Twin-prism stereo-separator

We describe a twin-prism stereoseparator for the Zeiss fundus camera which gives high-quality stereophotographs of the optic disc and simultaneously records both images on the same frame of film. The stereobase of photographs taken with this system ranges from 2.0 to 4.5 mm. It varies linearly with the entrance pupil which ranges from 4.0 to 6.5 mm. The instrument provides a reliable method for monitoring changes in optic disc topography.