Dual optical coherence tomography and microscopy for topographical and cellular evaluation of the cornea

Abstract

Purpose : We investigate the feasibility of dual imaging of corneal tissue with optical coherence tomography (OCT) and Gabor-Domain Optical Coherence Microscopy (GDOCM) to simultaneously visualize corneal morphology in three dimensions and resolve cellular features.

Methods : Imaging of donor corneal tissues was conducted with the novel dual-mode imaging system. The corneas, which are stored in a PMMA viewing chamber after recovery from donors, were imaged through the container to avoid contamination. The OCT imaging modality was used to quantify corneal thickness and overall topography over a field of view of 10 mm x 10 mm. The GDOCM imaging modality was used to visualize cellular structures including endothelial cells over a maximum field of view of 3.7 x 3.7 mm² with isotropic resolution of <3 μm in 3D. A numerical flattening method was applied to the 3D GDOCM images to compensate for the natural curvature of the cornea and produce a view of the endothelial cells in a single en face view, which can be compared to the conventional output of specular microscopes commonly used at eye banks to assess cell count density. Automated cell counting with machine learning methods was applied to the GDOCM images to assess endothelial cell density in an unbiased manner.

Results : The thicknesses of the corneal layers were assessed with the OCT imaging modality; the GDOCM imaging modality demonstrated cellular resolution in all corneal layers. The cell counts automatically obtained with machine learning from the numerically flattened GDOCM images of the endothelium were compared with the gold standard of specular microscopy.

Conclusions : Corneal imaging was conducted for the first time with two modalities (GDOCM and OCT) in the same instrument. Non-contact imaging provides a volumetric field that enables quantification of key cellular features of corneal tissue. This label-free approach to imaging may help us to better understand changes occurring in disease states or with age over time.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

GDOCM images of an ex vivo human cornea (field of view 1 mm²) imaged through the viewing chamber. (a) 3D view. (b) Full-depth cross-sectional image showing the corneal layers. En face images of the middle (c) and posterior (d) stroma reveal stromal keratocytes (white arrows). (e) En face view of the epithelium. (f) En face view of the transition between stroma and endothelium, with endothelial cells visible. Bars are 100 μm.