Rethinking the Process of Vision

I have been asked by a number of correspondents why I have not written contrasting my explanation for retinal light interaction with traditional models. So…forthwith…

Traditionally in the science of vision it is assumed that photons interact with pigment molecules in the outer segments of the cone and rod retinal receptors. Each receptor is assumed to contain within it different pigments that result in the detection of different wavelengths or (incorrectly)‘colors’. No function is ascribed to the matter (and distance) between receptors. The retina is simply an array of receptors each assumed to be individually sensing light with these signals somehow (never explained) assembled into the visual image. The outer segments of receptors where all agree light interacts are of extraordinary length – about 50 microns. The reasoning used to explain this length is that this mass is necessary to “increase the probability that photons will be absorbed”. This is termed the “photon catch” hypothesis.

From this point on it is explained that the larger cone receptors (99.9% of which are contained within the small central foveal region of the retina) somehow share in detection of the three primary “colors” in essence, envisioning that there are three different types of cones – “red sensitive” etc.. The far more numerous smaller rod receptors that surround the fovea, and that occupy the bulk of the retinal surface, are said to be involved in detection of what is termed “black and white” and/or “low level” lighting conditions.

It is amazing that how such a retina acquires and processes the final colored spatial image of vision is never addressed. The idea of the three types of cones leads directly to the belief that it is assumed that the retina is located at the “image plane” of the optical arrangement of the eye. This is the plane in a camera where photographic film is located. If this were the fact there would necessarily be some logic to the spatial arrangement of (let’s just stick to) the “color sensing” cone receptors of the fovea. Assuming this model, they would have to be arranged in some kind of spatial order, i.e, as tiny RGB (primary color) sensing “triads” or logical “strip” configuration of the image sensing silicon chip of a digital camera. Some sort of spatial order would be necessary if the retina were the image plane of the eye.

But, even if one assumes that red, green and blue sensing (or “classes”of) cones exist (which in fact they do not!) they are not even then arranged in any such ordered fashion! And further, even if one makes this erroneous assumption, and attempts to see cones of differing wavelength sensitivity, they find that such cones are arranged randomly – with a further problem that the blue sensing variety are hardly in evidence at all. See, for example, Roorda & Williams remembering that in this work “pseudo colors” are used to identify the response of cones. Such use of colors does not at all correspond to the direct response of cones but rather what the authors believe that response to be.

All of this is very strange and one comes to the conclusion that, after assuming an incorrect model a long time ago, the field has been attempting to fit (or “stuff”) subsequent data into it where, using even elemental logic, such data does not fit! I have pointed out a great deal of this problem in my work with perhaps the work of the Nobelist George Wald first coming to mind. See my discussion of George Wald’s work ( see Wald) where it seems glaringly obvious that his experimental results agree more with my explanation of the vision process than with traditional thought. Wald noted that the all-cone fovea was “blue blind”, i.e., that it contains none of the ephemeral “blue-sensitive” cones posited by vision science. This experimental result of Wald seems to have been disregarded although it is in complete agreement with my explanation. One should pay particular attention to my discussion of Wald’s Nobel Lecture where more of his thinking seems to substantiate my concept.

Another example of “results that don’t fit” that comes to mind is the completely incorrect dichroic orientation of the rhodopsin light–accepting complexes within the light-interactive retinal outer segments noted above. These molecular complexes form the light energy-accepting sites within receptors. The dichroism of such chromophoric molecular complexes defines the preferred direction for accepting light. It has long been established (I provide references) that these complexes in retinal receptors are oriented to accept light from the side, i.e., orthogonal to the direction of incident light. This is in complete agreement with my explanation for light interaction and is completely at odds with the traditional view described above that “photons interact…” and that the function of the lengthy stack of rhodopsin complexes forming the receptor is to increase the probability of “catching” one! This long understood point seems to have been completely disregarded!

There are numerous other modern results that are not in agreement with traditional thoughts of light interaction. Perhaps a major one… new results by Boston University (referenced in the body of the work) demonstrating that when the diameter of a fiberoptic lightguide is reduced to sub-optical wavelength dimensions (less than one micron) light is transmitted around and not through the guide. The smaller the diameter the more light is shifted outside of the body of the fiber. This is the case for retinal receptors and is in agreement with my explanation. The finding also renders moot the considerable body of work in the vision field that has modeled receptors as lightguides with traditional thought that light is transmitted within the guide. It is this type of thought that has reinforced the erroneous idea of “photon catch” mentioned above!

I could go on noting other vision data “that doesn’t fit”, and I do in the body of the work, but it is time to move on.

My explanation of light interaction with the retina posits that the fundamental interaction involves light interacting as the wave of classical physics in the inter-receptor spaces, i.e. the spaces between adjacent cones and rods. The receptors themselves, and specifically the retinal molecules contained within them, form what in physics are termed “quantum confined electron” spaces. One should read further into the work as I have repeatedly discussed this interaction.
When one sees this it becomes obvious that the retina forms a logically arrayed diffraction surface, which, in turn, defines this surface as the Fourier plane of the optics of the eye. That this might be the case had been guessed at by a number of investigators but it is now demonstrated. It becomes immediately apparent that the retina is not the “image plane analogue of photographic film” that vision science has tacitly assumed (discussed above) but that, what had previously been thought of as an aberration (“chromatic aberration”), forms the fundamental image-forming light interaction of vision!

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I THINK IMPORTANT:

Following from the above, I enjoy very much the idea that this forms the basis for the thought that the eye evolved directly as the physical embodiment of the well understood physics principles for the diffraction of light. Combined with the equally well understood principles of self-organized molecular lipid bilayers, one can visualize formation of the primordial eye – as the result of light shining through a drop of water? One more physical result must be invoked to couple the wavelength of light with, and to form, a lateral structure ordered to detect these wavelengths (for a description of this effect see Dworschak referenced on my web site under the heading “A Brief History”). GEOMETRY THEN ENTERS. The simplest way such that a lateral structure could be organized (or “coded”) would be to employ the fundamental principle of this work, namely. that “an admixture of the smallest number of differentiable regions (two) yields three lengths”.(see the “Rosetta Stone” diagram on my web page). THIS IS THE GENESIS OF THE TRICHROMICITY OF VISION. There is no basis for “design” in this progression.

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There is a great deal that follows from this understanding not the least of which is an understanding that Edwin Land’s theory and color vision experiments are completely verified. The retina that I define makes clear that bands of the intensities of the three primary wavelengths are used to synthesize the sensation of the “hues of color” and , importantly, defines the existence of a geometrically determined location where exact mid-band (550 nanometers) wavelengths interact on the retinal surface in exact accord with Land’s prediction.

A second major finding of this new model is the first explanation for the long known, but never explained, result that the biological retina is able to detect at the quantum single photon level (in light of the above I would prefer to use the term “quantized interaction”). I have written about this in the body of the work but, in summary, it for the first time provides a logical route to an understanding of the connection between the regime of quantum physics and biological system such as vision. In short, I believe that if one wants to progress in understanding the vision process study quantum physics!

I’ll not go on with this here as one can read the body of the work.

GCH

1/26/08

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This entry was posted on Friday, January 25th, 2008 at 10:48 am and is filed under Running Commentary . 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.