Reliability of photometric measurements in the Zeiss fundus camera

The authors test the hypothesis of systematic errors in photometric and/or densitometric measurements performed by Fundus camera equipment. By means of 2 different methods (reflection and transmission) the non-uniformity of light-distribution on sample surfaces placed in front of the fundus camera is shown. The consequent point by point variability in retinal illumination can be defined as the 'retinal shading problem'. This conclusion must be taken into account when equidensitometric measurements are carried out on eye fundus images with fundus camera, by photographic, cinematographic or TV techniques.