COMPARISON OF SCHLEMM’S CANAL PARAMETERS IN PSEUDOEXFOLIATIVE GLAUCOMA AND PRIMARY OPEN-ANGLE GLAUCOMA: A SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY STUDY

The aim of this study is to compare Schlemm’s canal (SC) parameters obtained using swept-source optical coherence tomography (SS-OCT) in eyes with pseudoexfoliative glaucoma (PXG) and primary open-angle glaucoma (POAG), and to investigate the associations between these parameters and various ocular variables.

Cross-sectional observational study

In this cross-sectional observational study, 30 eyes from 26 patients with PXG and 30 eyes from 27 patients with POAG, all under follow-up at the outpatient clinic of Kartal Dr. Lütfi Kırdar City Hospital, a tertiary referral center, were included. Nasal and temporal Schlemm’s canal images were obtained using an anterior segment OCT device (Triton DRI-OCT, Topcon, Tokyo, Japan). The images were then exported, and the calculation of Schlemm’s canal measurements (Schlemm’s canal length (SCL) and Schlemm’s canal area (SCA) was performed using ImageJ. SC parameters were compared between the two groups, and additionally, the relationships of these parameters with age, intraocular pressure (IOP), cup-to-disc ratio, retinal nerve fiber layer (RNFL) thickness, and the number of antiglaucoma medications (NAGM) used were evaluated within each group.

The mean age of patients was 68 ± 8 years in the PXG group and 65 ± 7 years in the POAG group. In the PXG group, 17 patients were male, while in the POAG group, 15 patients were male. The mean IOP and NAGM were 17 ± 3 mmHg and 3 ± 1 in the PXG group, and 17 ± 2 mmHg and 3 ± 1 in the POAG group, respectively. There was no significant difference between the groups in terms of nasal SCL (p > 0.05), whereas temporal SCL was significantly lower in the PXG group compared to the POAG group (p = 0.038). No significant difference was observed between the groups in SCA (p > 0.05). In the PXG group, no significant associations were found between SC parameters and variables such as age, IOP, cup-to-disc ratio, RNFL thickness, or the NAGM. In the POAG group, however, a moderate negative correlation was observed between temporal SCA and cup-to-disc ratio (r = -0.387, p = 0.035).

In PXG, which is known to have a more aggressive course than POAG, temporal SCL was found to be lower compared to the POAG group. SC plays a key role in IOP regulation, and the lower SCL observed in PXG may be related to anatomical factors or pathophysiological mechanisms contributing to its more aggressive course. The presence of a larger cup-to-disc ratio is known to be associated with more advanced glaucoma. In our study, the negative correlation between cup-to-disc ratio and temporal SCA in the POAG group suggests that eyes with advanced POAG may exhibit regionally reduced SCA. Further studies with larger patient populations are needed for more detailed evaluation.