Metasurface-based long working-distance OCT fiber-optic probe for high-resolution intraocular imaging

Subretinal and intravascular retinal injections are increasingly recognized as promising therapeutic approaches for retinal diseases, particularly in the delivery of gene therapies, stem cells, and neuroprotective agents. Despite their clinical potential, these procedures remain technically challenging due to the fragile retinal tissue, narrow safety margins, and the need for precise needle-tip localization during surgery. Conventional needle insertion during intraocular injections relies primarily on microscopic visualization and subjective judgment based on direct observation of the needle tip or its shadow. However, in the complex intraocular environment, it is often difficult to accurately determine the precise insertion depth, leading to uncontrolled subretinal penetration of the needle. Furthermore, because the refractive indices of intraocular fluids are close to that of optical fibers, conventional spherical fiber probes are unable to achieve effective light focusing, which results in poor image quality. In this study, we present a novel optical coherent tomography (OCT) for subretinal and retinal vascular injections. An A-line OCT module was incorporated at the needle tip to enable depth evaluation. In addition, a metasurface-based phase modulation technique was employed to achieve planar light focusing and imaging. The proposed method demonstrates the feasibility of precise subretinal and retinal vascular injections. Compared with conventional approaches, our system significantly improves injection accuracy.