July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Regional Differences in Deformation of the Posterior Eye During IOP Elevation
Author Affiliations & Notes
  • Elias Pavlatos
    Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States
  • Yanhui Ma
    Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States
  • Keyton Clayson
    Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States
    Biophysics Interdisciplinary Group, The Ohio State University, Columbus, Ohio, United States
  • Xueliang Pan
    Department of Biomedical Informatics, The Ohio State University, Columbus, Ohio, United States
  • Jun Liu
    Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States
    Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, Ohio, United States
  • Footnotes
    Commercial Relationships   Elias Pavlatos, None; Yanhui Ma, None; Keyton Clayson, None; Xueliang Pan, None; Jun Liu, None
  • Footnotes
    Support  NEI Grant RO1EY020929
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 2034. doi:
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      Elias Pavlatos, Yanhui Ma, Keyton Clayson, Xueliang Pan, Jun Liu; Regional Differences in Deformation of the Posterior Eye During IOP Elevation. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2034.

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

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Abstract

Purpose : To measure the 3D deformation of the optic nerve head (ONH) and peripapillary tissues (PPT) in response to IOP elevation.

Methods : Nine whole globes (5 human donor, mean age 72 ± 8 y.o.; 4 porcine) were measured by ex vivo inflation testing. Extraocular tissues were cut away and the optic nerve was trimmed to be flush with the peripapillary sclera. The globes were secured in a custom-built holder with two spinal needles inserted at the equator of the globe, and the holder was immersed in saline. Two 20G needles were inserted into the anterior chamber to control and monitor IOP. Inflation testing was performed with IOP steps of 15, 17, 19, 22, 25, and 30 mmHg. At each IOP level, a 3D ultrasound scan was obtained by acquiring successive B-mode images at 32 µm intervals. The scan covered a 10 mm2 region of the posterior eye centered on the ONH. A 3D ultrasound speckle tracking algorithm was used to compute spherical displacements and strains. Paired t-tests were used to analyze regional differences in deformation at 30 mmHg.

Results : The ONH showed larger outward radial displacements compared to the PPT in porcine eyes (40.4 ± 21.5 µm vs 6.5 ± 15.4 µm, p = 0.006) but not in humans (13.7 ± 18.9 µm vs 14.6 ± 19.9 µm, p = 0.27). The human ONH exhibited more compressive radial strain than the PPT (-2.05 ± 0.69% vs -1.84 ± 0.61%, p = 0.019). Meridional strains were higher in the ONH than the PPT for porcine eyes (0.49 ± 0.25% vs 0.13% ± 0.11%, p = 0.009). In human eyes, more outward radial displacement was measured in the anterior region compared to posterior (30.3 ± 22.4 µm vs -0.4 ± 17.2 µm, p = 0.0001 in PPT; 26.1 ± 21.2 µm vs 1.3 ± 16.7 µm, p = 0.0002 in ONH). All three strains were larger in the anterior human PPT (-3.02 ± 1.12% vs -0.71 ± 0.33%, p = 0.004 for radial; 0.29 ± 0.24% vs 0.10 ± 0.15%, p = 0.004 for circumferential; 0.41 ± 0.17% vs 0.09 ± 0.07%, p = 0.005 for meridional). The same result was found in the human ONH (-4.21 ± 1.56% vs 0.11 ± 0.68%, p = 0.004 for radial; 0.37 ± 0.46% vs 0.24 ± 0.46%, p = 0.04 for circumferential; 0.63 ± 0.48% vs 0.24 ± 0.40%, p = 0.0005 for meridional).

Conclusions : Measurement of the mechanical behavior of the posterior eye revealed significant regional differences. In human eyes, anterior ONH was the region most sensitive to IOP change which may be important in glaucoma etiology.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Displacement and strain vs IOP for different regions.

Displacement and strain vs IOP for different regions.

 

Deformation maps for 75 y.o. human donor.

Deformation maps for 75 y.o. human donor.

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