Age-related changes in quantitative strain of mouse astrocytic lamina cribrosa and peripapillary sclera using confocal microscopy in an explant model

PURPOSE. The purpose of this study was to measure the full-field deformation response to IOP change in the peripapillary sclera (PPS) and astrocytic lamina cribrosa (ALC) of young and old mouse eyes ex vivo. METHODS. Thirty-eight transgenic reporter mice with green fluorescent protein–expressing astrocytes were studied at 2 to 4 months and 13 to 15 months old. The ALC and PPS of the explant eyes were imaged using laser scanning microscopy under controlled inflation from 10 to 30 mm Hg. Strains were estimated for the ALC and PPS from imaged volumes using digital volume correlation. RESULTS. ALC strains were significantly greater than zero nasal–temporally for both age groups (mean = 4.3% and 4.0%; each P ≤ 0.004) and significantly greater than zero in the inferior– superior direction for younger mice (P = 0.0004). Younger mice had larger ALC inferior– superior strains than older mice (P = 0.002). The ALC area and perimeter enlarged with inflation in both age groups, with a greater increase in younger than in older mice (all P ≤ 0.004). The ALC nasal–temporal diameter change was greater than inferior–superiorly, and younger mice had greater enlargement nasal–temporally than older. PPS maximum shear strain was greater in the older mice (P = 0.002). The axial lengths of older mice were 14% longer and the PPS was 16% thinner than younger mice (both P = 0.0003). CONCLUSIONS. The behavior of the ALC in younger mice with inflation exhibited greater strains and enlargement of ALC area than older mice. Some strain measures in the PPS were greater in older mice, likely related to their longer axial length and thinner PPS.