Correlation of Episcleral Venous Fluid Wave With Type and Extent of Canal-Based Surgery
Narrative Responses:
Purpose
There is no visible outcome marker for canal surgery. Besides measuring IOP, how do we know if our canal procedure is working as intended? The episcleral venous fluid wave (EFW) is evidence of intraoperative patency of the collector system. Authors determined if the EFW correlates with the type of canal-based procedure.
Methods
Ten exemplary patients undergoing various canal-based surgeries were evaluated for the episcleral venous fluid wave during the irrigation-aspiration phase of surgery. Video footage of the wave was recorded for each case to determine the location, extent and degree of flow into the nearby aqueous veins to determine if the flow correlated with device insertion or cleavage of the canal.
Results
The authors found a correlation between the type and extent of canal-based surgery and the episcleral venous fluid wave. Flow into aqueous veins was largely limited to nearby collector channels for stents. A more widespread wave was noted when a greater circumference of the canal was cleaved or opened. There was also flow into the nearby episcleral venous plexus, not just the large veins.
Conclusion
The authors believe the episcleral venous fluid wave is an intraoperative tool to visualize the collector system. It serves as anatomic confirmation of accurate device placement and correlates with extent of canal cleaved, but does not confirm physiologic improvement in outflow. We await better outcome markers for canal surgery.