Lamina cribrosa thickness and spatial relationships between intraocular space and cerebrospinal fluid space in highly myopic eyes.

PURPOSE To evaluate the spatial relationships of the intraocular space, the cerebrospinal fluid space, and the lamina cribrosa in highly myopic eyes. METHODS The study included 36 human globes with an axial length of more than 26.5 mm that showed marked glaucomatous optic nerve damage (n = 29; highly myopic glaucomatous group) or in which the optic nerve was affected by neither glaucoma nor any other disease (n = 7; highly myopic normal group). Two non-highly myopic control groups included 53 globes enucleated because of malignant choroidal melanoma (n = 42; non-highly myopic normal group) or because of painful absolute secondary angle-closure glaucoma (n = 11; non-highly myopic glaucomatous group). Anterior-posterior histologic sections through the pupil and the optic disc were morphometrically evaluated. RESULTS In both highly myopic groups compared with both non-highly myopic groups and in the highly myopic glaucomatous group compared with the highly myopic normal group, the lamina cribrosa was significantly (P < 0.001) thinner. Correspondingly, the distance between the intraocular space and the cerebrospinal fluid space was significantly (P < 0.05) shorter in the highly myopic normal group than in the non-highly myopic normal group and in the highly myopic glaucomatous group than in the highly myopic normal group. CONCLUSIONS In highly myopic eyes, the lamina cribrosa is significantly thinner than in non-highly myopic eyes, which decreases the distance between the intraocular space and the cerebrospinal fluid space and steepens the translaminar pressure gradient at a given intraocular pressure, which may explain the increased susceptibility to glaucoma in highly myopic eyes. As in non-highly myopic eyes, thinning of the lamina cribrosa gets more pronounced in highly myopic eyes if glaucoma is also present.