Fig 4. Schematic explanation of the method for measuring the elongation index (EI) for the lamina pores in the lamina cribrosa (LC).

(A) En face image and line scan (red arrow). (B) The reflectivity of the lamina pore is tabulated using the Image J program. The boundary of the lamina pore (red arrow) was defined as the point where its reflectivity is lower than the mean lamina beam reflectivity (blue dot line). (C) En face image (left) and magnified view (right). Red dot square corresponds to a magnified view. The red dot line is the fovea-disc line and blue dot line divides each region. (D) Representative pore analysis. In this case, the longest diameter is 20.4 pixels (a) and the shortest diameter is 9.3 pixels (b) for one pore (red arrows), which means that the EI is 2.19. For another pore, the longest diameter is 22.2 pixels (c) and the shortest diameter is 7.5 pixels (red arrows) (d), which means that the EI is 2.96.