Anterior chamber blood cell differentiation using spectroscopic optical coherence tomography

Abstract

There is great clinical importance in identifying cellular responses in the anterior chamber (AC) which can indicate signs of hyphema (an accumulation of red blood cells (RBCs)) or aberrant intraocular inflammation (an accumulation of white blood cells (WBCs)). These responses are difficult to diagnose and require specialized equipment such as ophthalmic microscopes and specialists trained in examining the eye. In this work, we applied spectroscopic OCT to differentiate between RBCs and subtypes of WBCs, including neutrophils, lymphocytes and monocytes, both in vitro and in ACs of porcine eyes. We located and tracked single cells in OCT volumetric images, and extracted the spectroscopic data of each cell from the detected interferograms using short-time Fourier Transform (STFT). A look-up table of Mie spectra was generated and used to correlate the spectroscopic data of single cells to their characteristic sizes. The accuracy of the method was first validated on 10um polystyrene microspheres. For RBCs and subtypes of WBCs, the extracted size distributions based on the best Mie spectra fit were significantly different between each cell type by using the Wilcoxon rank-sum test. A similar size distribution of neutrophils was also acquired in the measurements of cells introduced into the ACs of porcine eyes, further supporting spectroscopic OCT for potentially differentiating and quantifying blood cell types in the AC in vivo.