Visualization of three-dimensional microcirculation of rodents’ retina for study of critical illness using optical coherence tomography angiography

Abstract

Purpose : To demonstrate OCTA imaging of the rodent retina for volumetric visualization of microvascular blood flow; to quantitatively investigate the retinal and choroidal hemodynamic changes in rat sepsis and hemorrhagic shock models; to evaluate OCTA-derived microvascular flow metrics as a severity assessment tool for critical vascular conditions.

Methods : A prototype high-speed OCT system was developed using a wavelength-swept light source operating at a center wavelength of 1040 nm and an A-line rate of 240 kHz. Volumetric OCTA data was acquired in the rat retina over 3.2 mm×3.2 mm field of view (FOV) centered at the optic nerve head. In order to obtain relative blood flow speed information, repeated B-scans with 5 inter-scan time periods were acquired at the same position and their pairwise complex decorrelation were calculated. OCTA imaging was performed in rat models of sepsis and hemorrhagic shock to visualize the blood flow in the microcirculation of the retina and the choroid. OCTA-derived metrics representing blood flow speed and capillary density were used to investigate the hemodynamic changes in rat sepsis and hemorrhagic shock models.

Results : OCTA assessment of quantitative microvascular blood flow was validated in healthy rats. The relative blood flow speeds of retinal (Fig. 1A) and choroidal vessels (Fig. 1B) were mapped onto a color scale. The shadow artifacts of thick vessels in the retina appeared in choroidal angiograms (Fig 1C, D). Relative blood flow speeds in rat sepsis model imaged at 30 and 90 minutes after induction of sepsis as well as at baseline were measured using OCTA. While the retinal capillaries did not show a considerable flow speed change during the 90-minute period after induction of sepsis, the choroidal vessels manifested a clearly noticeable reduction in blood flow speeds after sepsis induction.

Conclusions : OCTA can assess relative blood flow speed changes in the rat retina and choroid. OCTA can be useful for monitoring microcirculation in critical vascular conditions.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Microvasculature (A,C) and relative blood flow speed (B, D) of the normal rat retina (A,B) and choroid (C,D). FOV is 3.2 mm x 3.2 mm and scale bar is 400 um.

 

Relative blood flow speed change in retinal and choroidal vessels in rat sepsis model. Blood flow index of retina and choroid in rat sepsis model decline after inducing sepsis.