Deceptive appearances: Identification of the anterior lamina cribrosa surface

Abstract

Purpose : Lamina cribrosa (LC) is an important target for research as it is considered to be involved in initial glaucomatous damage. Changes in the LC macrostructure have been identified, which rely on accurate outlining of the anterior LC surface (ALCS). However, identifying the accurate location of ALCS in OCT images is not yet determined. The purpose of this study is to compare the outcomes of two different approaches in the demarcation of the ALCS: 1. Using cross-section scans only (xsection method); 2. Combining cross-section and enface scans (combined method).

Methods : Spectral-domain OCT scans (Leica, Chicago, IL) of the optic nerve head (ONH) cube were acquired in vivo from healthy rhesus monkeys. 3D OCT image data were resampled along radial lines at every 15 degrees centered on the geometric center of the optic disc resulting in 12 -cross-sectional images for each volume. Four points of a fixed distance from the center on each cross-sectional image were used to represent ALCS depth (Figure). ALCS was determined in the cross-section scans as the points where a high intensity signal intersected with the high-intensity prelaminar glial columns (xsection method). Then, looking at the corresponding enface image, the detected ALCS was modified when needed (combined method). The modified amount of shift along the anterior-posterior axis was recorded as the difference between the two methods.

Results : 15 eyes from 11 healthy adult Rhesus macaque were analyzed. Combined method consistently found deeper locations as ALCS compared to xsection method (Table 1). Dividing the outcomes to 4 quadrants (Table 2), the superior nasal quadrant showed significantly larger difference than the inferior temporal quadrant (p < 0.05) and the superior temporal quadrant (p <0.001).

Conclusions : The ALCS was consistently identified deeper using the en face scans, compared to the radial cross-sectional scans alone, most notable in the superior nasal quadrant. Considering this discrepancy, it is recommended using the combination of both approaches to accurately detect the ALCS.

This is a 2021 Imaging in the Eye Conference abstract.