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Jonathan Pieter Vande Geest, Hirut G Kollech, Reza Behkam, Anirban Jana, Urs Utzinger, Christopher A Girkin; Biomechanical Response of the Lamina Cribrosa in Glaucomatous and Non glaucomatous samples. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6189. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma is the second leading cause of blindness in the world. Some of the risk factors for this disease include age, race, gender and intraocular pressure (IOP). More recent studies showed that the biomechanics of the optic nerve head region (ONH) is a critical component for the development of glaucoma. The purpose of this study is to compare the strain response of glaucomatous and non-glaucomatous human eyes in the lamina cribrosa (LC), which a collagenous structure in the ONH.
We used six glaucomatous and five non glaucomatous (NG) eyes from the European descent that were above 50 years old. We conducted a pressure inflation experiment while simultaneously collecting images at 5,15,30 and 45mmHg using multiphoton microscope and calculated the displacement field using Digital Volume Correlation (DVC). DVC results were used to calculate the Green strain components. LC regions were subdivided into four quadrants (inferior, superior, nasal, temporal) and two rings (central, peripheral) to investigate strain regional variations. Statistical analysis was done using Linear mixed model with disease and LC regions as fixed effects and human and eyeballs as random effects.
Our results show regional variation in shear and frontal (in-plane) strain between the glaucomatous and NG samples. A figure showing these differences in the second pressure set (15-30mmHg) is attached below. The xy strain in NG was significantly lower than that of the glaucomatous in all quadrants and rings (Fig 1 A, D and E). On the other hand, the strain in yz of the central rings and nasal quadrant of NG was significantly bigger than that of G (Fig1 B, C and F).
The shear strain in the sagittal plane (Eyz) of glaucomatous samples was lower than NG samples. Most quadrants and rings showed higher shear strain in the frontal plane (Exy) in the glaucomatous group. Our recent work for LC strain differences in racioethnic groups showed similar strain results in the at-risked groups (African and Hispanic groups). This may be due to LC biomechanical similarities present in these groups and glaucoma patients. In future work, we plan on getting axon counts for each sample to get additional information of the ONH region. We will also determine LC material properties of both glaucomatous and non-glaucomatous samples.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Figure 1) Comparison of Green strain metric between glaucomatous and non glaucomatous samples
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