Fig. 18. Circumferentially oriented deep scleral plexus visualization.

A microvascular cast of the outflow system. (A). The trabecular meshwork (TM) is between the black curved line and the orange Schlemm’s canal (SC) cast. White arrows indicate the location of collector channels (CC) arising from SC and connecting to a circumferentially oriented deep scleral plexus (CDSP), as is indicated by a thin dashed red line. The CDSP forms a relatively continuous communicating ring adjacent and parallel to SC. Intraseleral vessels exit the CDSP and pass through the sclera (blue arrows) to the surface of the eye where episcleral and aqueous veins are visible. Between SC and CDSP are long, thin layers of collagenous tissue that appear as septa in histologic and OCT sections. OCT and direct observation at the dissecting microscope reveal that the thin septa move in response to ciliary body tension and pressure gradient changes within SC. Septa movement causes the lumen of the CDSP to open and close, thus functioning as a pressure-dependent compressible chamber. (B) Schematic illustration from the microscope view through the cut corneal surface that reveals the uniform angle of exit of the CC from SC. A view of casts from the surface of the corneoscleral interface does not provide a view perpendicular to the sites where CC exit SC. The view looking along the axis of the exit sites inadvertently gives the impression that the collector channels course directly from SC to the episcleral veins. By looking through the cut corneal surface (C), the view is perpendicular to the CC exit sites as in (D), which is the orientation shown in the microvascular cast in (A). The orthogonal view (E) makes the typical CC connections with the CDSP apparent. Tissue Source 78-year-old Caucasian male. From Johnstone Glaucoma Laboratory, University of Washington. Review Video in Fig. 16 – CDSP Open and Close 1-s2.0-S1350946220300896-mmc5.mp4.