Evaluation of a non-invasive fluorescence technique as a marker for diabetic lenses in vivo

A fluorescence spectrometer has been constructed to study in vitro and in vivo fluorescence of human lenses. This instrument can measure fluorescence emission spectra, which can be useful in the characterisation of the lens endogenous fluorophores and evaluation of the feasibility of fluorescence measurement as a non-invasive marker for diabetes. The spectrometer allows determination of the optimum excitation and emission wavelengths, which can be used in simpler instrumentation for monitoring purposes.

To est the application in such studies a homogeneous group of type II diabetic subjects and normal controls was studied. For each subject the fluorescence emission spectra was measured using a spectrometer prototype consisting of a modified slit lamp coupled to a optical multichannel analyser (OMA). The incorporation of narrow-band filters allows the selection of three different excitation wavelengths: 404 nm, 436 nm and 485 nm.

With both in vitro and in vivo measurements, no significant differences were found between diabetic and normal lenses concerning the wavelength of maximum emission of fluorescence. However, the spectra (lambda(exc)=436 nm) between 480 and 550 nm were better defined with diabetic lenses. Using ratios of fluorescence intensity at two different wavelengths (490/610, 510/610, and 550/610) allows for good discrimination between normal controls and diabetic patients. The use of ratios largely removes the effects due to attenuation of excitation light and emitted fluorescence.

The non-invasive evaluation of lens fluorescence is proposed as early indicator of ocular complications associated with diabetes.