Assessing the effects of riboflavin/UV-A crosslinking on porcine corneal mechanical anisotropy with optical coherence elastography

Abstract

In this work we utilize optical coherence elastography (OCE) to assess the effects of UV-A/riboflavin corneal collagen crosslinking (CXL) on the mechanical anisotropy of porcine corneas at various intraocular pressures (IOP). There was a distinct meridian of increased Young's modulus in all samples, and the mechanical anisotropy increased as a function of IOP and also after CXL. The presented noncontact OCE technique was able to quantify the Young's modulus and elastic anisotropy of the cornea and their changes as a function of IOP and CXL, opening new avenues of research for evaluating the effects of CXL on corneal biomechanical properties.

Assessment of the influence of viscoelasticity of cornea in animal ex vivo model using air‐puff optical coherence tomography and corneal hysteresis

“…The CCT was thinner by ~34% once the entire CXL treatment was completed. A similar effect was observed in both in vivo as well as in vitro studies . It is most likely that this effect was associated with the corneal dehydration caused by dextran .…”

“…The load may be applied in a contact or noncontact way, for example, by the gonioscopy lens , mechanical indentation , pulsed laser , sound waves , airborne ultrasound and the air puff from the tube or needle . The performance of the OCT‐based elastography has been demonstrated in in vitro corneal tissues , in ex vivo eye models as well as in in vivo studies with patients . OCT allowed to monitor the geometrical changes of the cornea due to the increased IOP.…”

Optical coherence elastography – OCT at work in tissue biomechanics [Invited]

“…For example, Fig. 9 shows elastograms of the estimated Young's modulus of the cornea in two porcine eyes taken from the same animal, for which cornea 1 is untreated (control) and cornea 2 is treated by ultra-violet (UV) light-based cross-linking while cycling intra-ocular pressure (IOP) [187]. The data clearly indicate anisotropic characteristics, which become more pronounced at higher IOP.…”

Applanation optical coherence elastography: noncontact measurement of intraocular pressure, corneal biomechanical properties, and corneal geometry with a single instrument

“…anisotropy on the OCE measurements. 24 The Young's modulus was estimated from the group velocity using the surface wave equation. 16,25 Figure 3 plots the IOP as measured by Appl-OCE (horizontal stripe) and rebound tonometry (vertical stripe) along with the stiffness of the cornea (blue) estimated by OCE.…”

“…The surface wave equation does not take into account the corneal viscoelastic nonlinearity, 25,28 corneal curvature and thickness, 29 aqueous humor, 30 dispersion of the elastic wave, 31,32 or corneal mechanical anisotropy. 24,33 Additionally, the limited spatial and temporal data points resulted in the large variance in measured corneal biomechanical properties at 20 mmHg (stiff conditions), and the limited bandwidth of the air-pulse induced waves (below 1 kHz) combined with limited number of data points prevented dispersion analysis of the elastic wave. There are still several steps for improvement, which are the focus of our future work.…”