Purchase this article with an account.
Thao D Nguyen, Dan Midgett, Baiyun Liu, Harry A Quigley; Analysis for the effects of glaucoma and optic nerve damage on the pressure-induced strains in the human lamina cribrosa. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6190. doi: https://doi.org/.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To estimate the strains in the human lamina cribrosa (LC) in ex vivoinflation tests and analyze for the effects of glaucoma diagnosis and severity of optic nerve axon damage.
Sixteen eyes from 10 diagnosed glaucoma donors and 10 eyes from 8 donors with no history of glaucoma were inflation tested ≤48 hours post mortem. Normal and glaucoma eyes had the same age range (76-93 years)and average age did not differ significantly (83.8 ± 6.1 normals, 87.3 ± 5.4 glaucoma,p=0.12). The axial length was measured using calipers. Myelinated optic nerve was removed from each eye, embedded and sectioned forsemi-quantitative grading of axon lossby a glaucoma expert (HQ) masked todiagnosis. The remaining optic nerve was removed, exposingthe posteriorLCsurface, and the anterior eye structures removedto affixthe posterior sclera and LCin a custommountfor controlled inflationby a manometer.LC wasimaged bya laser-scanning microscopeusingsecond harmonic generation (SHG) imaging at 5, 10 and 45 mm Hg. The SHG image volumes were analyzed using digital volume correlation (DVC) to calculate the three-dimensional displacements and LCstrains. Analysis of variance was applied to compare the strains betweennormal and glaucoma eyes,and among3 damage groups:normal undamaged (<10% axon loss,n=8), glaucoma undamagedormild (<25%,n=9)axon loss, and glaucoma moderate-severe (25%-75%, n=6)axon loss.
The maximum principal strain (Emax), radial strain (Err), circumferential strain (Eθθ), and nasal-temporal strain (EXX) were significantly lower in all diagnosed glaucoma eyes than normal eyes (p < 0.05)at 10 mmHg.Eθθwas lower in diagnosed glaucomathan in normaleyes at 45 mmHg (p = 0.03). In the analysis accounting for axon loss, EXXwas higher in the LC of normal undamaged eyes than in glaucoma undamaged/mild eyes (p = 0.02 at 10 mmHg, p = 0.045 at 45 mmHg). However, LC strains did not differ significantly between normal undamaged and glaucoma moderate/severe damage eyes. Variations in age and axial length did not contribute to the decrease in LC strain, while increasing LC area had the opposite effect on LC strain than in a prior study for normal eyes.
The pressure-strain response of the LC was stiffer in normal vs. glaucoma eyes and in glaucoma undamaged/mild damage eyes vs. normal undamaged eyes. Variations in LC strain response may contribute to glaucoma susceptibility and damage
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
This PDF is available to Subscribers Only