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

Ken Y Lin,Sameh Mosaed

doi:10.18502/jovr.v14i3.4783

Ken Y Lin, Sameh Mosaed

Open Access

https://doi.org/10.18502/jovr.v14i3.4783

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Abstract

PurposeThere 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 in-vivo are lacking. This pilot study establishes an ex-vivo system to evaluate the use of a confocal laser microendoscope to noninvasively image episcleral vessels and quantify regional flow variation along the limbal circumference.MethodsA 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.ResultsVascular 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).ConclusionThis study demonstrates for the first time that the fiber-optic CLE platform can visualize the episcleral vasculature with high resolution ex-vivo 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.

Highlights

The last several years have witnessed a rapidly rising interest in both developing new and modifying current minimally invasive glaucoma surgery (MIGS) methods
The salient findings of this study are that: (1) a confocal laser microendoscope can visualize episcleral vessels in cadaveric human eyes with minimal tissue manipulation, (2) in our ex-vivo system involving a perfused eye, the optimal time to image episcleral vessels is seven minutes after fluorescein injection into the anterior chamber, and (3) episcleral vessel diameter and density can be acquired in real-time and show that the inferior quadrants of the two human eyes in this study have statistically greater amount of fluorescence compared to the other quadrants
This study showed that the microendoscope was able to image surface episcleral vessels

Summary

Introduction

The last several years have witnessed a rapidly rising interest in both developing new and modifying current minimally invasive glaucoma surgery (MIGS) methods. Imaging of Episcleral Vessels in Human Eyes; Lin and Mosaed and tube shunt surgery, still have high complication rates, ranging from 27% in tube shunts to 74% in trabeculectomy.[1, 2] MIGS devices improve the outflow by bypassing or ablating the trabecular meshwork (TM) or creating new drainage routes into the suprachoroidal space.[3] Clinical studies so far show that most MIGS procedures display improved safety profiles over traditional procedures. The most common complications are temporary hyphema and transient rise in intraocular pressure (IOP) in the early postoperative period, occurring in 3–10% of Trabectome[4] and 2% of iStent patients.[5, 6]

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