Rethinking the Process of Vision

The finding of a direct relationship between geometry and light wavelength on the retinal surface may be the most fundamental insight of this work. It is seen that the exact center, i.e., ~550 nanometers, is geometrically defined at a retinal eccentricity of approximately seven degrees. This degree of retinal angle then becomes a fixed wavelength reference from which all other wavelengths can be compared in the vision process synthesizing  the hues of color. Edwin Land brilliantly deduced the presence of just such a reference in his comment “…we have learned that the eye must have a fantastic mechanism for finding a balance point within a band of wavelengths”. It seems clear that the presence of such a fixed reference provides an answer to the longstanding conundrum of the unique “color constancy” of vision - again, as Land proposed. We all “see green” because we all have the same sizes of retinal receptors and thus the same geometrically determined color reference!

The eye is then not to be viewed as a kind of  laboratory spectrometer that selects colors from different classes of cones but rather as a result of  evolutionary biology  where the fundamental physical principles of the diffraction of light and geometry are directly related to produce vision!

The following is an historic figure from Pirenne ⁽¹⁾ of a drawing made of this reference point on the retina. Note that this is the first point where octagonal symmetry is present. This is the eccentricity where sufficient rods have been introduced to completely surround each cone and a symmetrical structure results. On either side (i.e., inwards towards the fovea and outwards towards the peripheral retina) rods and cones are statistically distributed that has caused such confusion in the vision field attempting to find some order.

⁽¹⁾ I wish that that readers would review this seminal reference: “VISION AND THE EYE”, M.H. Pirenne, The Pilot Press Ltd., London, 1948

A NOTE REGARDING THE ABOVE FIGURE - I would assert that the figure represents, in the living state, a perfect octagonal symmetry since the ratio of the diameter of cones to rods is an exact ratio (1.8:1) to support that morphology. The microscopic sections that Pirenne must have used to create these drawings (and in the freeze-dried sections used in contemporary electron micrography) had been dried unavoidably introducing spatial distortion. GCH

This line of thought relating geometry and light wavelength leads directly to the processes involved in the evolution of the eye. It is obvious that the eye is the direct geometric materialization of the fundamental physics principles of the diffraction of light. If anyone wants to introduce “design” into this they will have to go back one step further into designing the  fundamental laws of physics!

And further, if one doubts that the basis for this explanation that chromatic aberration of the lens of the eye provides the information used in the vision process,  I will quote again from George Wald’s  “Blue-Blindedness” paper written in 1967 about which I commented  yesterday.

“Any lens made of one material exhibits chromatic aberration; it refracts short wavelength light more strongly than long wavelength light, and hence brings blue light to a shorter focus than red. Color-corrected lenses can of course be made by using two glasses differing in refractive index; but, so far as is known, no animal has yet succeeded in developing a color-corrected lens. Though the cheapest of cameras have color-corrected lenses, the lens system of the human eye – as Newton observed – has no color correction whatever”

Corroborated by this statement, and in the light of my geometric explanation, it is obvious that the eye uses chromatic dispersion (my term) to form the visual image (in the Fourier  frequency domain). This has heretofore been incorrectly, with unfortunate consequences, termed an aberration in the history of vision science!

Issac Newton saw this! Why has it been disregarded in vision science?

GCH

5/31/08

Please read this paper (J. Opt. Soc. Am, Vol.57, No.11, November 1967). The retina described by Wald corresponds almost exactly to the retinal response of my explanation by making the simple substitution of the term“rod-rod appositions” for “blue-sensitive cones”.

Even his opening paragraph:

“In 1894 Konig and Kottgen reported experiments designed to show that the central region of the normal human fovea is blue blind (with reference). Konig had come to believe the sensation of blue is excited by rods…..”

One should also read George Wald’s Nobel Lecture at noting his Figure 15 that defines retinal response very much as I explain.

http://nobelprize.org/nobel_prizes/medicine/laureates/1967/wald-lecture.pdf

At the risk of being accused of taking Wald’s thoughts out of context I will transcribe some sections of his text. I believe that these summarize the thrust of the paper.

