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Cameron Czerpak, Yik Tung Tracy Ling, Joan L. Jefferys, Harry A Quigley, Thao D. Nguyen; The Curvature and Collagen Network of the Human Lamina Cribrosa in Glaucoma and Control Eyes. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1656.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the curvature and features of the collagen beam-network structure of the lamina cribrosa (LC) of post-mortem human glaucoma eyes and analyze for differences between diagnosed glaucoma and age-matched normal eyes.
The posterior scleral cups of 10 normal eyes and 16 diagnosed glaucoma eyes (Midgett et al. 2020) with axon loss ranging from <10% to >50% were subjected to inflation testing with second harmonic generation (SHG) imaging, and analysis by digital volume correlation (DVC). SHG image Z stacks were analyzed by a custom algorithm (Ling et al. 2019) for ten structural features of the LC beams (Fig 1). The LC curvature was estimated by fitting a 5th order polynomial to the anterior surface of the imaged LC volume (Fig 1d). The structural and strain outcomes were averaged overall and regionally for each specimen. Results will be verified using generalized estimating equation models and linear mixed models.
Preliminary results using unpaired t-tests show mean curvature, Gaussian curvature, and tortuosity averaged over the LC, the central region, and the peripheral region were significantly greater in the LC of diagnosed glaucoma eyes compared to age-matched normal eyes (all p≤0.03) (Fig 2). The specimen-averaged pore size, and beam aspect ratio (length/width) was significantly smaller in glaucoma eyes than normal eyes (p≤0.04) (Fig 2).
The smaller average pore size and beam aspect ratio may contribute to a stiffer pressure-induced strain response of the LC. In contrast, the greater curvature and beam tortuosity should produce a more compliant strain response. Computational modeling is needed to estimate the effects of the curvature and LC network structure on the strain response.
This is a 2021 ARVO Annual Meeting abstract.
Figure 1. Morphological analysis of the SHG imaged volume of a human LC showing: (a) the maximum projection of the SHG volume, (b) a binary mask of the LC collagen network, (c) pores in one slice of the SHG volume, (d) anterior-most points of the SHG volume, and a 5th order polynomial surface fit.
Figure 2. Comparing the specimen average (a) mean curvature, (b) tortuosity, (c) beam aspect ratio, and (d) average pore size of the LC of normal (n=10) and glaucoma eyes (n=16) using an unpaired t-test. The mean curvature and tortuosity were higher in glaucoma eyes than normal eyes (p≤0.04), while beam aspect ratio and average pore size were lower in glaucoma eyes than normal eyes (p≤0.04).
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