Blood flow analysis of retinal neovascularisations in a VLDLR mouse model using contrast-enhanced optical coherence tomography

Age-related macular degeneration (AMD) is a major cause of global blindness that affects millions worldwide. Certain forms of AMD cause neovascularisations (NVs), which form retinal-choroidal anastomoses. This disrupts healthy haemodynamic patterns, and early detection and treatment are crucial for preserving vision. Here, we employ a custom-built optical coherence tomography (OCT) imaging system to investigate these NVs in a very low-density lipoprotein receptor (VLDLR) knockout mouse model. Mice were imaged before, during, and after contrast agent injection, aiming to enhance our understanding of the NV haemodynamics. Doppler signal analysis techniques were employed to calculate flow velocities within individual NVs. Flow rates pre- and post-injection were determined based on these velocity measurements. Particle tracking was performed on two NVs for a comparative analysis with the Doppler velocity measurements. Both methods of measuring flow velocities showed good agreement post-contrast injection. The analysis of post-injection flow rates from the NVs revealed diverse behaviours. Some NVs exhibited stable flow rates over time, while others showed signs of instability, with flow rates changing substantially or even changing flow direction at different time points. Additionally, it was observed at multiple time points that flow from certain NVs moved from the choroid to the retina at the same time that other NVs displayed flow in the opposite direction. These observations suggest complex interactions between choroidal and retinal vascular networks in diseases like AMD. Further characterisation using contrast-enhanced Doppler OCT may improve our understanding of neovascular haemodynamics.