Abstract
Purpose :
Microscopic optical coherence tomography (mOCT) has an imaging resolution of 1 µm in all voxel dimensions but individual epithelial cells are difficult to resolve due to lack of scattering contrast. Adding dynamic contrast processing to mOCT (dmOCT) scans enables visualization of individual cells and quantification of subcellular motion to evaluate cell function. We propose this technique as a novel method of evaluating the ocular surface after exposure to a toxic chemical, benzalkonium chloride (BAK).
Methods :
Ex-vivo cross-section images were acquired with a custom-built frequency domain mOCT system. A dynamic contrast (dmOCT) scan consists of 150 B-scans with 512 A-scans. Five sets of dmOCT scans were consecutively taken at each imaging time point per eye. Eyes were explanted from healthy adult (21 weeks) C57BL/6 mice (n = 6; 6 control group, 6 BAK group), glued to cell culture dishes, and immersed in cell culture media. After baseline images were acquired in all eyes, BAK group media was replaced with 0.005% BAK media. Eyes were imaged every 30 min and were incubated at 37C between imaging sessions. Total epithelium and stroma thickness were measured from a single mOCT B-Scan while measures of cell motility and hue were acquired from dmOCT scans. Cellular motility was calculated by the normalized intensity standard deviation over time. Hue was created from the frequency spectra of the dmOCT signal with the blue channel for slow (0-0.5 Hz), green for medium (0.5-5 Hz), and red fast motion (5-25 Hz).
Results :
After 30min exposure to 0.005% BAK, epithelium thickness increased and cell motility decreased compared to controls (Fig 1). Basal cell motility decreased after 60min exposure and the hue shifted red after 90min. Stroma thickness did not significantly swell until 120min exposure to BAK.
Conclusions :
dmOCT allows us to view the behavior of the cornea epithelium under toxic stress due to BAK, showing changes to subcellular motion and swelling of the extracellular matrix.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.