[Multisubstance analysis. Detection of changes in the optical density in individual layers of the optic fundus]

A promising method for noninvasive objective diagnosis and monitoring of the course of a therapy is spectrometric investigation of the human ocular fundus. Application of this method in clinical practice depends on the development of suitable procedures for deconvolution of the measured spectra. The availability of microcomputers permits the performance of complicated calculations directly at the measuring device. Based on the two-photon flux theory, the influence of absorption and scattering in anatomically determined layers of the fundus will be considered. For this reason, an iterative principle for radiation transport into the fundus is introduced, allowing derivation of a physical model for calculation of the spectral course of the reflected light. In the multisubstance analysis a measured spectrum is approximated by the model function. During this analysis the optical densities of photosensitive and nonphotosensitive pigments and the reflection at intermediate layers can be calculated. As an example of multisubstance analysis, the deconvolution of foveal reflection spectra of normals and type I diabetics is demonstrated. This method makes it possible to show that early diabetic alternations occur in the choroid.