Purchase this article with an account.
Michael Saheb Kashaf, Thao D. Nguyen, Harry A Quigley; IOP-Induced In Vivo Deformation and Strains in the Human Optic Nerve Head using OCT. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2516.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
We measured in vivo deformation and mechanical strain in the optic nerve head (ONH) in glaucoma patients using optic coherence tomography (OCT) scans of the ONH before and after a short-term change in intraocular pressure (IOP).
Persons treated for open angle glaucoma underwent imaging by radial ONH OCT scans obtained before and 20 minutes after IOP increase produced by tight-fitting swimming goggles or before and after IOP decrease by laser suturelysis. Bruch’s membrane opening and the anterior lamina cribrosa (LC) border were manually marked. Digital volume correlation calculated 3D displacements within the LC, defined as tissue up to 250 µm posterior to anterior LC border. Displacements were used to calculate anterior lamina depth (ALD) change and LC strains. Generalized estimating equation models accounted for inclusion of both eyes in goggles patients.
In 20 eyes (12 persons, mean field MD= -2.6 dB), goggles-wearing increased mean IOP by 6.6 mm Hg (range 1-16) and produced -0.32 ± 0.71% mean compressive anterior-posterior LC strain (Ezz) (p=0.056). Suture lysis in 14 eyes (14 persons, mean field MD= -9.5 dB) decreased mean IOP by 13 mm Hg (range: 3-45) and produced +1.04 ± 1.37% mean tensile Ezz strain (p=0.010). Among suturelysis eyes, greater IOP change was associated with both larger Ezz strain (p=0.0005) and larger maximum principal strain (Emax; p=0.005). In the goggles group, Emax was significantly smaller with thicker peripapillary nerve fiber layer in corresponding inferior (p=0.05) and temporal (p=0.01) quadrants. In goggles eyes, a more normal visual field index was associated with a smaller maximum principal strain (p=0.04). ALD deepened among goggles eyes (mean = 3.8 ± 5.98 μm, p=0.011) and moved toward the vitreous after suturelysis (mean = 2.5 ± 5.93 μm, p=0.122). Greater IOP change was associated with greater ALD change in both goggles (p < 0.0001) and suturelysis (p=0.04) eyes.
Modest short-term IOP alterations led to measurable changes in anterior LC depth and tissue strains. The association between field damage and strain in goggles wearers may indicate that strains are preexisting correlates of glaucoma susceptibility, or, that strain changes result from glaucomatous injury. Longitudinal studies are planned to elucidate these issues.
This is a 2021 ARVO Annual Meeting abstract.
This PDF is available to Subscribers Only