Imaging depth extension of optical coherence tomography in rabbit eyes using optical clearing agents

Signal Improved ultra-Fast Light-sheet Microscope (SIFT) for large tissue imaging

Light-sheet fluorescence microscopy (LSFM) in conjunction with tissue clearing techniques enables morphological investigation of large tissues faster and with excellent optical sectioning. Recently, cleared tissue axially swept light-sheet microscope (ctASLM) demonstrated three-dimensional isotropic resolution in millimeter-scaled tissues. But ASLM based microscopes suffer from low detection signal and slow imaging speed. Here we report a simple and efficient imaging platform that employs precise control of two fixed distant light-sheet foci to carry out ASLM. This allowed us to carry out full field of view (FOV) imaging at 40 frames per second (fps) which is a four-fold improvement compared to the current state-of-the-art. In addition, in a particular frame rate, our method doubles the signal compared to the current ASLM technique. To augment the overall imaging performance, we also developed a deep learning based tissue information classifier that enables faster determination of tissue boundary. We demonstrated the performance of our imaging platform on various cleared tissue samples and demonstrated its robustness over a wide range of clearing protocols.

Recent progress in optical clearing of eye tissues

The growing need for viewing the detailed 3D structures of various tissues and organs requires advanced tissue processing and imaging techniques. However, light scattering by tissues hinders detailed structural observations. To overcome this, the emerging technique of "tissue optical clearing" has been flourishing in recent decades, providing excellent opportunities for imaging deep, micro-scale structures of various organs, or even of the whole body. In recent years, advanced tissue clearing techniques have been optimized for specific tissues and organs. Among these tissues, the eye is unique owing to its delicate structure and pigmented retinal epithelial cells, calling for more work on making these tissues "transparent". In this review, we searched Medline and Embase for studies published between January 2006 and August 2021 using the terms "tissue optical clearing", "ophthalmology", "eye", and "optical clearing agents", and we reviewed the publications on the optical clearing techniques of eye tissue from 2006 to the present, including both the clearing procedures and the subsequent analytical processes, thus gaining more insight into the application of tissue optical clearing in basic eye research. Furthermore, we discuss the future potential of optical clearing applications in clinical ophthalmology.