Rethinking the Process of Vision

My explanation for light interaction with the retina is that, in contrast with traditional thought, what are actually encoded on this surface are the wavelengths of light that correspond to the longitudinal chromatic aberration (WIKI) of the lens of the eye. Rather than being termed an “aberration” this diffractive wavelength discrimination effect lies at the very core of the vision process. That the retina is so structured shows clearly that the  the eye – and the resulting vision process –  represent nothing more than a physical embodiment of the well understood physical principles for the diffraction of light.

The retinal surface that evolved to encode these wavelengths can be seen to have been formed using the increasingly understood principles of molecular self-organization. As we enter the era of nanotechnology our knowledge in this field is increasing rapidly. It is fascinating to note that perhaps a seminal experiment in this field was performed by Franklin (the Ben of our founding fathers!) who, intrigued with the spreading of oil films on water surfaces, deduced in the 1700’s the dimensions (unimaginable at the time) of single molecules. We now understand that the basis for this effect is the polarization of oil molecules relative to a water surface causing then to order themselves into monolayers and “self-spread” on the water surface. We now understand a great deal more about these molecular self-ordering effects with perhaps the most important being the nature of polar long chain lipid molecules to form bi-layers that are the ubiquitous membrane of living cells.

There is one more physical phenomenon that must be invoked to illustrate how light shining through that drop of water (the primordial lens of the eye?) formed a lateral molecular structure that spatially encoded different wavelengths of sunlight. Such an effect indeed exists. For a description of this effect see “A Brief History” and the experiments of a number of groups (Dworschak, Young and Siegrist) where the wavelength of a beam of light that is orthogonally incident on a surface is reflected laterally (at right angles, i.e., in the plane of the surface) to form physical structures (optical “gratings”) that have a period that corresponds exactly to the incident wavelength. I propose that this resulting wavelength pattern is “scaffold” to which the self-organizing molecular layers described above conformed.

And then..to get ahead a bit.. nature, as described below, used an elegantly simple geometric scheme to encode the wavelengths of light. It becomes abundantly clear that the eye is not a camera-like “complex design” that both vision science (!) and creationists want to believe.

* I do not want to digress here but it is important to note that the pattern of wavelength detected on the retina that has been chromatically diffracted by the lens of the eye absolutely defines the retina as the Fourier plane of the optics of the eye. The retina then is not the “intensity-only sensitive” image plane that has for so long been erroneously assumed. This has major consequences to understanding the vision process, color perception etc. as I note in the body of the paper

Proceeding to thought about the mechanisms used by the retina to process detected wavelength signals, it is tempting to envision the retina behaving as the analogue of the spectrometer that we commonly use in the laboratory to analyze the composition of light. These devices using prisms, motors etc. possess the capability to decompose a spectrum of light into its constituent wavelengths. Vision science has believed that the retina somehow acts in this manner and then proceeds, again incorrectly, to propose that the initial wavelength detection process leads directly to the sensation of “color”. In attempting to translate the idea of such a “laboratory capability” to the biological realm the concept of pigment molecules contained within retinal receptors has been invoked. This has led to more incorrect notions such as the idea that “classes” of cones exist that are sensitive to the different “colors” even though a great deal of experimental evidence has been accumulated that denies this assertion. When viewed from the perspective of my explanation this seems shallow and irrational reasoning but this has been the thought process in vision science for a hundred years!

But, nature does none of this using a far simpler and elegant geometrical nanostructural construction to form the visual image as I will proceed to explain!

Corroboration of my ideas comes from an unexpected source music theory generating the following text (emphasis is mine):

.”….colour is a matter of relative geometry and not “absolute” chemistry. Land`s discovery was that our brains self-organise to the available wavelengths around a median point - (the “fulcrum”). Further, the same photoreceptor geometries seem to emerge in plants.”

I must pause here to re-introduce the Einstein quote I have used before: “ALL IS GEOMETRY”.

