Rethinking the Process of Vision

Reading the New York Times this morning prompts me to write again about the MD condition and its connection with my explanation of light interaction in the eye. It is my premise that the fundamental cause of the MD condition is the entrance of ultraviolet radiation into the eye with the eventual result, after perhaps many years of insult, being irreversible biological damage to the macula/retina. The only thing new in this statement is my emphasis on the term fundamental. Public statements go on to parse the condition defining various medical states of degradation (wet or dry MD?) and pointing to regimens of vitamins and minerals that probably have the effect of rendering the retina healthier and staving off eventual degradation. But I would claim that the fundamental issue involves UV radiation.

I have found (discussed in other parts of this page, with references) that the wavelength of light is associated with constriction of the pupil of the eye. This connection seems not to be well understood it being generally assumed that light intensity is the sole controlling factor in pupillary constriction. The size, or diameter, of rod receptors determines, through the dimension of rod-to-rod apposition length, the (probably) exact short wavelength limit of visual response. The 400nm wavelength generally quoted as the limiting wavelength was undoubtedly evolutionarily selected as it is just at the point of a biologically-damaging UV threshold. I have proposed that the rod array of the peripheral retina acts jointly as the “light meter” of the eye controlling, through pupillary constriction, light – and particularly short wavelengths – entrance into the eye. I would therefore propose that if one wants to look for a genetic basis for the MD condition it will be found in the factors controlling the diameter of rod receptors on the retina.

I add what I had written on this subject on April 14th, 2003

On Blue Light And Age Related Macular Degeneration (AMD)

One proposal of this model is that the peripheral retina, i.e., the predominantly rod-containing area beyond approximately twenty degrees, is integrated (rod receptors connected in parallel) to generate the signal that controls pupillary constriction and light entrance into the eye. The peripheral retina then becomes, in effect, a “light meter” functioning to control the amount of light to levels that preclude damage to sensitive eye structures. It seems widely held that light intensity alone (i.e., luminance) controls pupillary constriction. A less obvious question asks what effect wavelength might have on constriction and, if so, what is the most effective wavelength or wavelengths?

This question seems not to have been intensively investigated but one paper by Drew et al (”Pupillary Response to Chromatic Flicker”, Exp. Brain Res., (2001) 136, pp256-262) found that hue (color) modulated flicker has a much greater effect on constriction than a luminance modulated signal. Their words: “red-blue color-paired flicker consistently produced the strongest constrictions. These responses occurred even when the flicker was of a lower luminance, both physically and perceptually, than a preceding non-flickering color, indicating that chromatic rather than luminance-sensitive mechanisms are involved in this response” (my italics).

George Wald in his Nobel lecture reported that the peripheral retina was monochromatic but he did not go on to specify wavelength. This result is in consonance with this model but we go on to find and predict that the rod-rod appositions of this portion of the retina will render it solely sensitive to short wavelength (blue) light. Moreover, we propose that this provides a fundamental basis for the fact that 400 nm forms the short wavelength limit of visual response. But important here: we propose that blue light controls pupillary constriction.

It would seem that nature would have so designed the system using this highest energy radiation to control light entrance into the eye abutting as it does the damaging UVA region (320-400 nm).

It has been asserted that the yellow carotenoid pigment lutein present in the eye has the function of absorbing UV radiation preventing damage to ocular structures. We would propose that this pigment does so function but provides a “second line of defense” against UV in individuals exposed to excessive sunlight where pupillary constriction alone cannot provide sufficient protection. I would like to see a study of the lutein concentration in the eyes of individuals as a function of sun exposure in their occupation etc. Has such a study been made?

The onset of age related macular degeneration (AMD) may be related to a loss of the ability to constrict the pupil of the eye as one ages. Is there a quantitative measure or test of pupillary constrictive ability - quantifying the “strongest constrictions” seemingly measured in the above cited paper by Drew et al? Has such a study been made?

Thus I propose that there are grounds for the proposal that there is a connection between higher energy, i.e., blue radiation, and the onset of AMD. Reinforcement should be given to the advice to wear blue-blocking sunglasses etc to minimize this specific wavelength into the eye.

