BACKGROUND: Alterations in the equilibrium of redox pairs of co-enzymes give information about the metabolic state in the citric acid cycle as well as in the respiratory chain. Fluorescence properties are different between the reduced and oxidised states of co-enzymes so that a change of the oxygen partial pressure can be sensitively detected in the tissue. Therefore, it was investigated whether the autofluorescence of co-enzymes is detectable in the living fundus. METHOD: The provocation of metabolism was realised by inspiration of 100% oxygen. The time-resolved autofluorescence was detected by a single photon counting technique. The decay behaviour of autofluorescence was approximated by a bi-exponential model. For evaluation of the results, histograms of decay times tau(1) and tau(2) were calculated in defined ranges around the macula and optic disc before, during, and after inhaling oxygen. RESULTS: The calculated decay times corresponded in the macula to the decay times of FAD and NADH(+) given in the literature. Connective tissue in the optic disc also showed fluorescence. CONCLUSIONS: Changes in the histograms of decay rates demonstrate that provocation of metabolism is detectable by measurement of time-resolved autofluorescence. This method reveals the evaluation of metabolism at the cellular level as a new diagnostic possibility.
BACKGROUND: Alterations in the equilibrium of redox pairs of co-enzymes give information about the metabolic state in the citric acid cycle as well as in the respiratory chain. Fluorescence properties are different between the reduced and oxidised states of co-enzymes so that a change of the oxygen partial pressure can be sensitively detected in the tissue. Therefore, it was investigated whether the autofluorescence of co-enzymes is detectable in the living fundus. METHOD: The provocation of metabolism was realised by inspiration of 100% oxygen. The time-resolved autofluorescence was detected by a single photon counting technique. The decay behaviour of autofluorescence was approximated by a bi-exponential model. For evaluation of the results, histograms of decay times tau(1) and tau(2) were calculated in defined ranges around the macula and optic disc before, during, and after inhaling oxygen. RESULTS: The calculated decay times corresponded in the macula to the decay times of FAD and NADH(+) given in the literature. Connective tissue in the optic disc also showed fluorescence. CONCLUSIONS: Changes in the histograms of decay rates demonstrate that provocation of metabolism is detectable by measurement of time-resolved autofluorescence. This method reveals the evaluation of metabolism at the cellular level as a new diagnostic possibility.
Authors: Matthew G Field; Victor M Elner; Donald G Puro; Jason M Feuerman; David C Musch; Rodica Pop-Busui; Richard Hackel; John R Heckenlively; Howard R Petty Journal: Arch Ophthalmol Date: 2008-07