Interpretation of measurements of dynamic fluorescence of the eye

First pathological alterations occur at cellular level, most in metabolism. An indirect estimation of metabolic activity in cells is measurement of microcirculation. Measurements of tissue autofluorescence are potentially suited for direct investigation of cellular metabolism. Besides redox pairs of co-enzymes (NADH-NAD, FADH2-FAD) several other fluorophores are excited in tissue. In addition, a number of anatomical structures are simultaneously excited, when investigating the eye-ground. In this study, spectral and time resolved comparison was performed between purified substances, single ocular structures and in vivo measurements of the time-resolved autofluorescence at the human eye. In human eyes, the ageing pigment lipofuscin covers other fluorophores at the fundus in long - wave visible range. Applying lifetime measurements, weakly emitting fluorophores can be detected, when the lifetimes are different from the strongly emitting fluorophore. For this, the autofluorescence was excited at 468 nm and detected in two spectral ranges (500 nm-560 nm, 560 nm-700 nm). In tri-exponential fitting, the short lifetime corresponds to retinal pigment epithelium, the mean lifetime corresponds probably to neural retina and the long lifetime is caused by fluorescence of connective tissue.