From the Abstract (p.1289):

“The blue cone system falls in sensitivity from the border of the photopic zone – the functionally all-cone areas – to a minimum, usually to extinction, at it’s center”…”Also the red – and green cone systems display the opposite gradient; their sensitivities decline regularly from the center toward the borders of the fovea and beyond”

(Wald defines the “photopic zone” as being “dominated by cone vision” and extending to “visual angles of at least 1.5 degrees”. This represents the all-cone fovea where in my explanation cone/cone appositions form the “primary” long wavelength (or “R”) peak and, additionally, precisely define the long wavelength limit (~700 nm) of the visual band.)

The above quote describes the plan of light interaction on the retina as I define. This is undoubtedly the basis for the retinal sensitivity curve that Wald presented in his Nobel lecture (Fig. 15). It is truly beyond me how anyone seeing this, i.e., that color sensitivity is segregated into specific areas or “rings” on the retinal surface did not think to relate this diffractive surface to the wavelength refractive properties of the eye!

From p.1290..My thoughts have been anticipated!

Wald, (after calling it a misconception), quotes:

“Wilmer (1) had thought to explain color vision in terms of only two kinds of cone, or cones, and cone-like rods, the third color mechanism, that for blue, involving the cooperation of ordinary rods Hence, he too expected to find no blue receptors throughout the entire photopic area…”

⁽¹⁾ E.N.Wilmer, Nature 153, 774 (1944), and E.N. Wilmer, J. Theoret. Biol., 1, 141 (1962))

Wald goes on to say that “the photopic area of the retina contains large numbers of such blue-sensitive cones”. This area does contain a (low) density of “blue-sensitive centers”. What I believe that he is actually observing is the statistically small, randomly distributed, density of rod/rod appositions in this critical area (~1.5 degrees) of the retina where rods are just beginning to intrude on a rapidly declining cone density in the retinal morphology.

From p.1294:

“It seems therefore that the absence or near-absence of blue receptor function is characteristic only of the center of the fovea. It is a matter, not primarily of size of field, but of foveal topography”

From p.1296:

“The general gradient of cone concentration in the fovea therefore runs counter to the gradient of blue-cone sensitivity. At the center of the fovea, where cones are most dense, blue-cone sensitivity is minimal, and blue-cones are usually entirely absent. Conversely, at the borders of the photopic area, where the blue-cone sensitivity is highest, the total number of cones has decreased markedly. This opposed distribution is reflected in a converse pattern of relationships that involve the red and green cones”

From p.1298:

“…whereas the sensitivities of the red and green-mechanisms are highest at the center of the fovea, and decline regularly with distance from it, the blue cones show just the opposite gradient of sensitivity, rising from a minimum at the center of the fovea to one half degree to one degree out…”

From p.1299 where Wald recognized the problem of chromatic aberration in the eye:

“Any lens made of one material exhibits chromatic aberration; it refracts short wavelength light more strongly than long wavelength light, and hence brings blue light to a shorter focus than red. Color-corrected lenses can of course be made by using two glasses differing in refractive index; but, so far as is known, no animal has yet succeeded in developing a color-corrected lens. Though the cheapest of cameras have color-corrected lenses, the lens system of the human eye – as Newton observed – has no color correction whatever”

Henceforward , I would propose terming this “chromatic dispersion” instead of considering this effect an aberration

From p.1300:

What we take, therefore, to be normal, trichromic vision is the particular property of an annular zone of the central retina, lying between the blue-blind fixation area and a red-green blind zone some 20-30 degrees out. The special importance of this central zone is that we depend upon it almost exclusively for all phase of photopic vision, and that, all testing of color vision is confined within it, rarely extending more than 2 degrees beyond the fixation point”.

I could not have said it better!