The fundamental rule of this hypothesis is that the geometric rod-to-rod distance (mediated by the diameter of the inner segments of these recep;ors) in the peripheral retina sets the discrete short wavelength limit of visual response - not “almost” but the exact limit. I have assumed this to be 400 nm as this is the oft quoted value. But…there are probably genetic differences in the size of rod receptors among individuals. Supposing that rods were slightly smaller… this would shift the short wavlength limit towards, or into, the damaging UVA region. Might it be found that rod size varies in this manner in individuals suseptble to AMD?

GCH

When viewed from this new perspective the retina is seen to be organized according to geometric principles to detect three optical wavelengths refracted by the chromatic aberration (or, what has heretofore been termed an aberration) of the lens and structure of the eye. This organization is simple and geometrically precise. But….why only three wavelengths? Wouldn’t nature, to detect the full panoply of hues that we term color, have configured the retina to detect all wavelengths within the visible band? Employing the geometric principle of the concept, this would require a large number of different receptor diameters logically arrayed from the fovea to the retinal angle corresponding to the short wavelength limit of the band. But..nature seemed to hit upon a simpler scheme based on only two diameters of receptors – the cones and rods. By intermeshing these two diameters an array results that detects three separate bands but in a unique manner – as the brightness or intensity profile of each band thus providing a unique principle of geometrically distilling the intensity of each band from the light detection process…for subsequent synthesis of the full color signal …..as Edwin Land saw!

I again suggest that the Roorda group extend measurements (Nature, Vol.397, pp 520-522, 11 February 1999) of the color sensitivity of retinal receptors, using the same imaging and bleaching modalities, to beyond the one degree retinal angle reported in their Letter. I would like to see analogous images taken at 7-8 and 20 degrees. I would predict that they would observe an increasing density of green centers (which they term “cones”) until at 7-8 degrees the field would be all green. As one measures further to the 20 degree angle blue centers would begin to predominate.

GCH

The fundamental lesson of this exercise is that the teaching of light interaction with the retina of the eye, supported by the physics of visible light interaction with the recently discovered porous silicon nanostructure, is that in both cases light interacts as the wave of classical physics immediately and necessarily adjacent to an absorbing mass comprising quantum confined electron sites. I believe that this should properly be termed a “quantized interaction” a term that, importantly, violates neither classical or quantum physics. How much has the concept that “a photon interacts….with a pigment etc.” led our thought process astray? I quote again a sentence from an exposition on quantum electrodynamics “Paths Not Taken” (mathpages.com/rr/s8-09.htm) to wit “ To speak about the trajectory of a free photon is to speak about something that cannot, even in principle, ever be observed”.I expect that this will elicit controversy but it follows from phenomenological observations that I find difficult to refute – and that explain so much!

So..I would propose that anyone thinking about “streams of photons being guided down the length of retinal receptors and being statisically caught by pigment molecules using the photon catch hypothesis” consider an alternate scenario that is actually taught by the structure of the eye and recent dicoveries in optics, namely that light as a wave travels outside of the receptors, in interreceptor spaces, and imparts energy to the correctly dichroically oriented pigment molecules in a now understood mechansim along the entire receptor length.

GCH

The basic premise of this work is that the retina is structured as a logically spaced, 2-dimensional periodic array of light detection centers. How did this evolve? The specific periodicity that is identified leads to an understanding of the underlying physics principles that evolutionarily led to this structure…and I propose that the morphology of the retina is actually a 2-dimensional moire pattern objectification that resulted from the incidence of unpolarized light..onto primordial biological substance.

I have referenced (see my previous Comment 0f 2/6/06 “Evolution and the Retina - An Experiment”) the result in optical physics that the wavelength of light impinging onto a surface is reflected laterally (i.e., orthogonally or transversely) to the direction of incidence onto that surface. This is not intuitive as it might be expected that it is the intensity of light and not wavelength that should be so reflected. In this phenomenon an optical “grating” is formed on the surface whose period exactly corresponds to the wavelength of the impinging light beam. In these experiments the light beam is plane polarized and a one-dimensional structure (i.e., a grating) is formed.

