Changes in Schlemm's canal morphology after trabeculectomy in open angle glaucoma assessed using anterior segment optical coherence tomography.

Clinical relevance: Determining how Schlemm's canal is affected by trabeculectomy may become a marker for evaluating and monitoring surgical success.

Background: This study aims to evaluate the morphological changes in Schlemm's canal after trabeculectomy using anterior segment optical coherence tomography (AS-OCT).

Methods: Thirty-five eyes of 35 patients who were followed up for open-angle glaucoma and indicated for trabeculectomy were included in the study. AS-OCT was performed preoperatively and at week 1, month 1 and month 3 postoperatively. The coronal and meridional diameters of Schlemm's canal were measured in the temporal and nasal quadrants via AS-OCT.

Results: The meridional diameter length of Schlemm's canal was higher in the nasal quadrant than in the temporal quadrant. Nasally, the mean preoperative meridional diameter length was 326.8 ± 88.5 μm, which increased at postoperative week 1 and month 1. Temporally, it was 271.5 ± 91.5 μm and showed a non-significant change postoperatively. The mean preoperative coronal diameter length was 10.9 ± 6.5 μm and 11.9 ± 6.0 μm in the nasal and temporal quadrants, respectively. A statistically significant increase was found in the measurements of the nasal quadrant at week 1 (p = 0.005) and month 1 (p = 0.049), and in the temporal quadrant at week 1 (p = 0.023).

Conclusion: A significant enlargement of the canal occurs at the first postoperative week, followed by a gradual reduction thereafter. The increase in size is mostly observed in the coronal diameters, resulting in the expansion of the canal.