Adaptive Optics Fluorescence Lifetime Imaging Ophthalmoscopy for Single-Cell-Resolved In Vivo Metabolic and Structural Imaging of the Human Retinal Pigment Epithelium.

Fluorescence lifetime imaging ophthalmoscopy permits in vivo assessment of retinal metabolism but has remained limited by insufficient cellular resolution in the human eye. Here we present adaptive optics-enhanced fluorescence lifetime imaging ophthalmoscopy (AOFLIO), a method for single-cell-resolved, in vivo structural and metabolic imaging of the human retinal pigment epithelium (RPE). Through real-time correction of ocular wavefront aberrations, precisely synchronized adaptive optics reflectance and lifetime image acquisition via a phase-locked loop-based timing architecture, and sub-pixel photon registration that localizes individual autofluorescence photons with high spatial precision, AOFLIO directly resolves the RPE cell mosaic and measures autofluorescence decay using the same photons, enabling direct structural-functional correlation at the single-cell level. We demonstrate single-cell RPE lifetime mapping in healthy subjects and reveal altered metabolic signatures and fine characterization of RPE metabolic in age-related macular degeneration. AOFLIO establishes a platform for cellular-scale metabolic imaging in the living human eye.