Corneal biomechanical properties are influenced by several factors, including intraocular pressure, corneal thickness, and
viscoelastic responses. Corneal thickness is directly proportional to tissue hydration and can influence corneal stiffness,
but there is no consensus on the magnitude or direction of this effect. We evaluated the influence of corneal hydration on
dynamic surface deformation responses using optical coherence elastography (OCE). Fresh rabbit eyes (n=10) were
prepared by removing the corneal epithelium and dropping with 0.9% saline every 5 minutes for 1 hour, followed by
20% dextran solution every 5 minutes for one hour. Corneal thickness was determined from structural OCT imaging and
OCE measurements were performed at baseline and every 20 minutes thereafter. Micron-scale deformations were
induced at the apex of the corneal tissue using a spatially-focused (150μm) short-duration (<1ms) air-pulse delivery
system. These dynamic tissue responses were measured non-invasively with a phase-stabilized swept source OCT
system. The tissue surface deformation response (Relaxation Rate: RR) was quantified as the time constant, over which
stimulated tissue recovered from the maximum deformation amplitude. Elastic wave group velocity (GV) was also
quantified and correlated with change in corneal thickness due to hydration process. Corneal thickness rapidly increased
and remained constant following epithelium removal and changed little thereafter. Likewise, corneal stiffness changed
little over the first hour and then decreased sharply after Dextran application (thickness: -46% [-315/682 μm]; RR: -
24% [-0.7/2.88 ms-1]; GV: -19% [-0.6/3.2 m/s]). Corneal thickness and corneal stiffness (RR) were well correlated (R2
= .66). Corneal biomechanical properties are highly correlated with tissue hydration over a wide range of corneal
thickness and these changes in corneal stiffness are quantifiable using OCE.
Michael D. Twa, Srilatha Vantipalli, Manmohan Singh, Jiasong Li, and Kirill V. Larin, "Influence of corneal hydration on optical coherence elastography," Proc. SPIE 9693, Ophthalmic Technologies XXVI, 96930V (Presented at SPIE BiOS: February 14, 2016; Published: 4 March 2016); https://doi.org/10.1117/12.2210756.
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