Ab Externo Imaging of Human Episcleral Vessels Using Fiberoptic Confocal Laser Endomicroscopy.

PURPOSE

There is a growing interest in targeting minimally invasive surgery devices to the aqueous outflow system to optimize treatment outcomes. However, methods to visualize functioning, large-caliber aqueous and episcleral veins are lacking. This pilot study establishes an system to evaluate the use of a confocal laser microendoscope to noninvasively image episcleral vessels and quantify regional flow variation along the limbal circumference.

METHODS

A fiber-optic confocal laser endomicroscopy (CLE) system with lateral and axial resolution of 3.5 m and 15 m, respectively, was used on three porcine and four human eyes. Diluted fluorescein (0.04%) was injected into eyes kept under constant infusion. The microprobe was applied to the sclera 1 mm behind the limbus to acquire real-time video. Image acquisition was performed at 15-degree intervals along the limbal circumference to quantify regional flow variation in human eyes.

RESULTS

Vascular structures were visualized in whole human eyes without processing. Schlemm's canal was visualized only after a scleral flap was created. Fluorescent signal intensity and vessel diameter variation were observed along the limbal circumference, with the inferior quadrant having a statistically higher fluorescein signal compared to the other quadrants in human eyes ( < 0.05).

CONCLUSION

This study demonstrates for the first time that the fiber-optic CLE platform can visualize the episcleral vasculature with high resolution with minimal tissue manipulation. Intravascular signal intensities and vessel diameters were acquired in real-time; such information can help select target areas for minimally invasive glaucoma surgery (MIGS) to achieve greater intraocular pressure reduction.