Abstract
Purpose :
Corneal densitometry based on the analysis of optical coherence tomography (OCT) speckle properties is gaining attention. Since speckle parameters can be used as disease biomarkers it is important to investigate any potential confounding factors that may affect them. Normally, the stroma is observed via the epithelium. Consequently, the aim of this work is to assess whether epithelial integrity is a confounding factor in the assessment of stromal densitometry.
Methods :
OCT data collected from 11 enucleated porcine eyeballs were analyzed. Each eyeball was imaged 3 times before and 3 times after the epithelial debridement (epi-on, epi-off, respectively). During the examination the eyeballs were regularly moistened with phosphate-buffered saline. Speckle contrast ratio (CR) was estimated for different corneal depths using a moving region of interest (ROI) with width = 1 mm, depth = 100 μm and a step downwards = 10 μm. CR data was analyzed to compare the same stromal region in epi-on and epi-off mode (Fig. 1A and 1B).
Results :
CR in corneal stroma in the epi-on mode is statistically significantly correlated to that in the epi-off mode (r = 0.65; p < 0.001). However, the results suggest there exists a bias introduced by the epithelial layer causing the CR values to be overestimated when viewed via the epithelium (Fig. 1C). Additionally, the difference in CR values between epi-on and epi-off changes with the sample depth (Fig. 1D).
Conclusions :
In this animal study we have shown that epithelium plays a significant role that should be taken into consideration when investigating stromal corneal tissue properties, such as corneal densitometry. The confounding effect of this additional layer is not straightforward to overcome. The character of the epithelium influence seems to be complex and needs more investigation. Further work is also necessary to assess how other technologies are affected by epithelial integrity (e.g., Scheimpflug imaging) and to investigate the influence of epithelial health on corneal densitometry readings.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.