High–Speed Ultrahigh–Resolution Full–Field Optical Coherence Tomography: Application to Anterior Segment Imaging in Rats

Abstract

Abstract: : Purpose: A new instrument that performs high–speed ultrahigh–resolution full–field optical coherence tomography (FF OCT) has been used to examine ocular tissue of the rat. Methods: The FF OCT set–up is based on a Linnik microscope, i.e. a Michelson interferometer with identical microscope objectives in both arms, illuminated by a Xenon arc source. A high resolution high speed CMOS camera records a series of interferometric images which are combined to display en face tomographic images in real time (250 frames / s). The use of full–field illumination and two–dimensional detection on the CMOS array replaces the point by point scanning of conventional OCT. Imaging in the en face orientation permits the use of high numerical aperture (NA) microscope objectives, which improve the transverse resolution of the instrument. High axial resolution is achieved thanks to the short source coherence length. We achieve isotropic spatial resolution of ∼1 µm. Results: We present images obtained in the anterior segment of the rat of corneal layers and the crystalline lens. The instrument captures images in the en face direction, allowing visualization of individual cellular layers. The resolution capability of our instrument permits cell quantification. In particular, the visualization of the epithelial and endothelial layers of the cornea and the fiber organization in the crystalline lens is made possible. Conclusions: The ultrahigh resolution of our instrument allows cellular level imaging, and the en face orientation of the images provides a detailed view of a single layer at a time so that individual cells and fiber structures can be distinguished and quantified. The use of a simple arc lamp rather than a sophisticated femtosecond laser source, as used in other ultrahigh–resolution OCT systems, makes our instrument robust, reliable and easy to use. The high–speed acquisition of the instrument makes it suitable for in vivo measurements. The system is currently under adaptation for use on human eyes.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: non-clinical • anterior segment