Autofluorescence of the diabetic and healthy human cornea in vivo at different excitation wavelengths

Corneal autofluorescence is higher in diabetes mellitus patients with retin opathy than in healthy subjects. In this study, the excitation spectra of c orneal autofluorescence of diabetic patients and healthy controls in the ra nge 365 nm-480 nm were compared in an attempt to identify the fluorophores responsible for corneal autofluorescence in health and disease (diabetes). Spectral measurements (from one eye) were recorded from five patients with proliferative diabetic retinopathy and five age-matched healthy controls, u sing a modified commercial scanning fluoro-photometer with a mercury are or a tungsten halogen lamp as excitation light source in combination with int erference filters (excitation wavelengths: 365, 405, 420, 430, 436, 440, 45 0, 470 and 480 nm; bandwidth: 10 nm). Fluorescence emission was measured in the range 532 nm-630 nm. The sensitivity of the modified fluorophotometer was calibrated by using the excitation spectrum of fluorescein as a referen ce. The corneal excitation efficiency of the diabetic patients was higher than that of the healthy controls at each wavelength investigated (Mann-Witney t est P < 0.0005). The ratio between the mean values of both groups was equal for each excitation wavelength (mean ratio 1.9 +/- 0.12 S.D., P > 0.2), su ggesting that the excitation spectra were equal, This indicates that the sa me fluorophores are responsible for the corneal autofluorescence in both gr oups. The shapes of the excitation spectra suggest; the involvement of flav ins, NAD(P)H, and at least one other, as yet unidentified, fluorophore. (C) 1999 Academic Press.