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17.09.2020 -New Publication on the Comparison of algorithms

to suppress artifacts from the natural lens in fluorescence lifetime imaging ophthalmoscopy (FLIO)

Fluorescence lifetime imaging ophthalmoscopy (FLIO) has developed as a new diagnostic tool in ophthalmology. FLIO measurements are taken from 30° retinal fields in two spectral channels (short spectral channel (SSC): 498–560 nm, long spectral channel (LSC): 560–720 nm). Because of the layered structure of the eye, the detected signal is an interaction of the fluorescence decay of the anterior part and of the fundus. By comparing FLIO measurements before and after cataract surgery, the impact of the natural lens was proven, despite the application of a confocal laser scanning (cSLO) technique. The goal of this work was to determine the best algorithmic solution to isolate the sole fundus fluorescence lifetime from the measured signal, suppressing artifacts from the natural lens. Three principles based on a tri-exponential model were investigated: a tailfit, a layer-based approach with a temporally shifted component, and the inclusion of a separately measured fluorescence decay of the natural lens. The mean fluorescence lifetime τm,12 is calculated using only the shortest and the intermediate exponential component. τm,all is calculated using all three exponential components. The results of tri-exponential tailfit after cataract surgery were considered as reference, because the implanted artificial can be assumed as non-fluorescent. In SSC, the best accordance of τm,all of the reference was determined with τm,12 of the tailfit before surgery. If high-quality natural lens measurements are available, the correspondence of τm,12 is best with τm,all of the reference. In LSC, there is a good accordance for all models between τm,12 before and after surgery. To study the pure fundus fluorescence decay in eyes with natural lenses, we advices a triple-exponential tailfit and fluorescence lifetime τm,12 as τm,12 corresponds well with the mean fluorescence lifetime τm,all of eyes with fluorescence-less artificial intraocular lenses.

Dietrich Schweitzer, Jens Haueisen, Jakob L. Brauer, Martin Hammer, Matthias Klemm:
Comparison of algorithms to suppress artifacts from the natural lens in fluorescence lifetime imaging ophthalmoscopy (FLIO)

Biomedical Optics Express Vol. 11, Issue 10, pp. 5586-5602 (2020)

Contact: Dr.-Ing. Matthias Klemm

Fluorescence intensity (A and B) and fluorescence lifetimes (C, D, and E) before cataract surgery (A, C, and D), and after cataract surgery (B and E). C (M2) and E (Reference) show the mean fluorescence lifetime τm,all using three exponential components while D (M1) shows τm,12 using only the first two exponential components. There is a good correspondence between τm,all after cataract surgery with τm,12 before cataract surgery. The color scaling is identical for all fluorescence lifetimes.