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

Abstract

Purpose : We established retinal vein occlusion (RVO) model using argon laser and observed longitudinal changes in retinal blood flow (RBF) and microvasculature using Doppler optical coherence tomography flowmeter (DOCT flowmeter)and optical coherence tomographyangiography (OCTA).

Methods : Branch RVO (BRVO) was induced by Argon green laserphotocoagulation (PC) in 6 eyes of 6 cats.After successful occlusion of the retinal vein was confirmed with OCTA, RBFwas measured from a first-order retinal artery and vein by DOCT flowmeter, and microvascular changes around the occluded vessels (12x12mm and 3x3mm) was assessed by OCTA before (at baseline) and right after PC and 1, 4, 7, 14 days thereafter. Systemic and ocular parameters such as mean blood pressure (MABP), heart rate (HR), percutaneous oxygen saturation (SpO2), intra ocular pressure (IOP), ocular perfusion pressure (OPP) were monitored during the measurements. One-way analysis of variance (ANOVA) was used for repeated measurements, followed by post hoc comparisons with the Dunnett procedure.

Results : There were no significant differences in any systemic and ocular parameters before and after PC. Arterial RBF (aRBF) increased significantly on day 1 (160.6 ±21.1% vs baseline, P < 0.05) and decreased under the baseline level after day 1 through day 14. Venous RBF (vRBF) decreased right after PC (17.4 ±23.5 % vs baseline, P < 0.05) and then gradually increased afterwards, but did not return to the baseline level. OCTA disclosed dilatation of retinal venules immediately after PC to day 1. Collateral vessels began to form on day 4 and became matured on day 7. The collateral vessels were pruned on day 14, and formed as mature as normal retinal venule diameters.

Conclusions : Arterial RBF increased within 1 day after inducing RVO. However, both arterial and venous RBF ended up decreasing during the observation period. Venules gradually expanded to form collateral vessels after PC, suggesting that collateral vessels originate from existing capillary networks but not by angiogenesis. The feline RVO model, combined with retinal flow analysis, has possibilities to elucidate the pathogenesis of RVO.

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