Characterizing dynamic properties of retinal vessels in the rat eye using high speed imaging

The dynamic properties of retinal vessels including pulse wave propagation and pulsatility index provide new perspective in retinal hemodynamic analysis. In this study we utilize a high speed imaging system to capture these characteristics in the rat eye for the first time.

Retinal video images of 9 Wistar-Kyoto (WKY) rats were captured at a rate of 250 frames per second for 10s with a 50° field of view using a high speed camera (Optronis, Kehl, Germany). Two recordings were taken from each rat at the same sites for repeatability analysis. The electrocardiogram (ECG) was measured simultaneously with retinal images. Arterial retinal pulse wave velocity (rPWV) and arterial/venous pulse amplitude were calculated from recorded images. Arterial measurements were repeated in another normotensive strain of the same age (Sprague-Dawley, n=4).

The average WKY rPWV was 11.4 ± 6.1 cm/s. The differences between repeated measures were not significant (-2.8 ± 2.9 cm/s, p=0.2). Sprague-Dawley animals had a similar rPWV (9.8 ± 2.2 cm/s, p=0.61). The average arterial and venous pulse amplitude was 7.1 ± 1.5 μm and 8.2 ± 2.0 μm respectively. There was a positive correlation between rPWV and heart rate in the WKY groups (r(2)=0.32). A positive correlation was also obtained between arterial and venous diameter and their pulse amplitude (r(2)=0.67 and r(2)=0.37 respectively).

rPWV was associated with heart rate. Higher pulsation amplitude was also correlated with larger vessel diameter. High speed imaging of retinal vessels in the rat eye provides an accurate and robust method to study dynamic characteristics of these vessels and their relationship with ocular and systemic abnormalities.