Upon his retirement from that post, he became professor of ophthalmology and visual science at Yale University until 1977. Even then, however, retirement was only nominal, and he remained active in the field of visual physiology until last year.
Tomita's early research focused on the physiology of hearing and not on visual physiology. His work was frustrated by the Second World War, which kept members of the international scientific community isolated from each other. Because recognition of his work did not come until after this period in his life, he once said 'People often ask me what on earth I did before I reached the age of 40'. During this time he greatly enjoyed solving technical problems and the challenges of getting nature to reveal her secrets. Tomita's interest turned to vision research after he read the book Sensory Mecha- nisms of the Retina by Ragnar Granit in 1947.
Tsuneo Tomita's many contributions to visual physiology included discovering some of the fundamental mechanisms involved in the activation of photoreceptors and the subsequent processing of sensory information. His starting point was the analysis of the electroretinogram by means of intraretinal microelectrodes. His most crucial discovery was that the vertebrate photoreceptors, rods and cones, respond to light stimulation with hyperpolarization. This unexpected finding challenged and changed the belief that all sensory cells depolarize upon stimulation. Tomita then found that the spectral sensitivity curves measured by recording the receptor potentials of cones closely matched the absorption curves of their photopig-