Retinal Vascular Reactivity as Assessed by Optical Coherence Tomography Angiography

Sam Kushner-Lenhoff; Bright  S. Ashimatey; Amir H. Kashani

doi:10.3791/60948

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Method Article

Retinal Vascular Reactivity as Assessed by Optical Coherence Tomography Angiography

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DOI:

10.3791/60948

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March 26th, 2020

Sam Kushner-Lenhoff¹ , Bright S. Ashimatey¹ , Amir H. Kashani¹^,²

¹Department of Ophthalmology, USC Roski Eye Institute, ²USC Ginsberg Institute for Biomedical Therapeutics, Keck School of Medicine of the University of Southern California

Summary

This article describes a method for measuring retinal vasculature reactivity in vivo with human subjects using a gas breathing provocation technique to deliver vasoactive stimuli while acquiring retinal images.

Abstract

The vascular supply to the retina has been shown to dynamically adapt through vasoconstriction and vasodilation to accommodate the metabolic demands of the retina. This process, referred to as retinal vascular reactivity (RVR), is mediated by neurovascular coupling, which is impaired very early in retinal vascular diseases such as diabetic retinopathy. Therefore, a clinically feasible method of assessing vascular function may be of significant interest in both research and clinical settings. Recently, in vivo imaging of the retinal vasculature at the capillary level has been made possible by the FDA approval of optical coherence tomography angiography (OCTA), a noninvasive, minimal risk and dyeless angiography method with capillary level resolution. Concurrently, physiological and pathological changes in RVR have been shown by several investigators. The method shown in this manuscript is designed to investigate RVR using OCTA with no need for alterations to the clinical imaging procedures or device. It demonstrates real time imaging of the retina and retinal vasculature during exposure to hypercapnic or hyperoxic conditions. The exam is easily performed with two personnel in under 30 min with minimal subject discomfort or risk. This method is adaptable to other ophthalmic imaging devices and the applications may vary based on the composition of the gas mixture and patient population. A strength of this method is that it allows for an investigation of retinal vascular function at the capillary level in human subjects in vivo. Limitations of this method are largely those of OCTA and other retinal imaging methods including imaging artifacts and a restricted dynamic range. The results obtained from the method are OCT and OCTA images of the retina. These images are amenable to any analysis that is possible on commercially available OCT or OCTA devices. The general method, however, can be adapted to any form of ophthalmic imaging.

Introduction

The metabolic demand of the retina is dependent on an adequate and constant supply of oxygen provided by a well-regulated system of arterioles, capillaries and venules¹. Several studies have demonstrated that the function of larger caliber human retinal vessels can be assessed in vivo with various physiologic²^,³^,⁴^,⁵ and pharmacologic⁶^,⁷ stimuli. In addition, abnormal function of this vascular system is common in retinal vascular diseases such as diabetic retin....