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Sunny Kwok, Manqi Pan, Yanhui Ma, Xueliang Pan, Nicholas Hazen, Jun Liu; Mechanical Deformation of Peripapillary Retina during Intraocular Pressure Elevation. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1630.
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© ARVO (1962-2015); The Authors (2016-present)
To map and quantify the peripapillary retina (PPR) deformation during intraocular pressure (IOP) elevation in human donor eyes using high-frequency ultrasound elastography.
Inflation tests were performed in 10 donor globes (age: 20-74 years old, 4 male and 6 female) while IOP was raised in 0.5 mmHg steps from 5 to 30 mmHg. Each eye was inflated twice to capture 2D scans of the posterior eye centered at the optic nerve head (ONH) along the nasal-temporal (NT) and superior-inferior (SI) axis using a 50MHz ultrasound probe (Vevo2100, VisualSonics). A correlation-based speckle tracking algorithm (Tang & Liu, JBME 2012) was used to compute displacements, and strains were calculated using least squares estimation. Radial, tangential, and shear strains were obtained by coordinate transformation. Peripapillary sclera (PPS) and PPR were manually segmented for regional analysis (Fig 1A, tan and pink, respectively). Regional strain analysis was conducted at IOP = 30 mmHg using paired t-test.
Localized high tangential and shear strains were present in PPR during IOP elevation (up to 5%, Fig 1B). On average, PPR had less radial compression (-0.55±0.25% vs -2.32±0.74%, p<0.001), greater shear (1.49±0.65% vs 1.13±0.32%, p=0.029), and similar levels of tangential stretch (0.29±0.19% vs 0.38±0.19%, p=0.13, Fig 2A) as compared to the PPS. Exploratory analysis showed no significant differences in strains between quadrants in either PPR or PPS (Fig 2B).
Peripapillary retinal damage is characteristic of glaucoma progression. Our findings showed that although PPR experienced minimal radial compression during IOP elevation, localized shear and stretch were substantial, which could contribute to mechanical damage in this region during IOP elevation. These results provide new insights into IOP-related mechanical insults to the neural tissue near the ONH, where glaucomatous damage initiates.
This is a 2021 ARVO Annual Meeting abstract.
Fig 1: A) An ultrasound image of the posterior eye from a human donor globe along the nasal-temporal (NT) axis. PPS (dashed tan) and PPR (solid pink) segmentation are shown. B) Radial, tangential, and shear strain maps in the PPR of this eye at 30 mmHg.
Fig 2: A) Comparison of average radial, tangential, and shear strains between PPR and PPS at 30 mmHg (* denotes p<0.05). B) Strains in PPR and PPS showed no significant differences across quadrants. S: superior, I: inferior, N: nasal, T: temporal.
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