Episcleral Venous Fluid Wave Correlates with Trabectome Outcomes: Intraoperative Evaluation of the Trabecular Outflow Pathway

Purpose: To determine whether the characteristics of an intraoperative episcleral venous fluid wave (EVFW), a potential indicator of trabecular outflow patency, correlates with Trabectome (NeoMedix Corp, Tustin, CA) outcomes.

Design: Retrospective, observational study.

Participants: A total of 68 eyes of 49 patients with glaucoma who underwent phaco-Trabectome (63 eyes) or Trabectome alone (5 eyes).

Methods: The EVFW was evaluated in a masked fashion for wave degree (0-4) and clock hours (0-6). A diffuse EVFW (4, 5, 6 clock hours) was a near complete blanching of the episcleral vasculature, and a poorly defined wave was minimal change in the vasculature. Patients were grouped into wave categories to determine whether there was a correlation with postoperative intraocular pressure (IOP). Patients requiring further glaucoma surgery were considered failures.

Main outcome measures: Degree and extent of EVFW, IOP, and glaucoma medications.

Results: For all eyes, there was a statistically significant correlation between wave clock hours and postoperative IOP at month 1 (P = 0.043) and month 3 (P = 0.002), but not a statistically significant correlation at month 6 (P = 0.12) or 1 year (P = 0.86). A strong correlation was found among IOP, medications, and EVFW in eyes with an extensive EVFW when compared with eyes with a poorly defined EVFW. At 12 months, the mean IOP in the extensive EVFW group was 13.3±2.7 mmHg on 1.4±1.2 medications compared with an IOP of 18.4±3.1 mmHg on 2.9±0.9 medications in the poorly defined group (both P = 0.001). Overall, 5 of 68 eyes (7%), required further glaucoma surgery. Eyes with a poorly defined EVFW had a higher likelihood of further glaucoma surgery (36%).

Conclusions: The EVFW is an intraoperative gauge of patency through the trabecular outflow pathway. Absence of the EVFW implies obstruction in the collector channel-intrascleral aqueous outflow pathway, preventing flow to the visible episcleral veins. In contrast, eyes with a diffuse EVFW had sufficient flow through their collector channels, had a lower IOP, required fewer glaucoma medications, and had a lower requirement for further glaucoma surgery. The characteristics of an EFVW may be able to predict surgical outcomes after Trabectome surgery.