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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Su Guvenir (Erasmus Medical Center)
Stephen A. Schwaner (Georgia Institute of Technology)
Amir A. Zadpoor (TU Delft)
C. Ross Ethier (Georgia Institute of Technology)

Abstract:
Gradual vision loss in glaucoma is caused by the death of retinal ganglion cells (RGCs) primarily in the optic nerve head (ONH). Elevated intraocular pressure (IOP) is a well-known risk factor. Rats are widely used to better understand the biomechanics-driven cell processes between the IOP and the RGC apoptosis. The effect of early stage remodeling is important to understand, and glaucomatous rat eye ONH biomechanics has never been characterized. This research [1], for the first time, characterizes glaucomatous rat eye ONH biomechanics by using individual-specific finite element (FE) modelling. Tissue delineation marks from three-dimensional (3-D) histomorphometric reconstructions [2] were used to build two individual-specific glaucomatous rat ONH FE models (FEMs), which were embedded into a generic posterior eye model. Since the IOP during tissue fixation was reported to be 10 mmHg, FEMs were solved for the IOP change from 10 to 30 mmHg [3]. Moreover, as an upper IOP boundary, experimentally measured IOP values of 32.5 mmHg and 34.6 mmHg [2] were also applied to solve FEMs. As the IOP cause deformations, the mean and the 95th percentile of the 1st (maximum tension) and the mean and the 5th percentile of the 3rd (maximum compression) principal strains on the anterior ON were calculated. The mean of the 1st principal strain ranged from 4.90% to 5.30% and the 95th percentile was 9.48% for both eyes. The mean and the 5th percentile of the 3rd principal strain magnitudes ranged from -4.74% to -4.76% and -7.52% to -8.86%, respectively. Larger strains were located at the inferior side of the anterior ON and strain magnitudes were higher compared to healthy rat ONH FEMs [3]. Relative differences in strains between the healthy and glaucomatous eyes increased when experimentally measured IOP values were applied. To conclude, this research is the first to characterize glaucomatous rat eye ONH biomechanics and suggests that alterations in the ONH geometry due to remodeling and damage in early stages of glaucoma caused higher deformation and larger strains on the inferior side of the anterior ON. These models will also be favorable to better interpret results obtained from rat experimental studies.