Label-free optical fundus angiography based on programmable hyperspectral imaging

Retinal vasculature, as the sole deep vascular network within the human body that can be non-invasively observed, is closely associated with various retinal and systemic disorders. However, conventional fundus imaging techniques often suffer from inadequate contrast or rely on invasive contrast agents to visualize fine retinal vessels, hemorrhages, and exudates, thereby posing great challenges in screening or diagnosing fundus diseases at their early stages. In this study, we report a label-free optical fundus angiography method based on programmable hyperspectral imaging, in which fundus images with high-contrast retinal blood vessels can be captured in a snapshot by exposing fundus tissues under specific spectrally coded illumination. Using a self-developed programmable light source, such specific spectrally coded illumination is multiplexed with specific intensities at different wavelengths under the guidance of spectral post-processing algorithms. This enables the preservation of key spectral bands that can maximize the differences between the retinal blood vessels and other fundus tissues. In such a manner, the proposed method can select the wavelengths of interest during fundus imaging in a snapshot, in contrast to numerical wavelength selection after acquiring the full wavelengths of conventional spectroscopic fundus imaging techniques; thus, the time-consuming acquisition of a three-dimensional spectral dataset and spectral post-processing can be avoided. Through evaluations on a model eye and ex vivo porcine eyes, the proposed label-free optical fundus angiography method shows significant enhancement in the image contrast of retinal blood vessels compared to conventional fundus imaging, thus is expected to benefit early and more precise diagnosis of fundus diseases.