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Valery Vinzent Wittwer, Amira M Eltony, Peng Shao, Seok-Hyun Yun, Beatrice E Frueh, Theo Gunther Seiler, Theo Seiler; In vivo Brillouin shift as a function of age in human cornea. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4322.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the age dependence of the Brillouin frequency shift in the central cornea in vivo in healthy subjects at 780 nm optical wavelength.
Brillouin measurements were made in the central corneas (< 2 mm from the pupil center) of 102 healthy eyes (Caucasian origin, 68 subjects, 49% female, aged 29-82 years, with mean 48 ± 16 years) with a clinically-viable Brillouin imaging system. Inclusion criterion is normal appearing corneas, with less than ± 3 diopters refractive correction, normal corneal topography (no irregular bow-tie, no skewed axis, no scar or other irregularities), and no history of eye diseases, except presbyobia and/or cataract. Eyes that underwent corneal surgery or eyes with pathologies of the anterior ocular segment were not included. Measurements were taken at room temperature (20 – 24°C), with a laser power of 5 mW on the cornea surface. Axial scans over a range of 1.2 mm with a step size of 30 μm were conducted. The Brillouin shift measured in the anterior stroma was averaged over 5 axial scans.Data analysis was performed with Prism 6.1 (GraphPad software, La Jolla, California, USA).
The mean Brillouin frequency shift across all ages was 5.726 GHz (SD = 0.015 GHz). Despite significant intersubject variation, a trend towards increasing Brillouin shift with age was observed, with a rate of increase of about ~ 5 MHz/decade (r2 = 0.23), which implies viscoelasticity increase of corneal tissue with age in humans.
Although the person-to-person variation is large, we observe a pattern of rising Brillouin frequency shift at 780 nm optical wavelength with age, which suggests growing corneal stiffness. This trend is consistent with prior in vitro studies showing a stiffening effect with age in ex vivo human corneas via direct stress-strain measurement (A. Elsheikh et al., CER 32(1), 2007).
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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