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.
Highlights
Laser Doppler flowmetry (LDF) is a technique widely used to assess red blood cell (RBC) perfusion in tissues
While not adapted for optic nerve head (ONH) blood perfusion assessment, this device allows pertinent, stable and repeatable measurements of retinal blood perfusion in rats
Several LDF prototypes have been developed in animals to evaluate blood perfusion in various vascular beds of the eye, such as the retina, the optic nerve head (ONH) and the choroid [2]
Summary
Laser Doppler flowmetry (LDF) is a technique widely used to assess red blood cell (RBC) perfusion in tissues. Noninvasive techniques of ocular blood perfusion measurement have previously been developed, including LDF [8], laser speckle [9], optical coherence tomography (OCT) [10], optical microangiography (OMAG) [11], magnetic resonance imaging (MRI) [12], the scanning laser ophthalmoscope-particle tracking method [13] and scanning LDF [14]. Many of these techniques require specific and expensive equipment for animal studies (OCT, MRI, OMAG) and highly qualified operators. Some techniques require the sacrifice of the animal such as those using (14C)-iodoantipyrine [17], N-Isopropylp- [14C]-iodoamphetamine [14C]-IMP tracer [18] or radiolabeled microspheres [19]
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