Now, what might happen if the light beam were not plane polarized but consisted of unpolarized or randomly polarized light? Isn’t it logical that the periodic nature of the resulting structure would be maintained but in “circularized” two-dimensional form? Such a structure would be composed of an array of circles whose periodicity might correspond to the wavelength of the impinging light. This corresponds exactly to the array as described in this work of circular retinal receptors - the cones and rods! Thus, I posit that these biological light interactive structures were evolutionarily formed by this mechanism. The periodic “optical antenna” structures that I have proposed correspond to the periodicity inherent in this line of thought..logically spaced (wavelength defined) arrays of periodic, “absorbing mass” centers (quantum confined electron sites).

I have proposed that it is the dimensionality of the array of the larger cone receptors that specifically defines the ~700 nm, long wavelength limit of the visible band (why nature chose this particular wavelength I leave for others to consider). Geometrically, such an array of circles of the same size results in hexagonal order. Cone receptors are close packed in this manner so that for a single wavelength it might be said that hexagonal order seems to be the fundamental nature of things.

If one goes on to consider the array of rod receptors that comprise the bulk of the retina, the same mechanism is operative although the periodicity (and thus receptor size) is correspondingly smaller due to the shorter light wavelength. Rod periodicity therefore corresponds to the short wavelength limit of visual response at ~400 nm with, again, the receptors being hexagonally ordered ( I have proposed that the 400 nm wavelength is dictated by the energy of light - any sensitivity to shorter UV wavelengths would result in damage to the biological system).

Now the overall organization of the retina can be described as a radially distributed array of receptors where the hexagonal order of smaller rods begins to “intrude upon”, and become admixed with, the hexagonal order of the larger central cones. At some point in this intrusion there is a point where rod density is sufficient to completely surround each cone. In the human retina this occurs at retinal angles between 7 and 8 degrees (as measured from the central fovea). I have discussed at some length the octagonal spatial order that results at this point noting that (refer to my “Rosetta Stone” diagram) this radius geometrically defines the exact mid-band point of the visible band.

(I have also noted a number of other strange geometric factors following from the distribution and sizes of retinal receptors, namely that octagonal symmetry of rods-around-cones that results at this point and that the same symmetry seems to be present in the visual organs of many (perhaps all?) species as reported in the work of Snyder).

From the viewpoint of this discussion, however, octagonal order at this point is not in the least bit strange but is rather a seemingly logical geometric result of the intermixing of two receptor sizes.

Thus both of the endpoints and the exact enter of the visible band of vision are defined by physics and simple geometric principles.

The realm of semiconductor physics may provide a way to demonstrate the validity of the above projections.

GCH

I.

“I believe that it is now possible to turn one’s attention to external reality beyond the eye.. what is actually perceived by the eye….as discussed so eloquently by Land. In the Fourier domain, retinal architecture must somehow correspond to the “diffraction pattern of perceived reality”. I am fascinated by the thought that as antennas are perfectly capable both of absorbing and radiating electromagnetic energy might the eye then not be the “passive optical receiver” that has for so long been assumed? Is it possible that the eye “radiates” some albeit photon level signal into the visible spectrum and that this might bear on what is perceived of external reality? Might such a “two way optical interrogation” of external reality bear on consciousness - at least via the visual pathway?

Although it will not be obvious until one studies the paper, it is uniquely the presence of two sizes of receptors admixed on the retinal surface determining a geometric mid band point that allows the sensation of color to be perceived. VISION IS TRICHROMATIC ONLY BECAUSE THE HUMAN RETINA CONTAINS TWO SIZES OF RECEPTORS! This predicts that any specie with only one size of receptor will have only a very narrow window of vision - and no sensation of color”.

II.

REGARDING A POSSIBLE CONNECTION BETWEEN THIS NEW PARADIGM AND CONSCIOUSNESS

The antenna aspect of retinal receptors that I have proposed would seem logically to lead to the idea that the eye might transmit or radiate signals rather than acting as the passive optical receiver that has been held for so long. Further, I have proposed that such antenna receptors might act as “phase conjugate mirrors” (in fact, the ultimate phase conjugate mirror) redirecting light rays back upon the exact path that they used in entering the eye (ref.1.). Such re-radiation would lie in the the three bands to which (in my proposal) the eye is “tuned”, i.e., wavelengths lying at (and defining) the ends of the visible band and a wavelength corresponding to the exact center of that band.

