Racioethnic Differences in the Biomechanical Environment of the Lamina Cribrosa

Abstract

Purpose : It is well established that those of African descent (AD) and Hispanic ethnicity (HE) are disproportionately affected by primary open-angle glaucoma compared to those of European descent (ED). Studies involving the biomechanical environment of the optic nerve head point to the lamina cribrosa (LC) as the primary region of mechanical insult. Investigating the biomechanical factors in the LC among different groups may help elucidate the mechanism for unbalanced outcomes of glaucoma. We investigated quantitative differences in 3D micro-strains within the LC among the three populations.

Methods : We acquired nine pairs of normal human donor poles, three each from AD, HE, and ED (self-identified racioethnicities). The LC was imaged using multiphoton microscopy at four pressure levels: 5, 15, 30, and 45 mmHg. Image stacks of second harmonic generation were collected to a depth of 350 μm. 3D displacement fields were obtained between adjacent pressure pairs for each population, using an automated digital volume correlation technique, which aims to minimize the difference between two 3D datasets by applying a displacement field to one dataset and measuring how closely it matches the other. Three strain invariants were calculated from Green’s strain tensor obtained from the displacement field.

Results : Fig. 1 shows the mean strain invariant values for each population for each adjacent pressure pair. A Student’s t-test between each individual population shows a statistically significant difference for all three LC strain invariants (Table 1).

Conclusions : Experimental results show that the pressure-dependent biomechanical response of the LC is different among the three populations (AD, HE, ED). These quantitative differences should be further verified with larger sample sizes.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Fig. 1: Mean and standard deviation of the pressure-dependent strain invariant values for each population.