Comparison of the Biomechanics of the Mouse Astrocytic Lamina Cribrosa Between Glaucoma and Optic Nerve Crush Models.

Abstract

The strain response of the mouse astrocytic lamina (AL) to an ex vivo mechanical test was compared between two protocols: eyes that underwent sustained intraocular pressure (IOP) increase and eyes after optic nerve crush. Chronic IOP elevation was induced by microbead injection or the optic nerve was crushed in mice with widespread green fluorescence. After 3 days or 6 weeks, eyes were inflation tested by a published method of two-photon fluorescence to image the AL. Digital volume correlation was used to calculate strains. Optic nerve axon damage was also evaluated. In the central AL but not the peripheral AL, four strains were greater in eyes at the 3-day glaucoma time point than control (P from 0.029 to 0.049, n = 8 eyes per group). Also, at this time point, five strains were greater in the central AL compared to the peripheral AL (P from 0.041 to 0.00003). At the 6-week glaucoma time point, the strains averaged across the specimen, in the central AL, and the peripheral AL were indistinguishable from the respective controls. Strains were not significantly different between controls and eyes 3 days or 6 weeks after crush (n = 8 and 16). We found alterations in the ex vivo mechanical behavior in eyes from mice with experimental glaucoma but not in those with crushed optic nerves. The results of this study demonstrate that significant axon injury does not directly affect mechanical behavior of the astrocytic lamina.