Compact Laser Doppler Flowmeter (LDF) Fundus Camera for the Assessment of Retinal Blood Perfusion in Small Animals

Abstract

PurposeNoninvasive techniques for ocular blood perfusion assessment are of crucial importance for exploring microvascular alterations related to systemic and ocular diseases. However, few techniques adapted to rodents are available and most are invasive or not specifically focused on the optic nerve head (ONH), choroid or retinal circulation. Here we present the results obtained with a new rodent-adapted compact fundus camera based on laser Doppler flowmetry (LDF).MethodsA confocal miniature flowmeter was fixed to a specially designed 3D rotating mechanical arm and adjusted on a rodent stereotaxic table in order to accurately point the laser beam at the retinal region of interest. The linearity of the LDF measurements was assessed using a rotating Teflon wheel and a flow of microspheres in a glass capillary. In vivo reproducibility was assessed in Wistar rats with repeated measurements (inter-session and inter-day) of retinal arteries and ONH blood velocity in six and ten rats, respectively. These parameters were also recorded during an acute intraocular pressure increase to 150 mmHg and after heart arrest (n = 5 rats).ResultsThe perfusion measurements showed perfect linearity between LDF velocity and Teflon wheel or microsphere speed. Intraclass correlation coefficients for retinal arteries and ONH velocity (0.82 and 0.86, respectively) indicated strong inter-session repeatability and stability. Inter-day reproducibility was good (0.79 and 0.7, respectively). Upon ocular blood flow cessation, the retinal artery velocity signal substantially decreased, whereas the ONH signal did not significantly vary, suggesting that it could mostly be attributed to tissue light scattering.ConclusionWe have demonstrated that, while not adapted for ONH blood perfusion assessment, this device allows pertinent, stable and repeatable measurements of retinal blood perfusion in rats.

Velocity measurements of heterogeneous RBC flow in capillary vessels using dynamic laser speckle signal

“…[1][2][3] Many optical methods have been developed to measure blood flow, including Doppler-based methods (e.g., laser Doppler flowmetry, Doppler optical coherent tomography, and photoacoustic Doppler), [4][5][6] RBC-tracking measurements [e.g., multiphoton laser scanning microscopy (MPLSM), retinal function imager (RFI)], 7,8 and laser speckle contrast imaging (LSCI). 9 Doppler-based methods require a prior knowledge of Doppler angle to recover axial velocity components.…”

High speed optical holography of retinal blood flow

“…Retinal blood flow plays a central role in the pathophysiology of many eye diseases [1], either through capillary occlusion, panretinal hypoperfusion or uneveness of flow distribution. Noninvasive analysis of retinal hemodynamics has been achieved through various coherent light schemes including standard laser Doppler velocimetry [2][3][4], spatial [5][6][7] and temporal [8][9][10] speckle contrast analysis, stroboscopic fundus cameras [11], functional optical coherence tomography [12,13] and its fullfield variant [14]. Each of these approaches has its own limits in terms of sensitivity, spatial and/or temporal resolution, or lateral field of view.…”