Longitudinal Monitoring of Ocular Blood Flow Dynamics in Experimental Rabbit Models

Abstract

Purpose : The rabbit retina model may provide a surrogate for human vascular, immune, and coagulation response. Monitoring ocular blood flow in the rabbit retina may offer insights on early pathological changes that precede anatomical vascular changes in a variety of ocular and systemic disease states. The purpose of this study was to assess repeatability of ocular blood flow (OBF) measurements obtained by XyCAM CRE, a noninvasive laser speckle-based imager in a rabbit model of longitudinal retinal imaging.

Methods : Bilateral laser speckle retinal imaging was conducted on 5 anesthetized male New Zealand white rabbits. Each rabbit underwent 2-3 days of imaging with at least 3 days in between. On each day of imaging, at least 3 distinct data sets (“sessions”) were acquired of 2 fields of view (FOV) on the nasal and temporal side of the optic disc respectively. During each imaging session, OBF data was acquired over six seconds spanning multiple cardiac cycles. Blood Flow Velocity Index (BFVI) values were averaged in fixed length segments of one retinal artery and one retinal vein on each of nasal and temporal FOVs. Repeatability of measurements was assessed by calculating coefficient of variation (CV) across multiple BFVI averages of the same vessel segment obtained across multiple cardiac cycles within each session (“intra-session CV”), across all acquired sessions (“inter-session CV), and across all days of imaging (“longitudinal CV”).

Results : Table I shows repeatability results for OBF in the major artery and vein within the nasal and temporal FOVs of the left and right eye. Mean intra-session CV for peak (0.84±0.13%) and dip (0.77±0.12%) velocity indices were less than 5%. Mean inter-session CV and intra-day peak velocity indices were 6.20±3.08% & 7.86±2.13%, respectively and dip velocity indices were 6.25±3.08%. & 7.91±2.13, respectively.

Conclusions : The rabbit retina laser speckle retina model has a less than 5% intra-session CV and less than 10% inter-session and intra-day CV, indicating it is a sufficiently repeatable measurement of ocular blood flow. This rabbit retina imaging model and technique can be effectively applied to different ocular disease states to determine how ocular blood flow may be altered before clinical signs of the disease become apparent. These data support the use of ocular blood flow as a relevant metric and potential surrogate for systemic radiation related injury.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.