June 2020
Volume 61, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2020
The structure and ex vivo inflation response of the human lamina cribrosa: analysis for differences between glaucoma and normal eyes
Author Affiliations & Notes
  • Cameron Czerpak
    Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
  • Yik Tung Tracy Ling
    Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
  • Harry A Quigley
    Ophthalmology, Johns Hopkins Wilmer Eye Institute, Baltimore, Maryland, United States
  • Thao D Nguyen
    Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
  • Footnotes
    Commercial Relationships   Cameron Czerpak, None; Yik Tung Tracy Ling, None; Harry Quigley, None; Thao Nguyen, None
  • Footnotes
    Support  Public Health Service Research Grant EY021500, Microscopy and Imaging Core Module, Wilmer Core Grant for Vision Research, National Science Foundation Grant CMMI-1727104
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 1004. doi:
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      Cameron Czerpak, Yik Tung Tracy Ling, Harry A Quigley, Thao D Nguyen; The structure and ex vivo inflation response of the human lamina cribrosa: analysis for differences between glaucoma and normal eyes. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1004.

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      © ARVO (1962-2015); The Authors (2016-present)

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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.

 

Figure 1. Analysis of SHG image volume of a representative human LC: (a) Maximum projection of the SHG volume, (b) circumferential strain for inflation from 5-45 mmHg calculated from DVC, (c) map of the junctions of collagen beams, (d) anterior-most points of the SHG volume, and a 5th order polynomial surface fit.

Figure 1. Analysis of SHG image volume of a representative human LC: (a) Maximum projection of the SHG volume, (b) circumferential strain for inflation from 5-45 mmHg calculated from DVC, (c) map of the junctions of collagen beams, (d) anterior-most points of the SHG volume, and a 5th order polynomial surface fit.

 

Figure 2. (a) Mean curvature is higher in glaucoma eyes. (b) Axial length is longer in glaucoma eyes. (c) The specimen averaged circumferential strain is lower in glaucoma eyes. (d) Pore density is not different in glaucoma eyes.

Figure 2. (a) Mean curvature is higher in glaucoma eyes. (b) Axial length is longer in glaucoma eyes. (c) The specimen averaged circumferential strain is lower in glaucoma eyes. (d) Pore density is not different in glaucoma eyes.

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