Glaucoma is an ocular disease that causes characteristic changes to the optic nerve and visual field. Optical coherence tomography (OCT) is a non-invasive method of objectively quantifying glaucomic structural changes with a high level of reproducibility. It has conventionally been difficult to measure lamina cribrosa, which is the site of axonal damage to the optic nerve head in glaucoma, in eyes. Recent adjustments in OCT and selection of high-depth laser wavelengths has enabled to visualize the anterior surface of the lamina cribrosa, and deformation and defects are frequently observed at this site in glaucoma patients. Meanwhile, because it is difficult to appropriately examine the posterior surface of the lamina cribrosa, measurement of lamina cribrosa thickness had been an unresolved issue. In the present study, we developed a software for such measurements. This software extracted sections that were horizontal and vertical to the lamina cribrosa out of three-dimensional data reconstructed from volume data imaged focusing on the optic disc and measured the posterior surface of the lamina cribrosa as a site at which the pore structure of the lamina cribrosa could be distinguished. Results demonstrated that the lamina cribrosa had already thinned at the pathological stage of preperimetric glaucoma, and lamina cribrosa thickness strongly correlated with the extent of visual field abnormalities and axonal damage. To elucidate that mechanism, we developed simple lamina cribrosa thickness measurement software that could be used to quickly measure lamina cribrosa thickness. Our investigation proved that lamina cribrosa thickness correlates strongly not only with glaucoma severity but also with disc cupping size and optic nerve head tissue blood flow. It is anticipated that objective evaluation of lamina cribrosa thickness with OCT will be applied to processes such as early detection, pathophysiology elucidation, and progress prediction for cases of glaucoma.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 122: 825-831, 2018.