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Impressum
Time-resolved measurement of autofluorescence - a tool for detection of metabolism at fundus
Schweitzer D., Hammer M., Anders R.
Augenklinik der FSU Jena, Bereich Experimentelle Ophthalmologie, Jena
Goal: To find a method for discrimination of endogenous fluorophores
at living human fundus.
Method: Fluorescence lifetime was chosen for discrimination of
fluorophores. A laser scanner ophthalmoscope was developed, exciting fluorophores
by pulses of 300ps FWHM, a frequency of 77MHz, and a wavelength of 458nm
during the scanning process. The fluorescence light was detected in time
correlated single photon counting technique considering wavelengths greater
than 515nm. Applying the maximum likelihood criterion, a mono-exponential
approximation of the decay behaviour was reached with an error less than
10% collecting about 300 fluorescence photons only.
Results: At healthy eye, mean lifetime of 1.5ns was determined
in the para-papillary region and 5ns in the optic disc and at large vessels.
Evaluating histograms, peaks at 1.38ns and 2ns as well as around 3ns were
found, corresponding to lipofuscin (A2-E), FAD and probably to elastin
and collagen.
Conclusions: At first time, time-resolved measurement of autofluorescence
was demonstrated at the living human fundus. The detection of FAD (flavin
adenin dinucleotide), acting as prostetic group in citric acid cycle and
in oxidative phosphoryllation opens the possibility of non-invasive estimation
of metabolic state at cellular level.