Clinical Evidence of Valvelike Structures in Schlemm Canal and Their Anatomic Links Detected by Optical Coherence Tomography.

PURPOSE

To determine if the valvelike structures in Schlemm canal detected by OCT in the clinic setting are comparable to established intracanalicular ex vivo laboratory images.

DESIGN

Retrospective observational case series

PARTICIPANTS

Pre- and postoperative angle images of 10 human subjects from Glaucoma Associates of Texas who underwent interventional valve-enhancing trabeculotomy (iVEnT) were compared to 24 human and nonhuman primate (NHP) ex vivo eyes from the Johnstone Laboratory.

METHODS

To determine the origin of the newly observed in vivo OCT intracanalicular structures, the OCT images were compared to 6 known laboratory outflow images from the Johnstone Laboratory: (1) hinged collagen flaps (HCFs), (2) Schlemm canal (SC) inlet valve (SIV), (3) circumferential vascular channels (CVCs), (4) collector channel ostium (CCO), (5) septum of the outer wall of SC (OWSC), and (6) SC.

MAIN OUTCOME MEASURES

A comparison of the shape, location, and dimensions of the 6 ex vivo structures to the undefined in vivo clinic OCT angle structures.

RESULTS

Two hundred seventy outflow laboratory images from 15 human and 9 nonhuman primates (NHPs) were sourced from the Johnstone Laboratory to define the measurements of the 6 key outflow structures that served as the comparators for the undefined in vivo OCT structures of 277 clinic angle images. The shape and location of the clinic in vivo valvelike structures in SC and their anatomic links correlated with the shape and location of all 6 known ex vivo laboratory structures. A limited number of preoperative eyes also demonstrated valvelike intracanalicular structures. The in vivo OCT dimensions on average were greater than ex vivo measurements, likely because of tissue shrinkage from scanning electron microscopy (SEM) processing.

CONCLUSION

This is the first clinical OCT evidence of valvelike structures in Schlemm canal, which were visualized in all 10 postoperative eyes. Based on structural and dimensional similarities, the authors hypothesize that the 3 in vivo clinical OCT structures closely resemble the SIV, HCF, and CVC. Our preliminary results bridge the gap from the laboratory to the clinic and add support to the addition of these 3 structures to the anatomy of the living human aqueous outflow system.