  Anterior uveitis is the most common form of intraocular inflammation, and one
of its main signs is the presence of white blood cells (WBCs) in the anterior
chamber (AC). Clinically, the true composition of cells can currently only be
obtained using AC paracentesis, an invasive procedure to obtain AC fluid
requiring needle insertion into the AC. We previously developed a spectroscopic
optical coherence tomography (SOCT) analysis method to differentiate between
populations of RBCs and subtypes of WBCs, including granulocytes, lymphocytes
and monocytes, both in vitro and in ACs of excised porcine eyes. We have shown
that different types of WBCs have distinct characteristic size distributions,
extracted from the backscattered reflectance spectrum of individual cells using
Mie theory. Here, we further develop our method to estimate the composition of
blood cell mixtures, both in vitro and in vivo. To do so, we estimate the size
distribution of unknown cell mixtures by fitting the distribution observed
using SOCT with a weighted combination of reference size distributions of each
WBC type calculated using kernel density estimation. We validate the accuracy
of our estimation in an in vitro study, by comparing our results for a given
WBC sample mixture with the cellular concentrations measured by a hemocytometer
and SOCT images before mixing. We also conducted a small in vivo quantitative
cell mixture validation pilot study which demonstrates congruence between our
method and AC paracentesis in two patients with uveitis. The SOCT based method
appears promising to provide quantitative diagnostic information of cellular
responses in the ACs of patients with uveitis.
