Purpose
To compare the measuring methods for the anterior lamina cribrosa surface (ALCS) depths in healthy and glaucomatous eyes using enhanced depth imaging (EDI) spectral domain-optical coherence tomography (SD-OCT).
Methods
A total of seventy eyes from 30 normal subjects and 40 glaucoma patients were enrolled. Serial horizontal B-scans of the optic nerve head were obtained using EDI SD-OCT. ALCS depths (perpendicular distance from the Bruch’s membrane opening plane to the ALCS) were measured at 3 B-scans from 3 locations (superior-midperiphery, mid-horizontal, and inferior-midperiphery) in each eye by two methods. In Method A, the ALCS depth in each B-scan was defined as the average of the 3 measurements from 3 points (the maximum depth point and two additional points, temporally 100 μm, 200 μm apart from the maximum depth point). In Method B, a smooth contour line was drawn following the ALCS and the maximum depth was considered as the ALCS depth in each B-scan. Intraclass correlation coefficient (ICC) was calculated to determine the interobserver agreement of each method. Bland-Altman Plot was performed to determine the agreement of the ACLC values measured by Method A and B. A regression analysis was performed to identify the relationship between clinical parameters and the ALCS depth measured by Method A and B.
Results
The interobserver ICCs for Method A and B were 0.964-0.980 and 0.976-0.988, respectively. Bland-Altman plot showed a tendency that ALCS depth measured by Method B is increasingly greater than that measured by Method A in eyes with larger ALCS depth. ALCS depths measured by Method A and B were significantly larger in glaucomatous eyes than in healthy eyes (567.76 ± 140.48 vs. 411.53 ± 89.51, P < 0.0001 and 590.04 ± 146.83 vs. 416.73 ± 99.35, P < 0.0001, respectively). A higher baseline IOP was significantly correlated with ALCS depth measured by both Method A (partial correlation coefficient = 0.640, P = 0.001) and by method B (partial correlation coefficient = 0.619, P = 0.001).
Conclusions
This study compared the two different measuring methods of ALCS depth. Both methods had low measurement variability and showed the difference between the healthy subjects and glaucoma patients. ALCS depths measured by both methods were correlated with baseline IOP in glaucoma patients.
Keywords: 577 lamina cribrosa •
550 imaging/image analysis: clinical •
495 depth