Imaging spectroscopy of the human ocular fundus in vivo

Spectroscopic measurement of light that is reflected from biological tissue in vivo is being investigated for various clinical applications. One special object of investigation using optical methods is the human ocular fundus. A fundus reflectometer that enables the simultaneous acquisition of up to 192 spectra arranged in a horizontal line across the fundus is described. The underlying optical principle of the device is the confocal imaging of an illuminated narrow, slitlike field at the fundus to the entrance slit of a spectrograph. This is imaged by the grating of the spectrograph onto a two-dimensional CCD chip that records the local distribution of ocular fundus reflectance spectra within a wavelength range of 400 up to 710 nm with a resolution better than 2 nm and a local resolution of 23 mm in a field dimension of 1.5 mm. The performance of the device was investigated, the effects of confocal and nonconfocal imaging are discussed, and some representative measurements are presented.