Autofluorescence lifetime measurements in images of the human ocular fundus

Measurements of the autofluorescence at the fundus prove to be an important tool in early diagnosis and in discovering the pathomechanism, e.g., in age-related macular degeneration. In addition to the action of lipofuscin in the aging process, flavines play an important role as prosthetic groups. As metabolic changes occur at cellular level, patient-specific optimized therapy should be possible according to endogenous fluorophores, before morphological alterations are manifest. As a first tool for the detection of dynamic autofluorescence, a laser scanner opthalmoscope will be presented permitting lifetime measurements at the living human eye-ground under extremely weak detectable light. Considering histograms of lifetimes after excitation at 457.8 nm and determined at the living human eye ground in parapapillary region, a lifetime (rho) approximately equal to 1.38nm was calculated most frequently in the long-wave emission range ((lambda) $GTR550 nm). This points to the main contribution of lipfuscin. If the emission range is extended down to 515 nm, components with longer lifetimes are additionally detectable. Lifetime measurements at a human fundus specimen confirmed the lifetime of 1.38nm in lipfuscin-rich pigment epithelium, whereas the mean lifetime of an intact fundus was 2.04ns. A comparison of lifetimes before, during, and after breathing 100% oxygen results in a quenching of the mean lifetime of 0.15ns by oxygen.