Episcleral Venous Fluid Wave: Intraoperative Evidence for Patency of the Conventional Outflow System

Purpose: To report the observation of a perilimbal and/or episcleral vessel fluid wave seen during trabectome surgery, newly termed episcleral venous fluid wave. Patients and Methods: In 4 consecutive patients undergoing phaco-trabectome surgery, the authors observed the nasal perilimbal and episcleral collector vessels for an anticipated wave of fluid adjacent to the trabeculotomy site. The wave of fluid was elicited during the irrigation and aspiration phase of cataract surgery at the time of low intraocular pressure with no infusion (foot pedal position 0) to maximum irrigation (foot pedal position 2), creating a maximal pressure gradient for balanced salt solution (BSS) to surge into the anterior chamber and potentially out of the newly cleaved canal venous collector system. Results: During the anterior chamber surge of BSS, the authors observed in 4 cases, 2 types of fluid waves, one episcleral and sectorial in distribution and the other through the perilimbal conjunctival vessels. There was a correlation between the location of retrograde reflux of blood into the anterior chamber during the low-pressure phase and a wave of BSS into the immediate adjacent collector. Conclusions: The authors believe the fluid wave signifies intra-operative structural patency of the conventional outflow system from the anterior chamber to the episcleral and conjunctival distal collectors. The fluid wave is a sign that the collector system is at least anatomically functional, however, not necessarily physiologically functional. The presence or absence of a fluid wave may better explain canal-based surgical outcomes and could be a prognostic indicator for success after a trabectome surgery.