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We have developed a new lens measurement system (LMS) that simultaneously measures the intensities of fluorescence and Rayleigh components at various distances into the lens along the optical axis. The noninvasive measurement is performed through an undilated pupil, and with the assistance of a pupil tracking system that facilitates maintaining the x and y positions of the sample volume (ca. 300 mm in length, 600 mm high, and 80 mm wide) to within 6100 mm of any programmed "lock" position. The intensity of the Rayleigh component that is used to normalize the measured fluorescent signal serves to correct the attenuation effects due to absorption and lens light scatter (Mie–Tyndall type). This report, resulting from a SpectRx Site L clinical study using a refined instrumentation (SpecRx Scan V), presents analysis of fluorescence and Rayleigh data from the lenses of 923 controls and 239 diabetic subjects (45 Type I and 194 Type II) ranging from 23 to 75 years old. Fluorescence and Rayleigh data have been obtained via confocal mode from various locations nominally along the lens optical axis (the true trajectory of a sample volume could be shown in a figure) for controls and diabetics, at different ages, using three pairs of excitation and collection wavelengths: 364/495 nm, 434/495 nm, and 485/515 nm. For control subjects, there exists a strong, almost linear relationship between age and fluorescence, while diabetic subjects tend to deviate from this age fluorescence relationship. Our data show that the lenses of diabetic patients are subject to an accelerated aging process, presumably due to an elevated level of brown and fluorescent protein adducts and crosslinks from nonenzymatic glycosylation (Maillard-Amadori reactions). We have also shown that by using the measured Rayleigh profiles to normalize the measured fluorescence, most of the absorption effects are removed and therefore the separation between the fluorescence of diabetics and controls is greatly improved.
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