Submitted as revised:

GCH

5/29/08

This work, put very simply, reinterprets the long accepted (i.e., appears in almost every vision textbook!) 1935 retinal morphology data of Osterberg in terms of modern physics and nanotechnology and arrives at an entirely new paradigm for the vision process. An example of vision science being stuck in the past - it was noted for me even within the past week that a contemporary view is that retinal receptors “act as waveguides”. Receptors do act as waveguides, but, in modern terms. When the diameter of such a guide is reduced to the micron and sub-micron dimensions of retinal receptors light travels outside of the guide instead of internally as in larger diameter fiber optic light guides that we now use in the optical communication field (see references in previous comments). This single point validates my explanation for light interaction with the retina! Please…. bring physics, and more precisely quantum and nano technological thought, into vision science!

Any new paradigm, theory, hypothesis etc. must be predictive to be valid. I have sketched out over the history of this work how this new view opens many new lines of thought into the vision and even plant photosynthetic processes and, further, into more esoteric areas of physics and biology. One of these is a provisional linkage of the vision process with the physics of quantum reality in my proposal that an actual physical mechanism exists linking the observer to emerging concepts of an external quantum environment. A physics overview emerges that encompasses the fast time domain characteristic of the quantized interaction of light with the outer segments of the retina and subsequent, slower, biological processes that operate within the human nervous system and brain. These thoughts I believe will ultimately have implications to the conundrum of human consciousness. I will outline in the following a number of these areas here but be clear that this certainly does not constitute a complete or even prioritized listing:

1.) It becomes clear that the eye forms images in the Fourier frequency domain, i.e., that the retina is a diffractive surface that processes both the intensity and phase of incoming light. This opens up many new lines of thought. We have no comparable imaging technology in the visible range of wavelengths to accomplish this. The recent discovery in the solid state of a visible light interactive silicon nanostructure (“porous silicon”) that uses the same light interaction mechanism as the retina provides a starting point for development of a series of new imaging technologies. At this stage of it’s development the technology of porous silicon provides only the high efficiency initial light interaction function and not the comparator (phase decoding) ability of the retina of the eye. It should certainly be possible with development to add the necessary microcircuitry in the sub-porous silicon substrate to replicate this capability.

2.) The diffractive retina explains Edwin Land’s body of experimental work on color vision. It will now be possible with this new understanding, that Land could not have known, to expand our knowledge of how the hues of color are really perceived.

3.) The truly fundamental finding of a geometrically determined reference point at 7-8 degrees of retinal eccentricity that defines the exact center of the visual band! It is nanostructural geometry that determines light wavelength in the vision process. Nothing like this has been seen before. This for the first time provides a logical explanation for the color constancy of the vision process.

4.) The many aspects of fundamental geometry leads to the ability to predict the characteristics of the visual system of any species photosynthetic plant or animal. For example, I have proposed that if two sizes of photosensitive receptors are present in a photosynthetic morphology the bandwidth (as shown in the human retina) will be determined by the ratio of their diameters. The absolute size of the receptors themselves will determine the position of the band of light interaction. I have shown that this seems true for species as varied as fish and insects.

5.) This paradigm predicts that at least two diameters of receptors are necessary to provide the imaging (or sensation) of color. Only an admixture of two sizes can produce the three “primary” wavelength peaks necessary (Land again!) to process the hues of color.

6.) The strange finding that the same octagonal symmetry (rods-around-cones at 7-8 degrees of eccentricity) is characteristic of the retinal morphology of seemingly all species from honeybees to crabs (the references of Snyder et al).

7.) The concept that the eye may not be the passive “camera receiver” that has for so long been assumed, but, may actually radiate a light signal back into the environment. This follows from the fact that antennas – as light interacts with “optical antennas” on the retina – transmit equally well as they receive signals (information). Following this, I have proposed that the well understood principles of optical phase conjugation are involved that would result in the radiation of this signal back along the exact path upon which it entered the eye. This insight leads to a “connectedness” between the observer and the observed that may, in the view of the author, have relevence to the subject of consciousness.

