Assessment of Retinal and Choroidal Blood Flow Changes Using Laser Doppler Flowmetry in Rats

Abstract

Purpose: A new noninvasive laser Doppler flowmetry (LDF) probe (one emitting fiber surrounded by a ring of eight collecting fibers, 1-mm interaxis distance) was tested for its sensitivity to assess the retinal/choroidal blood flow variations in response to hypercapnia, hyperoxia, diverse vasoactive agents and following retinal arteries photocoagulation in the rat.

Materials and Methods: After pupil dilation, a LDF probe was placed in contact to the cornea of anesthetized rats in the optic axis. Hypercapnia and hyperoxia were induced by inhalation of CO₂ (8% in medical air) and O₂ (100%) while pharmacological agents were injected intravitreously. The relative contribution of the choroidal circulation to the LDF signal was estimated after retinal artery occlusion by photocoagulation.

Results: Blood flow was significantly increased by hypercapnia (18%), adenosine (14%) and sodium nitroprusside (16%) as compared to baseline values while it was decreased by hyperoxia (-8%) and endothelin-1 (-11%). Photocoagulation of retinal arteries significantly decreased blood flow level (-45%).

Conclusions: Although choroidal circulation most likely contributes to the LDF signal in this setting, the results demonstrate that LDF represents a suitable in vivo noninvasive technique to monitor online relative reactivity of retinal perfusion to metabolic or pharmacological challenge. This technique could be used for repeatedly assessing blood flow reactivity in rodent models of ocular diseases.

KEYWORDS::

• Blood flow
• Microcirculation
• Choroid
• Retina
• Rodents

ACKNOWLEDGEMENTS

The authors would like to thank Charles Riva (Medical School, University of Lausanne, Switzerland) and Rodney Gush (Moor Instruments, UK) for a careful reading and discussion of the manuscript, Florence Dotigny for her technical assistance and Denis Latendresse for the graphic work. SH and MP are recipients of a Studentship from the Vision Research Network (FRSQ) and the Foundation Fighting Blindness, respectively. This work was presented at the ARVO Meeting, Fort Lauderdale, 2010 and International Society for Eye Research, Montreal, 2010.

Declaration of interest: This study was supported by the Vision Research Network (FRSQ).