Longitudinal Changes in Retinal Blood Flow in a Feline Retinal Vein Occlusion Model as Measured by Doppler Optical Coherence Tomography and Optical Coherence Tomography Angiography

Abstract

PURPOSE. We aimed to observe longitudinal changes in retinal blood flow (RBF) and structural transformations in capillaries using Doppler optical coherence tomography (DOCT) and optical coherence tomography angiography (OCTA) in a feline retinal blood occlusion (RVO) model. METHODS. RVO was induced by argon green laser photocoagulation (PC) in six eyes of six cats. RBF was measured at a first-order retinal artery and vein by a DOCT flowmeter, and structural changes in the capillaries around the occluded vessels (12 × 12 and 3 × 3 mm) were assessed by OCTA before (at baseline); immediately after PC; and on days 1, 4, 7, and 14 thereafter. Systemic and ocular parameters were monitored during the observation period. RESULTS. There were no significant differences in any systemic or ocular parameters before and after PC. Arterial RBF increased significantly on day 1 (160.6 ± 8.6% vs. baseline, P < 0.001) and decreased below baseline after day 1 through 14. Venous RBF decreased immediately after PC (17.4 ± 9.6% vs. baseline, P = 0.001) and then gradually increased afterwards, but did not return to baseline. OCTA showed dilatation of retinal venules immediately after PC to day 1. Collateral vessels began to form on day 4, had matured by day 7, and were pruned on day 14, which formed as mature as normal retinal venule diameters. CONCLUSIONS. With increasing arterial RBF within 1 day after inducing RVO, venules gradually expanded to form collateral vessels, suggesting that collateral vessels originate from existing capillary networks, not neovascularization.

Time course of collateral vessel formation after retinal vein occlusion visualized by OCTA and elucidation of factors in their formation

“…Wada et al. made similar observations in their experiments on feline RVO [ 14 ]. However, due to the characteristics of OCTA, when retinal blood flow is slow, it does not always depict the actual state of retinal blood flow.…”

“…Wada et al. utilized OCTA in a feline RVO model [ 14 ]. While they precisely described the vascular changes after PC, the feline model had limitations in the lack of antibodies against various proteins as well as unknown mRNA sequences that would enable further investigation.…”

“…OCTA is thus less invasive to the body than traditional angiographies especially for those with drug allergies. Although experience and information on OCTA in human clinical use has been gradually increasing [ 1 , 8 , 9 , 10 , 11 , 12 , 13 ], there have been very few examples of applying this technique to experimental animal models [ 14 ]. Through the use of OCTA, retinal blood vessels in a mouse RVO model can be imaged multiple times with less invasion.…”

“…Through the use of OCTA, retinal blood vessels in a mouse RVO model can be imaged multiple times with less invasion. Therefore, OCTA might be highly useful for evaluating vascular changes in animals over time [ 14 ]. Moreover, OCTA can separately visualize blood flow structures in the retinal blood vessels from multiple layers of the retina.…”

Multimodal Imaging of Microvascular Abnormalities in Retinal Vein Occlusion

“…Collateral vessels mature over 6 to 24 months after BRVO onset [9]. In contrast, previous animal studies have shown that collateral vessels were observed within 3 to 5 days after BRVO [84,96,97]. One study [97] found that collateral vessels developed from the preexisting capillary networks up to 4 days after laser-induced vein occlusion, matured by day 7, and were pruned on day 14 to a size similar to the original retinal vein.…”