Abstract
Purpose :
To measure the ex-vivo pressure-induced strain response, curvature, and features of the collagen beam-network structure of the human lamina cribrosa (LC) and analyze for differences between diagnosed glaucoma and age-matched normal eyes.
Methods :
We received 10 normal eyes and 15 diagnosed glaucoma eyes with axon loss ranging from <25% to >75% with an age range of 76-93 years and average ages 83.8 ± 6.1 years and 87 ± 5.3 years respectively. The posterior scleral cup specimens were subjected to inflation testing and second harmonic generation (SHG) imaging (Midgett et al. 2017). SHG image volumes were analyzed using digital volume correlation (DVC) to calculate the strain field caused by inflation from 5-45 mmHg (Fig 1b). The SHG images were enhanced using deconvolution and Frangi’s filter (Campbell et al. 2015), then analyzed by a custom algorithm (Ling et al. 2019) to measure 10 features of the LC collagen beam-pore network (Fig 1c). Curvatures of the LC were determined by fitting a 5th order polynomial to the surface of the DVC correlated LC volume (Fig 1d). The structural and strain outcomes were averaged for each specimen and unpaired t-tests were used to compare structural features and curvature.
Results :
Axial length, LC area, and mean curvature were larger in eyes diagnosed with glaucoma compared to normals (p≤ 0.03) (Fig 2). The circumferential strain was lower in glaucoma eyes (p = 0.03). LC network structure did not statistically differ between normal and glaucoma eyes.
Conclusions :
While diagnosed glaucoma eyes had greater LC curvature, area, and axial length, each of which should result in a larger strain response, their strains were smaller than normal LC. The lack of association between LC network structure and strain response suggest that there are different material properties that explain the lower strains.
This is a 2020 ARVO Annual Meeting abstract.