Evaluating the Influence of the Lens Autofluorescence on Adaptive Optics Fluorescence Lifetime Imaging Ophthalmoscopy

Purpose: To assess the impact of lens autofluorescence on adaptive optics fluorescence lifetime imaging ophthalmoscopy (AOFLIO). Methods: Eighteen subjects aged 23 to 68 years with normal chorioretinal health and phakic lenses were imaged using a research-grade AOFLIO instrument. Retinal autofluorescence was excited with a pulsed laser with wavelength at 473 nm and detected in two spectral channels (500-560 nm and 560-720 nm). AOFLIO images were acquired from the foveal center to 10° nasal retina. Autofluorescence decay was modeled using bi-exponential and tri-exponential functions, with and without accounting for the early arrival of lens autofluorescence. The contribution of lens signal was evaluated in relation to age and retinal location. Results: The tri-exponential model that accounted for the early arrival of lens autofluorescence demonstrated superior agreement with measured decays. The amplitude coefficient of lens contribution was 3% to 4%. However, this component accounted for 19.4% to 29.0% of photon-weighted signals and resulted in a 22.8% to 42.9% overestimation of the mean retinal lifetime when uncorrected. The lens effect was more pronounced in the short spectral channel. The time shift parameter of lens signal was associated with age (P = 0.023) and correlated with axial length (P = 0.036). Conclusions: AOFLIO substantially suppresses lens autofluorescence; however, residual lens signal persists and can disproportionately bias retinal autofluorescence lifetime estimates. Accurate correction of lens contributions is essential for reliable AOFLIO measurements. Translational Relevance: Minimizing the impact of lens autofluorescence in AOFLIO ensures accurate assessments of metabolic status in the retina and retinal pigment epithelium.