Modern Diagnostic Techniques for the Assessment of Ocular Blood Flow in Myopia: Current State of Knowledge

Abstract

Myopia is the most common refractive error and the subject of interest of various studies assessing ocular blood flow. Increasing refractive error and axial elongation of the eye result in the stretching and thinning of the scleral, choroid, and retinal tissues and the decrease in retinal vessel diameter, disturbing ocular blood flow. Local and systemic factors known to change ocular blood flow include glaucoma, medications and fluctuations in intraocular pressure, and metabolic parameters. Techniques and tools assessing ocular blood flow include, among others, laser Doppler flowmetry (LDF), retinal function imager (RFI), laser speckle contrast imaging (LSCI), magnetic resonance imaging (MRI), optical coherence tomography angiography (OCTA), pulsatile ocular blood flowmeter (POBF), fundus pulsation amplitude (FPA), colour Doppler imaging (CDI), and Doppler optical coherence tomography (DOCT). Many researchers consistently reported lower blood flow parameters in myopic eyes regardless of the used diagnostic method. It is unclear whether this is a primary change that causes secondary thinning of ocular tissues or quite the opposite; that is, the mechanical stretching of the eye wall reduces its thickness and causes a secondary lower demand of tissues for oxygen. This paper presents a review of studies assessing ocular blood flow in myopes.

Introduction and Overview on Myopia: A Clinical Perspective

“…Although some authors have tried to use analysis of flow voids or signal voids in the choriocapillaris to quantify the area taken up by the microvasculature [143,144], the data pertaining to myopic patients are but insufficient [145]. Looking into the future, there is, however, incipient research suggesting that the comprehension of blood supply and changes in vasculature from the anterior to the posterior segment of the myopic eye is crucial to the understanding of the disease [146][147][148][149].…”

Imaging in myopia: potential biomarkers, current challenges and future developments

“…Different authors used, however, different image analysis approaches to quantify signal voids and no common protocol is currently available. Nonetheless, emerging reports suggest that understanding the blood supply and changes in vasculature from the anterior to the posterior segment of the myopic eye92–94 is important in understanding the disease 95…”

Macular and peripapillary vessel density in myopic eyes of young Chinese adults

“…However, some of these techniques have certain limitations; for example, fluorescein angiography is an invasive examination and Doppler imaging mainly focuses on large vessels rather than microvasculature. 10,11 With the utilisation of optical coherence tomography angiography (OCT-A), highresolution images and quantified data from different retinal layers are now easily accessible in a non-invasive manner. However, measurement of vessel density relies on a comparison against population-specific normative data.…”