8.) It becomes evident that quantum physics must be introduced structurally into the science of vision. I believe that I demonstrate, for example, that light interaction with retinal outer segments occurs in femtosecond time (there is really a great deal of experimental data corroborating this) and that this forms the basis for the, again understood but never explained, ability of the eye to process single photon (or as I would term “quantized interactions”). It would seem, and has been proposed that information exists and is processed in vision in this (quantum) time domain, i.e, the time domain associated with the frequency of light. I would believe that the “Heisenberg cut” that defines the point of demarcation between quantum and classical physics may occur at the retinal outer segments of the eye. The function of the processes of vision that follow this interaction are, in my view, to “slow down” visual information to the slower time domain of classical physics, or in other words, to human nervous system proportions.

9.) I believe that it is possible to replicate the diffractive pattern of light interaction of the retina on silicon using the above mentioned technological discovery of visible light interactive “porous silicon”. This would be accomplished in experimentation imaging the longitudinal chromatic aberration of the solar spectrum passing through a condensing lens onto a silicon surface while it is undergoing the porous silicon electro-etch process. Such an experiment using the solar spectrum would provide a fundamental demonstration of how a primordial photosensitive organ of vision evolved simply as a physical embodiment of the principles of the diffraction of light and not through any concept of “design”. I believe that this will be a very fundamental experiment and I hope that someone will carry it out.

10.)….and much more……

GCH

5/23/08

As anyone following this work will have noted, I assert that light interacts on the retina in three distinct geometrically defined regions formed by  appositions of the intermixture of cone and rod receptors and not within the receptors themselves. It even becomes possible to view the retina abstractly as a logically ordered array of generic quantum confined electron centers. It may even be helpful to completely do away with the terminology of “cones” and “rods” and view them simply as elements that provide the proper logical “geometric spacing” between the generic (essentially retinal molecule) energy absorbing electron centers.

The three interactions are as follows:

a.) With the hexagonal matrix of cones that form the fovea with this interaction defining the exact long wavelength (“red”) limit of visual response. The fovea is “blue blind” as Wald correctly found!

b.) With the admixture of cones and rods where, at 7-8 degrees of eccentricity, the density of rods is sufficient to completely surround each cone to form a perfect octagonal symmetry. This, again exactly and geometrically, defines the center (“green”) wavelength of the visible band. This geometrically fixed point provides a fixed reference on the retinal surface from which all other wavelengths can be compared in the visual image formation process. This array of octagonal “rods-around-cone” assemblies have been mistakenly termed “M cones”.

c.) With the, again, hexagonal symmetry of the predominantly rod-containing region of the peripheral retina that defines the exact short wavelength limit of visual response.

(I must parenthetically note: 1.) no one as yet seems to have seen my point that the only geometric basis for the octagonal symmetry of the mid band centers is a receptor size ratio (i.e., the diameter of cones to rods) of 1.8:1. This is the only ratio that can result in the octagonal symmetry that is observed and this ratio corresponds to the visible band, i.e., from 700 to 400 nanometers and, 2.) a reminder that the three wavelengths detected as above are “primary” (as deduced early in the history of vision) but are not yet “colors”. The hues of color are determined by comparing these wavelengths in the manner deduced so brilliantly by Edwin Land. Through all of this I am reminded again of the quote attributed to Einstein that “All is Geometry”)

Thus… three narrowly tuned wavelength-receptive regions are defined on the retinal surface.. What is the parameter that varies across each region? At first thought it is the density of receptor sites. But secondly, it is the perfect symmetry of each region that in addition to defining density of sites is related to the point of peak light absorption. One moves from the perfect (large receptor) hexagonal symmetry of the fovea to a perfect octagonal symmetry at 7-8 degrees to a perfect (small receptor) hexagonal, symmetry of the rod containing peripheral retina.

