Purpose
To evaluate the characteristics of lamina cribrosa (LC) pores in eyes with primary open-angle glaucoma (POAG) using swept-source optical coherence tomography (SS-OCT).
Methods
Patients with POAG (n=30 eyes) and age-matched healthy individuals (n=10 eyes) were recruited. Optic disc scans were performed by SS-OCT, and 3 mm×3 mm×2.6 mm (512×256×963 pixel) data cube were acquired. Each data volume was reconstructed as C-scan slices by built-in en-face viewer (EnView, DRI OCT-1, Topcon Medical Systems, Oakland, NJ). For each C-scan slices, the automated segmentation procedure, including local contrast enhancement and local thresholding, were performed by Matlab R2014a (The MathWorks, Inc., Natick, MA). LC parameters including pore count, pore diameter, standard deviation (SD) of pore diameter, pore ovality, pore area, pore volume and beam thickness were automatically measured in four quadrants (superior, inferior, nasal and temporal) and compared between the groups. LC parameters associated with increased mean deviation (MD) of visual field (VF) were investigated using general linear model.
Results
The average MD of VF for the POAG and healthy eyes was -9.30±6.10 dB and 1.21±0.65 dB, respectively. There was no significant difference in pore count, pore diameter, SD of pore diameter, and pore volume between the two groups (P>0.05). The pore area was significantly lower in temporal area (641.8±185.8 μm2, P=0.01) and marginally larger in superior area (862.3±206.5 μm2, P=0.052) in POAG eyes compared to healthy eyes (703.3±248.0 and 821.7±166.3 μm2, respectively). The pore ovality was significantly larger at all quadrants in POAG eyes (mean, 1.71±0.16) than in healthy eyes (mean, 1.55±0.19, P=0.009). The beam thickness tended to be lower in POAG eyes, while only superior quadrant showed statistical significance (POAG, 416.3±39.5 μm vs. Healthy, 449.1±55.2 μm, P=0.047). In the multivariate analysis, the pore ovality was significantly associated with decreased MD of VF (beta=-15.161, P=0.006).
Conclusions
Quantitative evaluation of LC pores using SS-OCT demonstrated regional pore area variability and increased pore ovality in POAG eyes. The pore ovality revealed linear relationship with glaucoma severity. Assessment of LC pores may provide structure-function related information in glaucoma patients.