Abstract:

Objective To observed the microstructures of the trabecular meshwork (TM) outflow pathways of rats using the two-photon confocal imaging technique without tissue fixation and staining. Design Experimental study. Participants The six SD rats. Methods Six rats were randomly divided into two groups (group A and group B). After being sacrificed, the intact eyeball of the rat (group A) was used to acquire the longitudinal section imaging data of the TM outflow pathways. The left eyes of the SD rats in group B were dissected for the cross section and sagittal plane of the TM outflow pathways imaging，and the other eyes was used as the control group. Through the anterior chamber of the eye, the self-built two-photon confocal imaging system (the excitation wavelength of 950 nm, lateral resolution of 0.3 μm and axial resolution of 1.5 μm) was used to image the microstructures of the TM and adjacent tissues from different directions. And the relation between the average cross-sectional diameter of Schlemm’s canal and the imaging depth based on image processing was quantitatively investigated. Main Outcome Measures The imaging depth of the TM outflow pathways from different directions, the structural features of the TM and the average cross-sectional diameter of Schlemm’s canal. Results The imagings of longitudinal section, cross section and sagittal structural features of the TM and the adjacent tissues were obtained based on two-photon confocal microscope. The fibers of TM seem to be heterogeneous with depth increases. The fibers of the deep TM were densely arranged, and the formed pores were small; the fibers of the shallow trabecular meshwork were interlaced, and the formed pores were large to facilitate the outflow of aqueous humor. The average cross-sectional diameter of the Schlemm’s canal was varied from 34 μm to 68 μm in the imaging depth range from 190 μm to 215 μm below the limbus. Conclusion Our research provides a trans-scleral imaging method to visualize the microstructure of the TM outflow pathways, which laid a methodological basis for further understanding of aqueous humor outflow dynamics in the TM outflow pathways.

Key words: trabecular meshwork, two-photon confocal microscope, Schlemm’s canal, glaucoma