He was also known for his research on vision and the chemical changes occurring in the retina under the influence of light. Using the "visual purple" (or rhodopsin), described by Franz Christian Boll in 1876, he attempted to make the basis of a photochemical theory of vision, but though he was able to establish its importance in connection with vision in light of low intensity, its absence from the retinal area of most distinct vision detracted from the completeness of the theory and precluded its general acceptance. Kühne also pioneered the process of optography, the generation of an image from the retina of a rabbit by applying a chemical process to fix the state of the rhodopsin in the eye. Later, Kühne attempted his technique on the eye of a convicted murderer from Bruchsal, Germany with inconclusive results.