Comparing acute IOP-induced lamina cribrosa deformations pre-mortem and post-mortem

Wei, J.; Hua, Y.; Yang, B.; Wang, B.; Schmitt, S. E.; Lucy, K. A.; Ishikawa, H.; Schuman, J. S.; Smith, M. A.; Wollstein, G.; Sigal, I. A.

doi:10.1101/2022.09.18.508448

bioRxiv · 10.1101/2022.09.18.508448

Comparing acute IOP-induced lamina cribrosa deformations pre-mortem and post-mortem

Wei, J.·Hua, Y.·Yang, B.·Wang, B.·Schmitt, S. E.·Lucy, K. A.·Ishikawa, H.·Schuman, J. S.·Smith, M. A.·Wollstein, G.·Sigal, I. A.

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Abstract

PurposeLamina cribrosa (LC) deformations caused by elevated intraocular pressure (IOP) are believed to contribute to glaucomatous neuropathy and have therefore been extensively studied, in many conditions from in-vivo to ex-vivo. We compare acute IOP-induced global and local LC deformations immediately before (pre-mortem) and after (post-mortem) sacrifice by exsanguination. MethodsThe optic nerve heads of three healthy monkeys 12-15 years old were imaged with spectral-domain optical coherence tomography under controlled IOP pre-mortem and post-mortem. Volume scans were acquired at baseline IOP (8-10 mmHg) and at 15, 30, and 40 mmHg IOP. A digital volume correlation technique was used to determine the IOP-induced 3D LC deformations (strains) in regions visible pre-mortem and post-mortem. ResultsBoth conditions exhibited similar nonlinear relationships between IOP increases and LC deformations. Median effective and shear strains were, on average over all eyes and pressures, smaller post-mortem than pre-mortem, by 14% and 11%, respectively (Ps < 0.001). Locally, however, the differences in LC deformation between conditions were variable. Some regions were subjected pre-mortem to triple the strains observed post-mortem, and others suffered smaller deformations pre-mortem than post-mortem. ConclusionsIncreasing IOP acutely caused nonlinear LC deformations with an overall smaller effect post-mortem than pre-mortem. Locally, deformations pre-mortem and post-mortem were sometimes substantially different. We suggest that the differences may be due to weakened mechanical support from the unpressurized central retinal vessels post-mortem. Translational RelevanceAdditional to the important pre-mortem information, comparison with post-mortem provides a unique context essential to understand the translational relevance of all post-mortem biomechanics literature. PrecisThe authors compared in monkeys acute IOP-induced deformations of the lamina cribrosa pre-mortem and post-mortem. Deformation trends were similar pre-mortem and post-mortem, but deformations pre-mortem were generally smaller than those post-mortem, with substantial local variations. The differences are likely due to loss of vessel support post-mortem.

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Wei, J., Hua, Y., Yang, B., Wang, B., Schmitt, S. E., Lucy, K. A., Ishikawa, H., Schuman, J. S., Smith, M. A., Wollstein, G., Sigal, I. A.. 2022-09-19. Comparing acute IOP-induced lamina cribrosa deformations pre-mortem and post-mortem. https://doi.org/10.1101/2022.09.18.508448

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