Spectrophotometer for noninvasive measurement of intrinsic fluorescence and reflectance of the ocular fundus

Abstract

A spectrophotometer for noninvasively measuring the intrinsic fluorescence and the reflectance of the ocular fundus is described. The instrument uses multichannel spectral analysis for recording fluorescence emission spectra (500-800 nm) with seven excitation wavelengths between 430 and 550 nm and for the determination of fundus reflectance spectra (400-800 nm). Measurements are performed from a discrete fundus area, with a spatial resolution of a 1-2° visual angle. Calibration procedures are detailed. Representative fluorescence and reflectance spectra obtained from five normal subjects indicate that the fluorescence originates from within the fundus layers. Although the absolute fundus fluorescence measurement is affected by lens absorption and ocular refraction, it is minimally influenced by the strong fluorescence of the crystalline lens.