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Eckhard H. Roth; Ocular Spontanous Photon Emissions in Humans. Invest. Ophthalmol. Vis. Sci. 2012;53(14):742.
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Otoacoustical Emissions are known for decades as a tool to enhance the performance of the ear when the signals that are to be noticed are within very low amplitude levels. Platon in "Body and Sences" postulates some "matter like light" that leaves the eye during the visual process. This investigation was done to check whether or not there is such a thing like Photoemission of the retina.
A photo-sealed room was built and monitored that in fact no light particle form the outside could enter or secondary photon-effects like fluorescence were present. A photomultiplier (PM) was positioned in front of a pupil-dilated eye of a normal subject. The color sensitivity of the PM was similar to that of a human eye. The picked up signals of the PM were recorded and converted to acoustical signals like in a Geiger-Mueller counter.
Photosignals are easy to be picked up by this simple experimental set-up. Photo-noice is produced by the receptors of the retina. Like a lock-in amplifier in electronics the receptors establish a dark-current. The head of the subject has to be positioned carefully like in a slit-lamp examination. The frequency of the random signals at the PM are significantly higher in dark adapted eyes than in light adaped.
The biochemical pathway of Rhodopsin works in both directions. Rods and Cones produce different numbers of photons related to their activity. Further investigations with more sophisticated optics and photo-electronics have to be done to locate on the retina the exact spots where the photons are emitted.
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