Rethinking the Process of Vision

In overview, I have been content in the original draft of this paper directed to the vision science field to characterize the fundamental interaction of visible light with retinal receptors as a “new type of optical antenna” wherein the regimes of classical (wave) physics and quantum theory exist “side-by-side” in the nanodomain. The organization of cone and rod receptors on the retinal surface and the refractive properties of the structures of the eye lead inescapably to the conclusion that the eye evolved to detect light as a wave in interreceptor spaces immediately adjacent or between individual receptors. The receptors themselves act as “quantum confined” electron spaces. All receptors both cone and rod have this singular and identical function. It is the geometrical spacing of receptors that dictates where on the retinal surface different wavelengths are absorbed. This logically explains the unusual distribution of cone and rods and clears up a great number of conundrums that have existed in the vision field (such as the non-existence of “blue sensitive” cones).

I felt that delving too far into the physics of the light interaction would confuse the main message that was intended to be the geometrical simplicity of the concept, i.e., the “rosetta stone” of three geometric lengths underlying the trichromicity of vision. It was necessary to introduce physics, however, as in defining a giant dipole mechanism to explain light directionality necessary to satisfy the Fourier equation (that the premise proves is the fundamental basis for the vison process).

With the recent news connecting evanescent wave phenomenon with light guides having dimensions smaller than light wavelength prods me to discuss this relative to my concept. To begin, this situation exactly reflects the light interaction geometry that I have proposed for the retina. One can certainly look at it this way, i.e,. that the sub-micron dimension of the receptor (or at least it’s central core) “forces” the light to interact in the spaces adjacent to the receptor. Light as wave then travels down the “long tunnel” (50 microns in length) between receptors “beating against”, while along the way imparting energy to, individual rhodopsin complexes contained in the lateral membrane of stacked thylakoid disks. I did note in the body of the text that directionality of light would alter the total of energy deposited in adjacent receptors but did not address the physics mechanism involved.

I propose that this mechanism is based on an evanescent wave (EW) directed at right angles to the direction of light reflected down the interreceptor space. Such waves have all of the necessary characteristics to effect this interaction. The EW is absorbed exponentially in the absorber and as demonstrated in the relatively new field of Evanescent Wave Spectroscopy actually has the specificity for detecting single molecules and even atoms. Light energy is then imparted to the rhodopsin molecular complexes that are arranged in the membrane of the thylakoid disks that form the body of the receptor. It has even long been demonstrated that rhodopsin complexes are aligned within membrane dichroically, i.e., to accept light from this direction (which has always been strange and unexplainable!) The following figure diagrams this interaction.

Also explainable is the seemingly random arrangement of rhodopsin within the lateral surface of the thylakoid disks. This would seem to be to effect a non-directional amplification mechanism for light entering from differing directions (the “giant diple”).

I beleive as proposed in the text of the complete paper that energy is transferred laterally (from the evanescent wave) via a lossless solitonic mechanism. I think that this would be crucial in the overall biological vision process.

I apologize for the brevity of this link - I will work on it further as I get time.

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ADDED 3/30/04

I will copy a paragraph from POLARISATION PHYSIOLOGICAL OPTICS by N.D. Zhevandrov (Physics Uspekhi, 38. (10).1147-1167, 1995) because it expresses the above thoughts so well ..and,in fact, supports the geometrical light interaction concept.

From page 1165,

“The rod outer segment in vertebrates is essentially a stack of disk membranes, i.e., lipid matrices, containing rhodopsin, a light sensitive pigment. Rhodopsin molecules are globular proteins partly embedded in a double lipoid layer of the membrane. Interaction between hydrophilic and hydrophobic forces results in the orientation of the oscillator of absorption almost parallel to the membrane surface. The membrane is a fluid substance with the viscosity of olive oil. Rotational diffusion of rhodopsin molecules normally occurs in the plane of the membrane which results in chaotic orientation of oscillators in the membrane plane. Therefore, rhodopsin molecules do not exhibit dichroism when the light travels parallel to the axis of the outer segment, as under normal physiological conditions. In contrast, marked dichroism of the rod outer segment is readily apparent if it is illuminated by the light from a laterally posed source, because only the electric vector of the light parallel to the membrane plane can be absorbed in this case.“

This entry was posted on Tuesday, March 30th, 2004 at 12:05 am and is filed under Further Essays, Rods and Cones . You can follow any responses to this entry through the RSS 2.0 feed. You can leave a comment, or trackback from your own site.