Purpose
Fluorescence Lifetime Imaging Ophthalmoscopy (FLIO) allows in vivo measurement of fluorescence lifetimes of natural retinal fluorophores. It is a new imaging technique based on a Heidelberg Engineering Spectralis® system (Heidelberg Engineering, Germany). We used FLIO to characterize fluorescence lifetimes in patients with atrophic AMD (age related macular degeneration) and to investigate structural and metabolic changes within atrophic lesions.
Methods
Fluorescence lifetime measurements were conducted in retinae with atrophic lesions from patients suffering from dry AMD and from age matched healthy control eyes (mean age AMD patients: 78±8 years, mean age controls: 76±9 years). The fluorescence excitation wavelength was 473 nm and mean fluorescence lifetimes were measured in a short and in a long spectral channel (SSC: 498-560 nm and LSC: 560-720 nm resp.) by time-correlated single photon counting. Four distinct areas were analysed and compared: Fovea, lateral retina, within and next to atrophic lesions.
Results
Fluorescence lifetimes in retinae of patients with nonexudative AMD were generally longer compared with our age matched healthy control eyes. In both groups, the shortest fluorescence lifetimes were observed in the macula (Tm = 333 ps), followed by the lateral retina (Tm = 392 ps) and the optic nerve (Tm = 1748 ps). Within geographic atrophy lesions, fluorescence lifetimes were significantly longer than in unaffected retinal tissue with mean values of 979 ps. Also in the tissue surrounding atrophic areas, fluorescence lifetimes seemed to be slightly prolonged compared to the healthy tissue.
Conclusions
Fluorescence lifetime imaging (FLIO) measurement is a novel method to characterize structural changes in the retinae of patients with atrophic AMD. Longitudinal studies will be needed to assess the value of FLIO for detection of AMD disease progression.
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
412 age-related macular degeneration