title: Fluorescence/Raman intensity ratio for monitoring the pathologic state of human lens.
abstract: The authors have put quantitation of human lens fluorescence on a rational basis by using the accompanying Raman signal from lens protein as a normalization factor. The intensity ratio, Fluorescence/Raman (F/R), may be used to compare lenses of different ages when the exciting wavelength is long enough to give a measurable Raman signal. In younger lenses excited at 457.9 or 514.5 nm, the F/R shows a log increase with age. Older lenses, above 60 years of age, excited at 647.1 nm give a steeply rising sigmoid curve. In developing this procedure, the authors found that for each lens there is a characteristic wavelength that is called the critical wavelength (lambda critical). At wavelengths longer than lambda critical the Raman signal appears in the absence of a broad fluorescence peak; at shorter wavelengths the fluorescence intensity increases enough to overwhelm the Raman signal. For normal lenses, clear and not heavily pigmented, the lambda critical is age dependent, giving a curve that is a flattened sigmoid approximating a straight line.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002386:Cataract / Q000175:diagnosis; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007834:Lasers; D007905:Lens Diseases / Q000175:diagnosis*; D007908:Lens, Crystalline; D008297:Male; D008875:Middle Aged; D013050:Spectrometry, Fluorescence; D013059:Spectrum Analysis, Raman