Aqueous Cell Differentiation in Anterior Uveitis Using Fourier-domain Optical Coherence Tomography

Abstract

 

Purpose

 

To determine the composition of aqueous inflammatory cells with Fourier-domain optical coherence tomography (OCT).

 

Methods

 

A 26 kHz Fourier-domain OCT system (RTVue, Optovue, Inc.) with 5 µm axial resolution was used to image cells both in vitro and in vivo. Leukocytes were separated from a human blood sample and sorted with a flow cytometer. Cell suspensions of neutrophils, lymphocytes and monocytes were placed into tubes and imaged with OCT. Custom designed software algorithms were developed to automatically identify, measure, and count cells in the OCT image. The axial width, peak intensity, and axial intensity sum of each cell type were measured. In the clinical study, the anterior chamber (AC) of anterior uveitis patients with active inflammation was imaged with OCT. Aqueous cells were detected and measured by the same automated software. The percentage composition of the aqueous cells was estimated by fitting its axial intensity sum distribution to a linear combination of neutrophil and lymphocyte (as representative of mononuclear cells) distributions.

 

Results

 

Neutrophils had the same apparent size as mononuclear cells, but were significantly brighter in OCT images (Table 1). Fourteen anterior uveitis patients were recruited and 19 eyes were included in the study. In 7 patients with HLA-B27 associated acute anterior uveitis or ankylosing spondylitis studied within 2 weeks of the flare onset, OCT showed that neutrophils were the predominant (>50%) cells in the AC. The one exception was a subject with bilateral disease, in which neutrophils dominated in the symptomatic eye and mononuclear cells dominated in the asymptomatic eye. In two patients with inflammatory bowel disease and a recent flare-up of uveitis, mononuclear cells predominated in the AC. Neutrophils were predominant in one case of endophthalmitis, and mononuclear cells predominated in one case of sarcoid. Two idiopathic subjects were characterized by neutrophils and another by lymphocytes in the AC.

 

Conclusions

 

The ability to differentiate AC inflammatory cells as neutrophils or mononuclear cells without resorting to an invasive aqueous tap provides a useful diagnostic test that could aid in of treatment decisions and understanding pathogenesis.

 

 

Table 1. In Vitro White Blood Cell Size and Reflectance Measurements by OCT

 

Keywords: 550 imaging/image analysis: clinical • 746 uveitis-clinical/animal model