Episcleral Venous Outflow: A Potential Outcome Marker for iStent Surgery

Area of Science:

• Ophthalmology
• Glaucoma Surgery
• Medical Device Evaluation

Background:

• iStent surgery is a common procedure for glaucoma management.
• Assessing the long-term functionality of iStents is crucial for patient outcomes.
• Current outcome markers may not fully capture the physiological impact of iStent implantation.

Purpose of the Study:

• To propose episcleral venous outflow (EVO) as a novel outcome marker for iStent surgery.
• To introduce and validate a simple grading scale for EVO.
• To investigate the association between EVO grades and postoperative intraocular pressure (IOP), medication burden, and iStent patency.

Main Methods:

• A retrospective cohort study of 151 eyes undergoing iStent-phacoemulsification.
• Collected preoperative and postoperative data including IOP, medication use, and iStent status.
• Assessed EVO using a proposed grading scale (0: no flow, 1+: faint flow, 2+: marked flow) and analyzed associations with clinical outcomes.

Main Results:

• Eyes with marked laminar flow (2+) showed significantly lower postoperative IOP and reduced medication burden at 1 year compared to those with no flow (0).
• iStent patency was strongly associated with greater EVO (OR=4.73), while obstruction was linked to reduced flow.
• No stent malpositioning was observed in the study cohort.

Conclusions:

• Episcleral venous outflow (EVO) is a physiologically relevant marker for iStent surgery outcomes.
• The proposed EVO grading scale is practical for clinical use and aids in assessing iStent functionality.
• Further prospective studies are recommended to validate the EVO grading scale in iStent surgery assessment.