Thus the retina progresses at increasing eccentricity from hexagonal to octagonal to, again hexagonal symmetry.

It is then perfect geometric symmetry that defines the peak of each wavelength absorptionregion.

A diagram from Pirenne that I have previously used showing the perfect octagonal motif at the 7-8 degree retinal eccentricity. I again humbly submit that this is the basis for the “clumping of M cones” that Masuda et al have recently reported (see previous Comments for the reference).

I have not time to go into it here but geometrical perfection combined with the sub-optical wavelength dimensionality of these receptor centers results in a density that precludes overlap of photon (read “quantized”) interactions at each center resulting in the high (nearly perfect) light interaction efficiency in these regions. This in turn leads to an explanation for the ability of vision to detect single photons (or, again, quantized interactions.

GCH

5/21/08

A poster/paper (3832/A375) was presented at the ARVO 2008 Annual Meeting “Arrangement of the Human Trichromatic Cone Mosaic in Peripheral Retina” authored by O. Masuda, H. Hofer, J. Carroll and D.R.Williams. I interpret this work extending the imaging methodology developed by the authors (and previously by Roorda et al) to larger retinal eccentricities, as being in some way a response to my repeated requests that this measurement be made. But….who knows?

I humbly submit that their results seem to verify my projection in their finding of a “clumping” of, what they (erroneously) term L and M “cones” at retinal eccentricities of 10 degrees. They note that this represents the first instance where the packing arrangement of cones is distinguishable from randomness, i.e., that a spatial order is observed. Their exact statement “Previous studies have concluded that the packing arrangement of L and M cones near the center of the human fovea is not distinguishable from random in most eyes”. (does this mean that the packing arrangement in “some” eyes is not random? – please supply a reference?).

I believe that the basis for what they are observing follows directly from my observation that is calculated directly from Osterberg’s measurements of retinal morphology showing that the maximum (at this point complete!) degree of spatial order appearing as a motif of eight rods surrounding each cone. This perfect geometric array following Osterberg occurs near this eccentricity (really at 7-8 degrees but they are close enough). The interplay of cones and rods at this eccentricity is not statistical anymore but completely ordered! I have proposed that this octagonal motif forms a fundamental (termed “primary”) mid band (“green” or in their terms an “M cone”) light interaction point on the retina. In my explanation this complete degree of geometric spatial order translates into the peak of intensity of the primary mid band wavelength and forms the 550 nm wavelength mid band reference point on the retinal surface. I have proposed that the identification of this geometric reference forms the basis for the color constancy of vision. The eye interprets the exact middle of the visual band geometrically! The retina is not a spectrometer!

I will not go into this much further only noting that the sample size of their images is so small that the statistical nature of the distribution of cones and rods is seen (Osterberg again!). This is as to be expected and they note this. The first degree of order (or “clumping”) that they observe at the 10 degree eccentricity in these statistically small images represents the “tip of the iceberg” of the spatial order that exists at this eccentricity. Their quest for an ordered “mosaic” on the retina, and any idea as to how the randomness that they have observed (until now!) could lead to an image formation mechanism, totally eludes me. I would like to see the reasoning behind this?

The spatial resolution of their imaging methodology and the question why they do not observe rod receptors? I have addressed this in a previous Comment. Suffice it to note that they claim 2 micron resolution which would be approximate the diameter of the inner segment of a single cone and should be sufficient to image rods .

