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Martin Hammer, Lynn Zweifel, Lukas Kreilkamp, Lydia Sauer, Rowena Schultz, Regine Augsten, Daniel Meller; Spectral and lifetime characteristics of drusen autofluorescence in age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3243. doi: https://doi.org/.
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Drusen, a hallmark of age-related macular degeneration (AMD), are known to show autofluorescence (AF) which is different from that of lipofuscin. Here we combine spectral and lifetime data of drusen AF in vivo.
28 patients with non-exudative AMD and no geographic atrophy were included. Fundus AF in a 30° retinal field was investigated with the Heidelberg Engineering Spectralis® fluorescence lifetime imaging ophthalmoscope (FLIO), detecting the temporal decay of the fluorescence in a short (498-560 nm; Ch1) and a long (560-720; Ch2) wavelength channel upon excitation with <100 ps laser pulses at 473 nm. The amplitude weighted mean fluorescence lifetime tm was calculated from a three-exponential approximation of the decay. The spectral ratio sr of fluorescence emission in ch1 and ch2 was calculated. Drusen were identified from color fundus photographs and segmented in the AF images within the inner and outer ring of the standard ETDRS-grid centered at the macula.
The lifetimes tm of drusen were significantly longer than that of RPE (all drusen (N=28): Ch1: 267 vs. 264.3ps, p=0.023, Ch2: 329.4 vs. 324.3ps p=0.023 hard drusen (N=12): Ch1: 278,7 vs. 264.3ps, p=0.015, Ch 2: 334.3 vs. 328.1ps, p=0.034, and soft drusen (N=23): Ch1: 271.4 vs. 264.3ps, p=0.089, Ch2: 329.1 vs. 322.4, p=0.016). Furthermore, drusen fluorescence was green-shifted compared to that of RPE (all drusen: sr=0.57 vs. 0.51, p<0.0005, hard drusen: sr= 0.54 vs. 0.50, p=0.006, and soft drusen: sr=0.57 vs. 0.51, p<0.0005, see fig. 1 for example). No correlations between tm and sr were found.
Drusen contain fluorophores which are different from that of RPE lipofuscin. As these can be investigated by FLIO in vivo, this can help to understand the nature of sub-RPE drusenoid deposits and might give additional diagnostic information on their role in AMD progression. Fluorescence lifetimes and spectral ratio give independent information on drusen fluorophores.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig. 1: Dry AMD with soft drusen. Top left: fundus photograph, top right: autofluorescence, bottom left: fluorescence lifetime (500-560nm), bottom left: spectral ratio
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