Heartbeat-induced Ocular Pulsation in the Murine Cornea revealed by Phase-Sensitive Visible-Light OCT

Abstract

Purpose : Ocular pulsations in corneal tissue occur physiologically due to heartbeat-induced IOP fluctuations. Monitoring of spatially-resolved pulsative amplitudes and frequencies with phase-sensitive OCT can provide an insight into pathophysiological impairments of the investigated tissue that are not detectable in conventional intensity-based OCT images. Here we present a novel method to measure heartbeat induced compression and relaxation in the cornea with phase-sensitive visible-light (vis) OCT.

Methods : A vis-OCT prototype was developed for in vivo high-resolution imaging of the murine cornea. The system operates at an A-scan rate of 100 kHz and provides an axial and lateral resolution of 2.2 µm and 2.3 µm, respectively. Reduction of bulk motion in the phase difference images was achieved by translational image registration based on intensity correlation in consecutive high-resolution intensity images. Further data processing steps were performed on the registered phase difference images to extract spatially-resolved axial motion relative to the epithelial surface layer. For experimental validation, the central cornea of an anesthetized C57BL/6 mouse was continuously imaged with 500 consecutive B-scans repeated at the same location over a total acquisition time of 5 seconds.

Results : Figure 1B shows the time progression of depth resolved displacement amplitudes from the cornea section in Figure 1A. Displacement units are given in nm per frame repetition time(10ms). The motion signal in Figure 1C was extracted by averaging the displacement values in the stromal layer at approximately 50 µm to 100 µm in cornea depth. The averaged displacement maxima in this region are below 10nm. The corresponding frequency analysis in Figure 1D accentuates the periodic character of the pulsative motion signal. The frequency peaks at 2 Hz and 4 Hz could correspond with breathing and heart rate of the anesthetized animal.

Conclusions : Measurement of pulsative motion in the cornea, as it has been demonstrated in our work, can provide the basis for the establishment of a passive elastography method and might be used for further investigations of biomechanical tissue properties in various corneal pathologies.

This abstract was presented at the 2024 ARVO Imaging in the Eye Conference, held in Seattle, WA, May 4, 2024.