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Dietrich Schweitzer, Lydia Deutsch, Matthias Klemm, Susanne Jentsch, Martin Hammer, Jens Dawczynski, Ulrich Alfons Mueller; Detection Of Early Metabolic Alterations In Diabetes Mellitus By Time-resolved Fundus Autofluorescence (FLIM). Invest. Ophthalmol. Vis. Sci. 2011;52(14):1753.
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To detect metabolic changes before morphologic alterations are visible. Such results can be used for patient-specific treatment and control of therapy.
FLIM was measured in 62 diabetics (mean 62.5±14years) having no signs of diabetic retinopathy. As control, 33 healthy subjects (mean 56±20years) were used. FLIM measurements were performed by the Jena Lifetime Laser Scanner Ophthalmoscope. Laser pulses (70ps duration, 80MHz repetition rate, 0.1mW) excited FLIM in a 30degree field. FLIM was detected by time-correlated single photon counting in 2 spectral channels (CH1=490-560nm, CH2=560-700nm). The decay of fluorescence intensity was 3-exponentially fitted. As result, histograms of amplitudes Ai, lifetimes Ti, and relative contribution Qi=Ai•Ti were calculated. Statistical comparison was done by Holm-Bonferroni method. Here, the range of the fitting parameters is divided in n intervals. A significant difference exists between distinctive values of fitting parameters of diabetics and healthy subjects, if the error probability, calculated by Wilcoxon test, is lower than a given error probability e.g. 5%, divided by the number n of intervals.
Most sensitive for discrimination of diabetics and healthy subjects are measurements in CH1. In A1 interval (50-100%, width 1%) significant differences were found for 14 values (73 - 92%), for A2 (5-30%, width 1%) 4 values (5 - 14%), and for A3 (0-18%, 0.5% width) 21 values (1 - 17%). The lifetime T1 (30-120ps, width 10 ps) was significantly different only for 50 and 90 ps, for T2 (300-900ps, width 10 ps) at 640, 650, 660, and 670ps, and for T3 (2.3-7ns, 50 ps width) at 16 values (2,4 - 3.1ns). In Ch2, significant differences were found for A1 6 values (63 - 83%), for A2 at 25, 27, 29%, for A3 12 values (1- 8.5%). Significant differences were found for T1 at 100ps, no for T2, and for T3 at 3.1, 3.15, 3.2ns.
Differences in amplitudes and lifetimes of autofluorescence, predominantly in CH1, are probably caused by accumulation of advanced glycation end-products and by increased contribution of protein-bound NADH.
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