Multimodal optical elastography assessment of a murine collagen XII knockout

Abstract

Purpose : Measuring the biomechanical properties of the eye can be useful for understanding structure and assessing ocular health. In particular, the organization of the corneal stroma’s extracellular matrix is essential for vision. The presence of Collagen XII in the corneal stroma affects the corneal structure and has been hypothesized to affect biomechanical properties. Here, we use a multimodal optical elastography approach to measure the effect of Collagen XII on the biomechanical properties of the cornea.

Methods : The measurements were performed within 24 hours of eye enucleation (after overnight shipment from Tampa to Houston in corneal preservation media). Age and gender-matched wild type (WT) and collagen XII insufficient corneas were dissected with scleral ring intact and mounted on a closed loop intraocular pressure (IOP) control system. Measurements were taken from 10 mmHg to 25 mmHg in 5 mmHg increments. Figure 1 shows the air coupled ultrasound elastography (ACUS-OCE), heartbeat OCE (Hb-OCE), and Brillouin microscopy systems used to assess the mechanical properties of five corneas of each group. The corresponding Brillouin frequency shift, Lamb wave speed, and compressive strain measured from each technique respectively characterize the mechanical properties of the tissue.

Results : Results of the optical elastography measurements are shown in Figure 2. All measurement techniques show a distinct decrease in stiffness due to collagen XII insufficiency. Furthermore, both OCE techniques show an expected increase in stiffness as a function of IOP; however, this trend was absent in the Brillouin measurements.

Conclusions : Optical elastography can be used to measure the stiffness of the cornea as a function of IOP. Furthermore, measurements suggest that the presence of Collagen XII increases the stiffness of the corneal stroma. Future work will be geared towards the quantification of tissue biomechanical properties, as well as the investigation of tissue anisotropy.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

a) OCE system schematic used for both ACUS-OCE and Hb-OCE. b) Brillion microscopy system schematic.

 

a) Lamb wave speed as a function of IOP for WT and KO corneas. b) Compressive strain as a function of IOP for WT and KO corneas. c) Brillouin Frequency shift as a function of IOP for WT and KO corneas.