I have noted the similarity between the nanostructures of the outer segments of the retina of the eye and that of recently discovered visible light interactive “porous silicon”.There is actual evidence for similar re-radiation in solid state porous silicon specifically in experiments ( by investigators at Spire Corporation, I believe) injecting electrons into the PS nanostructure and observing emitted visible radiation - in essence, creating silicon light emitting diodes. Thus the structures behave in classical antenna fashion both absorbing and transmitting visible light.

Now…applying the same idea to looking into someone else’s eyes - the eye and the retina have been described as extensions of the brain - which they surely are - one can conceive an actual physical mechanism for subliminal communication or connection between the brains of such individuals mediated by specific resonant wavelengths of the visible band.. There must be an actual resonance between the two retinas in such a situation.

What would confuse such a scenario? We know that individuals perceive colors (wavelengths) differently. In this model the cause of this would be a slight, genetically mediated, difference in the lateral dimension of the inner segment (or segments) of retinal receptors. Such a difference would alter the visual bandwidth of the individual and, as Land demonstrated, perception of color (any bandwidth difference “off sets” the crucial midpoint of the band and significantly alters perception of color). In such an instance any two retinas might not be “in resonance”… upsetting “conscious communication”. Fun!

ADDED 11/04/03

If the reader will consider the text quoted below regarding the strange characteristics of a phase conjugate mirror I would note that any “re-radiation” from the eye as I propose would not extend over a large solid angle (which would require power) but rather would, as PCM behavior would dictate, only trace backwards the path that it took upon entering the eye. This would require insignificant power. The more one thinks about this the more one envisions a “connection” between the image perceived and the brain of the perceiver!.

(1) For a popularized summary of optical phase conjugation see “Applications of Optical Phase Conjugation - Time Reversed Light”, David M. Pepper, Sci. Am., January 1986

(2) “Optical Phase Conjugation”, Quantum Electronics Series, Robert A. Fisher, Editor, Academic Press, 1983.

A fascinating excerpt from page 3 of the latter reference:

“…..consider what would happen if one were looking into a phase conjugating mirror: an observer would see his or her face in a conventional mirror but not in a phase conjugator. This is because any light emanating from a particular point on the face would be returned by the conjugator to that same point, thereby not entering the viewer’s eye The only light seen by the observer would be that which had struck the conjugator after emanation as a diffuse reflection of room light scattered from the cornea covering the pupil of either eye. If the observer increased the illumination of one eye (perhaps by using a flashlight) the entire conjugator would appear, to that eye only, to become relatively brighter. Obviously, the viewer’s observations would be unaltered if an aberrating medium were placed between the viewer and the conjugator….”

AND SOME TEXT PREVIOUSLY WRITTEN……

I believe that the basis for again a physics-based mechanism for consciousness might follow from a combination of advanced thoughts. It would have three elements as follows:

a.) The proposal of Julian Barbour (1) that time itself is an illusion - that the universe is composed solely, as Ernst Mach proposed in the last century, of “things” and “configurations”. In this line of thought, as Barbour proposes, we “travel a timeless path between these configurations or states”. Another term for these states might be the timeless “instants” dwelled on by Einstein and even philosophers such as Schopenhauer.. The specific “path” upon which we find ourselves is determined by the operative term of quantum reality, i.e.,- probability, with this path determined by the “history” (another important concept of Barbour’s) inherent within it. Crucial to the concept is the “many worlds” hypothesis of Wheeler/Dewitt that would propose that it is not the most probable state (from quantum theory) that “exists” - but that all states simultaneously exist (a very comforting thought). W/D saw this an alternative but valid interpretation of the mathematics of quantum theory. My apologies to Barbour if I misstate any of the elements of his theory - but it is obviously a very difficult concept!

Secondly,

b.) The definition of “memory” (which could be, for example, either biological or silicon based). We invariably describe and think of this function as the “storage of information”. The word “storage”, however, is a” time-loaded” word implying that information “resides somewhere for a period of time”. I propose that memory might equally be thought of (to satisfy Barbour’s “timelessness”) as a function of “changing configurations”, i.e., a function with the “capability for the rearrangement”….. of neurons in the brain (as usually proposed in memory concepts) or of bits or bytes on a silicon chip.