Again, I would claim what they are actually imaging at this eccentricity is a motif of eight rods around each cones. This “M cone” should be really be termed an “M wavelength detection center”

Added on 5/14/08

The authors also undertake a curious (to me) effort to measure the distances between cones apparently to verify the randomness of the distribution. I do not understand why they apparently want to verify what already is, and should be, apparent as the statistical randomness following from the Osterberg morphology data? Their words: “We evaluated the packing arrangement of the 3 cone classes by comparing frequencies of distances between all cones of the same type with those expected based on a random pigment assignment rule”

To be clear - the foveal region that contains > 99% of cones on the retina, and where they want to see a differentiation of these cones into “classes”, is totally “L wavelength” sensitive. Then as rod receptors begin to intrude into the receptor array at the edge of the fovea at eccentricities of one degree a statistical distribution of L and a few M (cone/rod appositions) begins to be seen. At this point if one does not want to believe the data of Osterberg see the figures of George Wald! The author’s measurements until this paper were made at eccentricities of one degree and they observe exactly what they should observe. I would note on the subject of “S” or blue sensitive “cones”, again statistically, here and there an apposition of two adjacent rods will be observed ..and voila, an “S” cone! This is the explanation for the strangely small density of this type of “cone”.

My finding of the three primary wavelength peaks on the retina follows from a simple counting of receptor appositions using Osterberg’s morphology data. Any grad student could do a statistical analysis of the presence of rod/rod appositions in near foveal region (at an eccentricity of one degree as measured by Roorda) and I project that the density so calculated would correspond to these measurements of “S Cones”.

Respectfully submitted.

GCH

5/14/08

I have been enlightened as to the “actual mechanism” of light interaction with retinal receptors that, surprisingly,  this process even today is thought to invoke the concept of treating the receptor as an optical (or fiber optic) waveguide. I had believed that viewing receptors as waveguides was in the past as it has never after significant theoretical study led to any new insights into the vision process. In any event, I am informed that it is contemporary thought that the body of the receptor acts as such a waveguide directing light as a wave (waveguides direct light as a wave!) to the point of interaction with pigment molecules. Additionally, I am informed in no uncertain manner that the smaller rod receptors “are known not to be very effective waveguides”. This is given as the reason why no rod receptors (read none!) are seen in the pseudo colored “cone mosaic” images that are the basis of the work of Roorda et al ⁽¹⁾ and more recently of Masuda et al ⁽²⁾. I was further told that these images are not the light interactive outer segments of the “cones” but are actually of their inner segments! The images follow from (somehow?) the aforesaid classical  guiding of light as a wave through the inner segment  and  after retro-reflection following  light passage through the outer segment where light interaction is known to occur. The function of inner retinal segments (that are somewhat larger in diameter than the outer segments) functions not to interact with light but to serve as a “genetic factory” for the continuous production of the thylakoid disks that form the outer light interactive segment. ?

So to try to summarize this, it is assumed that the receptors of the retina act as light waveguides (which, incidentally, treat light as the wave of classical physics!) and posits that, after light enters the receptor through the inner segment  finally arriving at the outer segment where the light interaction process occurs. One must assume that, in physics terms, the wave/particle duality “happens” (or using Stapp’s statement “a miracle occurs”) somewhere in this passage, the radiation becomes a photon/particle and, following this, interacts with retinal pigment molecules. Vision theory then proceeds into such nonsense as explaining the extraordinary length of receptors , and the stack of thylakoid disks contained within, functioning as some sort of  “photon catch” configuration whose function is to enhance the absorption of photons! This scenario does represent long accepted physics but this is now being superseded as I will show by recent results in nanotechnology. It will become clear that we are now entering an era that will change our views of a great many areas of science - including vision.

In the imagery of Roorda/Masuda (that I am informed has a spatial resolution of 2 microns or a little greater than the diameter of a single cone) rod receptors do not appear at all although they are present in greater numbers than cones, have inner segments and diameters approximating half that of cones, and would seem to somehow, according to well measured retinal morphology (Osterberg and others), “fill up space” in the images of the presented retinal morphology…?? The reason given for the non-appearance of rods is that they, as noted above, “are not very effective waveguides”.

Is any of the above logical?

Enter some modern physics – please!!!!

