In vivo three-dimensional lamina cribrosa strains in healthy, ocular hypertensive, and glaucoma eyes following acute intraocular pressure elevation

PURPOSE. To compare in vivo lamina cribrosa (LC) strains (deformations) following acute IOP elevation in healthy, glaucoma, and ocular hypertensive subjects. METHODS. There were 20 healthy, 20 high-tension primary open-angle glaucoma (POAG), 16 primary angle-closure glaucoma (PACG), and 20 ocular hypertensive (OHT; with normal visual fields) eyes studied. For each test eye, the optic nerve head was imaged three times (at baseline IOP, following an acute elevation of IOP to approximately 35 then 45 mm Hg using an ophthalmodynamomter) using optical coherence tomography (OCT). A three-dimensional (3D) strain-mapping algorithm was applied to both sets of baseline and IOP-elevated OCT volumes to extract IOP-induced 3D strains. Octant-wise LC strains were also extracted to study the pattern of local deformation. RESULTS. The average LC strain in OHT subjects (3.96%) was significantly lower than that measured in healthy subjects (6.81%; P < 0.05). On average, POAG subjects experienced higher strain than the PACG subjects (4.05%), healthy subjects experienced higher strains than the POAG and PACG subjects, but these difference were not statistically significant. Local LC deformations showed lowest strain in the infero-temporal and temporal octant in the POAG and OHT subjects. CONCLUSIONS. We demonstrate measurable LC strains in vivo in humans as a response to acute IOP elevation. In this population, our data suggest that OHT LCs experience lower IOPinduced strains than healthy LCs.