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

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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 A diagram summarizing my explanation for light interaction with retinal receptors. One sees to the left  the interaction of light as the wave of classical physics adjacent to the side wall of an individual receptor (either cone or rod). It is the dimensions of this space between individual receptors that geometrically defines the wavelength of the interaction. Absorbed light energy is then transduced, in the direction orthognal to the direction of light incidence,  through the bilipid membrane  that forms the thylakoid disk structure (there are many of these disks “coin stacked” forming the length of the receptor outer segment). This represents the point where the electromagnetic energy of light (”speed of light”) is converted to phononic (i.e., mass associated , “speed of sound”) energy. I believe that this latter transport mechanism actually involves “coherent phonons” or  solitons with this quantized vibration being lossless. The intercalation of cholesterol into the bilipid  biological membrane structure implies the existence of solitonic transport. This laterally transduced energy then reaches the rhodopsin complexes contained within the thylakoid disk structure resulting in the isomeric transition of the retinal molecule and generating the electronic signal used in the image-forming process of vision. This complex forms the “quantized electron” space of the light interaction process. The role of the variably dimensioned,  retinal-enclosing, opsin protein is as a “spacing element” to fit the signal  generating retinal into the wavelength-determining ,variable dimensions of the retinal surface (cone-to-cone, cone-to-rod, etc.). In short, “the retinal molecule  is constant with the dimensions of the opsin molecule being variable”.  The reason for the lengthy “stack” of individual thylakoid disks that form the outer segment is to encode a directional signal for use in the image forming process  probably via a “giant electrical dipole” mechanism as I propose.

As we enter the era of defining and understanding nanostructures,  light interaction with the retina of the eye can be seen in the purely spatial and temporal terms of physics.

Spatially, light interacts as the wave of classical physics in the sub-optical wavelength spaces between adjacent retinal receptors and immediately adjacent to the far smaller quantum spatial regime of the confined electron wave.  This latter region represents the ‘absorbing mass’. The wave nature of light implies ‘antenna’ behavior and it is the spatial antenna dimensionality of the inter-receptor spaces (generally the distance between adjacent electron quantum confinement centers) that defines the wavelength absorbed at a specific site. The overall nanostructural interaction can then be seen in terms of either classical and quantum physics. From the quantum view, rather than imagining that a photon is involved one might more properly describe the interaction in more general terms as “quantized”.

Temporally, as defined in this work, light interaction and the fundamental basis of the vision process must occur in the very fast time regime – times of the order of 10^-15 seconds (femtoseconds) or less. Considering the temporal reduction of signal-obscuring electronic noise as I propose is the only way to explain the extraordinary  ability of  vision to detect and process the signal from single photon (or quantized) interactions. Additionally, this proposal is in consonance with the measured isomerization time of the retinal molecule within receptors that has been shown to occur on this time scale.

Going forward, any understanding of the vision process therefore will encompass the sub-optical wavelength spatial and very fast quantum time domains. This defines the realm of quantum physics and any real understanding of vision will involve, and always has involved, this discipline. Further, I believe that such study will lead to a new and fundamental understanding of brain function. The brain functions on the principles of quantum physics.

All of the above is in contrast to traditional thinking where light has been thought to interact within the cones and rods themselves leading to such historic misunderstanding as the dogmatic statements that  “cones detect color”,  “rods detect black and white”, the “photon catch” hypothesis etc. none of which is consistent with the long accepted organization of retinal receptors.

It can now be seen that the receptors themselves are merely spatially-defining molecular assemblages and that the retina is organized as a geometrically-defined spatial construction. Three spaces (or inter receptor dimensionalities) are uniquely specified that define the three primary wavelengths detected by the retina that have been historically characterized as the “three primary colors” (the hues of color are determined by a blending of these three primaries in the same way that this is accomplished technologically). The retina as I have said so often does not detect “color”

GCH

1/8/08

On the subject of a predictive experiment that could be performed that would validate (or invalidate) my explanation.

I have proposed such an experiment on a number of occasions to the Roorda group at Berkeley (last on April 3, 2007) and will repeat that request here:

“I repeat my proposal that measurement of the wavelength sensitivity of ‘retinal mosaics’, made by Rooda & Williams (Nature, Vol.397, pp 520-522, 11 February 1999) at a retinal eccentricity of one degree, be made at larger retinal angles. I predict that such measurements will show an increasing density of green ‘cones’ with increasing retinal eccentricity reaching a maximum density (i.e., total green response) at  7-8 degrees. These green sensitive centers will not (could not because there are very few cones here) correspond to cone response but rather to cone-rod appositions which reach a maximum at that point”

GCH

1/5/08

I have been away thinking about other things. But here is a thought about vision that might benefit from an update:

1.) I have described previously what the fundamental light detection centers (or “devices”) of the retina must consist of. My diagram below shows how light as a wave interacts in the inter-receptor space between two adjacent ( i.e., traditional rod or cone) receptors. To be more precise, the distance I refer to is between adjacent quantum confined electron centers. This space may include the inter-receptor fluid medium and the lipid structure of the receptor thylakoid membrane that leads to the retinal/rhodopsin electron confinement center. In overview the situation can be viewed in pure geometrical terms – but I will leave that for now. Each“device” then possesses the ability to detect light intensity and direction (see diagram). These are the requirements of “Fourier plane detector” as this explanation of the vision process requires.

Following the accepted result that the retina is able to detect single quanta (photons), I have proposed how this is accomplished by this structure. First, it must be understood that the lateral dimension (i.e., in the plane of the retina) of each device is of sub-optical wavelength (less than 0.5 micron). This corresponds to a light detection center density of many millions of these centers per square centimeter! It becomes clear the electronic characteristics of a device of this size (capacitance etc.) in conjunction with the realization that unwanted electronic “noise” is a time related function (see Huth) leads to the conclusion that the single quantum detection event is taking place in very fast time scale (probably femtosecond or 10^-15 sec) and explains how this biological system accomplishes this feat at body temperature! All of this is more fully discussed in the body of the text.