting from SLT.