Historically, there have been any number of treatments of retinal receptors as light waveguides. Noting the work of Jay Enoch and B.R. Horowitz will suffice. It will be crucial to note that these analytical studies - and the above modeling so posits - considered waveguide diameters in the traditional sense used in contemporary fiber optic technology where we assume that light is guided totally within the fiber itself. I would note, parenthetically, that these studies over the years never led to any new insights into the vision process– until I was informed that this modeling is accepted today. This came as a total surprise!

But, enter the modern world. It has been experimentally found as early as 2004, and reported by a Harvard group ⁽³⁾ that when the diameter of the optical fiber is reduced to micron or sub-micron dimensions (i.e., the wavelength of light) light is guided outside of, or around, rather than inside, the body of the optical fiber.

And…these are fiber light guides that are of the dimensions of retinal receptors.

This result directly supports my explanation where light as a wave interacts between adjacent to what will in physics be termed quantum confined electron centers or nanowires - the body of the receptors.

Further in this mode, it is observed that the evanescent field (i.e. the field orthogonal to the direction of light) is enhanced which exactly supports my explanation regarding energy transference to the retinal/rhodopsin complex that is dichroically oriented in this direction within receptors.

GCH

5/12/08

Regarding a Letter to Nature (Nature, Vol. 397, 11 February 199, pp520-522)

This letter titled “The Arrangement of the Three Cone Classes in the Living Retina” by Roorda and Williams is interesting. This (and remember that it is published in 1999) represents the traditionally held view that “Human colour vision depends on three classes of receptor, the short (S), medium (M), and long (L) wavelength-sensitive cones”. The paper then goes on to state that ” these cones are interleaved in a single mosaic” so that “at each point on the retina only a single class of cones samples the retinal image”. I readily admit that I do not know what this means! They seem to assume (as has the history of vision) that the retina acts as the intensity-only sensitive “image plane” of the optics of the eye. This is the plane where photographic film is placed in our camera technology. If this were so, however, there would have to be some logical spatial order to the three light detection centers - as the RGB triads or stripes used in television imaging tubes or camera CCD surfaces. But…there is none of this on the retina - only Osterberg’s asymmetric array of cones and rods. What on earth is assumed here? How is an image (and ,even further , a color image) formed? Is there some logic here that is eluding me?

Incidentally, the asymmetric distribution of cones and rods as measured by Osterberg in 1935 forms the exact basis for my explanation of light interaction with the retina and the genesis of color vision. The meaning of this distribution seems to be explained for the first time

A further sentence in the Roorda Letter states that “although the topography of human S cones is known ^{2, 3}…...” (p.520). If this statement were accurate, namely that the so-called S cones have been shown to exist and that they are arranged in some known topography, I would would have to concede that my explanation of the vision process was incorrect.

I humbly submit, however, that a review of the references cited ( #2 an #3 as noted above), that purportedly support this contention, do not seem at all to do this!!!! I stand to be enlightened but this is my reading of the references.

The Williams reference ² is simply inconsistent with their statement. In the reference, and after considerable effort, a single cone receptor is finally located which is defined as an S cone. One might question how this finding can be reconciled with the assertion that a known topography exists. How is one to ascribe a topography to a single cone?

The Curcio reference ³ is even more curious, again, not at all supporting the statement. This paper relates a much more intensive effort than pursued by Williams to seek the elusive S cone using a number of diverse approaches. But the concluding comment of the paper is most telling stating that “all of the evidence (for the existence of the S cone) must be viewed as inferential only” . The italics are mine but this is the exact term used in the paper. I really do not understand what this means but it is certainly not very positive about the existence of the S cone (or a topography)!

One more note about this piece – as the authors state, their measurements were consistently made “at a retinal eccentricity of one degree nasal from the foveal center”. This region, i.e., at the “edge” of the fovea, is the retinal angle at which there is a greatest interplay of cones and rods – cone density is rapidly diminishing and rods are being introduced into the admixture (again, please take note of the historic data of Osterberg). I would therefore expect to see what R&W imaged at one degree! The pseudocolored images that they present as Figure 3 (p.522) represent exactly what I would expect composed of predominantly red centers representing the long wavelength sensitive cone/cone appositions of the fovea, some number of green centers entering the picture representing the gathering statistical number of cone/rod appositions (and that geometrically define mid band wavelength), and a far fewer number of blue centers characteristic of the, still random at this angle, pairing of rod receptors.

