On Retinal Pigments
January 12th, 2006 | No Comments »The accepted view of the physics of light interaction within the eye is that photons interact with different pigment molecules contained within the cone and rod receptors of the retina and that this forms the basis for trichromatic vision, and, in effect, explains everything. I have proposed an alternative mechanism for this light interaction that seems at first glance to be at variance with this photon/pigment hypothesis. Specifically, I propose that the overall geometric nanostructure of retinal organization, that when viewed from our emerging knowledge of “optical antenna structures”, explains at once the trichromicity of vision and provides a logical explanation as to how the visual image is acquired – in the Fourier domain. Other vision results are explained including the evolution of the specific organization of retinal receptors, George Wald’s finding of the “blue blind” fovea, and, the color vision experiments and theory of Edwin Land. Although the concept posits that light interacts on the retina as a classical wave, the quantum nature of the interaction is preserved in concluding that the absorbing mass- the electron - is contained within the quantum confinement dimension.
I am continually being challenged to the point that “the photon/pigment hypothesis explains everything…….so how can you be correct?”. I will provide a short answer here with longer more detailed arguments presented shortly.
I am reviewing a number of papers suggested to me focusing on the identification, and even genetic manipulation, of these retinal pigments. My comments here focus on thoughts gleaned from a review paper by Nathen that pretty well summarizes the pigment view: (“The Evolution and Physiology of Human Color Vision: Insights from Molecular Genetic Studies of Visual Pigments”, Neuron, Vol.24, 299-312, October 1999).
In summary: I proposed in the body of this work that the retina should actually be considered, in overview, as an “array of structural receptor/”nanowires” with three different interreceptor spacings that result from an admixture of two different receptor sizes – the cones and rods”. I went only as far as proposing that these nanowires were generic, i.e., energy absorbing pigments in both cone and rod receptors possessing the same energy absorption character. In retrospect this should not be the case. Energy absorbing pigments (i.e., retinal plus an opsin component) contained within the bilipid membrane of the thylakoid disks of each type of receptor would undoubtedly have different structural configurations required by the differing dimensional spacings of the cone-cone, cone-rod, and rod-rod appositions. I would think therefore that the small differences (always strangely only a few nanometers centered around mid-band)) that have been observed in the response of retinal pigments represents a structural response to these spatially determined, energy absorption requirements. The measured responses of these retinal pigment molecules are obviously very real but they do not represent the fundamental light absorbing mechanism of the retina.
TO BE CONTINUED
GCH