But to set the stage, let’s talk again for a moment about the mechanism for the interaction of light that I described above. This will, perhaps, put this concept in a better prospective for the following discussion. The retina, when viewed from above, is seen to be composed of an array of concentrically arranged light detection centers. These centers can be considered as individual “optical antennas”, that, with the caveat that a quantized region is involved, are loosely analogous to the dipole antennas that we familiarly use in longer wavelength regions of the electromagnetic spectrum. As described above, each center in this nanostructural construction involves a wavelength defining space of variable dimension that is adjacent to a “quantum confined” electron space (or spaces) that are of fixed dimension. One can then go on to envision the retina abstractly as an array of circular spaces of two sizes – t he cones and rods of which we are familiar. I must note that this visualization comprises the entirety of the retinal area containing both the receptor bodies themselves and the inter-receptor medium.

Now the key point – why did nature evolve two sizes (or diameters) of retinal receptors? It can be seen simply that an admixed array of two sizes of circles (as our abstract retina) leads geometrically to three dimensional possibilities. See the “Rosetta Stone” diagram that I have used to express this point.

Rosetta Stone Diagram

Then, fundamental to light detection in the eye, if geometrical lengths correspond to specific optical wavelengths detected as I propose, the retina detects, or is “narrowly tuned to”, three and only three wavelengths. I would propose that this provides the explanation for the finding by Young that the vision process is trichromatic.

These three discrete wavelengths detected by the retina have been historically termed the “primary colors”. I believe that they are in fact primary but not yet “colors” reserving that term for the product of the synthesis that the retina (or visual cortex of the brain) performs combining these three primaries into the many hues that we term colors. This would eliminate a great deal of confusion in vision science!

The specific array of receptors on the retinal surface (the historic 1935 data of Osterberg) shows that these three primary wavelengths are detected in circular bands concentrically surrounding the central fovea. Further, it is seen in this explanation that these bands are composed of a variation in density of these primary wavelength detection centers. The wavelength of the interaction has already been determined by diffraction in the eye! Such a density of centers must correlate with the intensity of detected light. Thus, it is the intensity of each primary wavelength that is positionally encoded in the bands on the retinal surface.

As shown in the body of the paper Huth, the all-cone fovea encodes the highest intensity of the “red” primary, the concentric band centered at 7-8 degrees of retinal angle the highest intensity of the “green” primary, and beyond 20 degrees, the highest intensity of the “blue” primary. Nature uses a synthesis of these three intensities of primary wavelengths to arrive at what we see as the many hues of color!

Perhaps the most fundamental result of this explanation is that this geometric coding of “admixture of two sizes” results in an exact central wavelength being geometrically defined on the retinal surface. This would correspond to the 550 nanometer central wavelength of the visible band and is defined by the cone-to-rod dimensionality. The identification of such a fixed wavelength reference on the retinal surface would seem logically to be necessary in any subsequent operation to synthesize color. It is fascinating that Edwin Land in his color experiments deduced the presence on the retina of such a fixed reference! He termed it the “fulcrum” point.

This geometric explanation reveals a number of other avenues to our increased understanding of the vision process. The unique ratio of the two sizes of cone and rod retinal receptors is 1.8:1 and this corresponds to the visual bandwidth (700-400 nanometers). This, in turn, results in the “eight-around-one” octagonal motif of rods-around-cones at 7-8 degrees on the retinal surface. This same octagonal motif is present in the visual organs of many species! Why? All is geometry!

Thus it can be seen in this progression of ideas that there is no basis for “design”, intelligent or otherwise, in the eye and vision. The eye very simply objectifies the laws of physics (the diffraction of light) and basic geometry. There are still many mysterious aspects to the vision process and these reside in the still largely unknown realm of what constitutes quantum reality. The key here is an explanation for the heretofore unresolved ofthe eye and vision to detect single quanta. Even here this explanation provides clues as to how this comes about. As I have written, I believe that the dividing line between the biological system and the quantum realm is located at the retinal surface! Again, see Huth

In short, I feel that to make progress in the study of vision study quantum physics!

GCH

2/4/08

This entry was posted on Sunday, January 27th, 2008 at 12:26 pm 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.