A tunable Synthetic Vascularized Eye Fundus for patient-free retinal imaging validation

Abstract The validation of novel retinal imaging techniques and motion-correction algorithms is often constrained by biological variability and the lack of ground-truth data in \textit{in vivo} measurements. To address this limitation, patient-free validation platforms require standardized targets that mimic selected optical and structural properties of the human eye. Here, we present a Synthetic Vascularized Eye Fundus (SVEF), a perfusable and contrast-tunable microfluidic insert designed for ophthalmic eye phantom platforms. The SVEF features a high-density, retinal-like vascular network fabricated by soft lithography using a custom polydimethylsiloxane-zinc oxide (PDMS--ZnO) composite. This substrate acts as a bright, diffusely scattering background, while perfusion with hemoglobin solutions generates physiologically relevant absorbing vessel-like structures. By optimizing the hemoglobin concentration, we achieved a vessel-to-background contrast closely matching that of \textit{in vivo} human fundus images. We validated the SVEF as a robust structural reference for image registration, demonstrating accurate retrieval of imposed saccade-like micro-displacements and enabling the enhancement of multi-frame fluorescence imaging. Finally, we confirmed the compatibility of the device with biological assays by successfully integrating and imaging human iPSC-derived retinal neurons. The SVEF provides a reproducible, patient-free environment for benchmarking ophthalmoscopic systems, optimizing image-registration pipelines and supporting versatile \textit{in vitro} retinal experiments.