I therefore would agree with the validity of their experimental method recognizing that their measurements were made at one degree of retinal angle. And….these findings at one degree of angle….are in complete consonance with my explanation for light interaction with the retina - and with the long accepted morphology of receptors on the retinal surface.

THERE IS, HOWEVER, ONLY ONE PROBLEM - THE WAVELENGTH DETECTING CENTERS THAT THEY IDENTIFY DO NOT REPRESENT CONES BUT RATHER RECEPTOR APPOSITIONS.

I would propose that if they made a similar type of measurement at 7-8 degrees of retinal eccentricity they would find, accepting that their experimental methodology was correct, that green centers would predominate.

GCH/Ojai,CA

5/7/08

REFERENCES

¹A. Roorda, and D.R.Williams, Nature, 397, No.11, February 1999

² Williams, D.R. et al “Punctate Sensitivity of the Blue Sensitive Mechanism”, Vision Res, 21, 1357-1375, (1981)

³ Curcio, C.A., et al “Distribution and Morphology of Human Cone Photoreceptors Stained with Anti-blue Opsin”, J. Comp. Neurol.,312, 610-624, (1991)

A definition from Wikipedia of the unique color constancy of the vision process”

“Color constancy is an example of subjective constancy and a feature of the human color perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. A green apple for instance looks green to us at midday, when the main illumination is white sunlight, and also at sunset, when the main illumination is red. This helps us identify objects.”

In striking contrast, color photography does not possess this characteristic where the color of an object is not constant but is altered by changing ambient illumination. Color photography requires that filters be used to correct for this effect and render the object of interest close to its’ “true” color.

The vision process possesses color constancy. Color photography does not.

I have written proposing an explanation for this visual characteristic and the reader is referred to Comment of March 3, 2006 on this subject.

Clarifying those thoughts - it follows from Osterberg’s historic retinal morphology measurements and the antenna premise of this work that the exact mid-band point of the visual band (i.e., 550 nanometer) is geometrically-defined on the retinal surface at an eccentricity of between seven and eight degrees. This corresponds to the eccentricity where sufficient rods are present in the retinal motif to completely surround each cone (Osterberg’s data and figures). This provides the fixed reference that Land termed a “fulcrum” from which all other wavelengths of the visual image are compared to produce the hues of “color”. I propose that this fixed wavelength reference provides a basis for explaining the color constancy of the vision process.

I would add that this precise location defines the peak intensity of 550 nm midband wavelength radiation being the location of the maximum density of optical interactive antennas (cone-rod appositions) on the retinal surface. It is the intensity distribution across this band (and across the other cone-cone and rod-rod bands) that Land termed “lightnesses” compared by vision to create the hues of color.

As I have noted, these wavelengths are indeed “primary” but they do yet represent “color”.

Fundamental geometry!

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SUGGESTION FOR INVESTIGATION:

Check the validity of my statement that the 550 nanometer wavelength falls on the retina at an eccentricity of between seven and eight degrees. In a very preliminary effort using LIGHT TOOLS software (Optical Research Associates, Pasadena, CA), and entering the optical parameters of the structures of the eye , it very quickly becomes apparent that this wavelength is incident on the retina at this eccentricity. Subsequent to this effort, I visited with an individual in vision studies who had generated a far more comprehensive simulation than mine (I believe directed to support of the LASIK procedure). I do not feel able to quote this individual as he said that he had not published the data. In any event his simulation showed that 550 nm interacted at precisely the 7-8 degree eccentricity point on the retina. Someone should follow this up!

5/2/08