And lastly,

c.) My proposal that a function of the retina in detecting light is to “abstract timelessness” from externally perceived reality via the character of a Fourier interaction with the retinal plane (which I propose is the Fourier or focal plane of the eye)………. together with………my proposal that the “antenna” nature of retinal receptors might be found to radiate into, and thus “interrogate” (or “couple with”) external reality . If the vision process had evolved to “radiate into” something there is the strong implication that there must be “some function to radiate into” implying some interactive process.

NOW.. the proposal….

….that the physical mechanism underlying consciousness might be “the direct connection between a radiating character of the antennae of the retina and the function of “changing configurations” (as defined above) that we term “memory” in the brain”. I mean by this a “two way” connection that to me connotes “coupling to external reality” or consciousness. Barbour’s timelessness is crucial as we would seem to be proceeding from one “timeless configuration state” to another. This follows from my view of the “time coherent” (or “timeless”?) nature of the Fourier interaction with the retina (perhaps the most fundamental characteristic of the Fourier plane of a converging lens is that all light rays are brought into time coincidence at that plane …and such coincidence might be construed as “zero time” or timelessness)..

The analogy here might be to a “radio transponder” with that piece of technology composed essentially of an antenna coupled to, at least, a logic processing system - but without memory. A better analogy (but one perhaps not yet as well understood by the general public) might be with the now becoming popular “wireless ( or “wi-fi”) computer networking schemes where, again, an antenna is coupled to a receiver but one that now contains the memory function of the computer. Such a “wireless” computer can be seen to be “interrogating external reality” and processing information as a “function of changing configurations” in exactly the mechanism proposed above. Does such a computer possess at least a little of the basic rudiments of consciousness?

I realize that there are seemingly other “inputs to consciousness”. These include the interaction of sound waves with the cochlea of the ear (surprisingly again involving the Fourier transforming process!), the sense of touch (we do radiate thermal wavelengths!) the sense of smell . etc. Perhaps vision is the primary one?

A fundamental question would seem to be what would the eye be” interrogating”? What is the interactive process or processes involved? I propose that one of the more satisfying answers follows again from Barbour’s thinking suggesting that this function somehow “bridges” one instant (or “configuration”) to the next in a timeless universe.

I THINK IMPORTANT - I have proposed under the link “Additional Thoughts….” that a recently discovered phenomenon in laser physics - “time reversal and optical phase conjugation” may be involved in light interaction with the retina. .In this process light waves are precisely redirected back along the exactly same path after being reflected from the phase conjugate “mirror”. The retina as I view it appears to have exactly the properties of a phase conjugate mirror. Any such “redirection” only becomes apparent with the invocation of antenna behavior and the capability for encoding light intensity and phase which is the fundamental premise of this model.

Gerald C. Huth, Ph.D.

Ojai, CA
11/29/02 (Revised 8/12/03)

(1.) Julian Barbour, “The End of Time, The Next Revolution in Physics”, Oxford University Press, 1999

Allan Snyder’s published work contains in my view some of the most important considerations and observations of the eye and vision process. It was from one of his papers that I learned that the same octagonal symmetry of rods-around-cones on the human retina is seemingly present in the visual organs of all species. (I consider this geometrical consideration important and it is discussed elsewhere in this work).

My thoughts from one of his papers: (A.W.Snyder, P.A.V.Hall, “Unification of Electromagnetic Effects in Human Retinal Receptors with Three Pigment Colour Vision”. Nature, Vol. 223, August 2,1969)

The general discussion of this paper centers on the physics of power absorbed in retinal pigments but the authors conclude:

“Spectrophotometric measurements measure the power….absorbed by the photosensitive material of the outer segments. Three P(lambda)s have been measured. It has been concluded from these experiments that three individual molecular substances …are present. Because, however, three photopigments have not been extracted from the human receptors, this conclusion is speculative in that it ignores the electromagnetic effects M(lambda)”. (bold text is mine).

(I would note here that my review of George Wald’s work revealed the same thing..Wald, after identifying the one chemical pigment specie (rhodopsin) searched diligently for the “other two” that he felt must be present…he could never find them!).

Further on on p.527:

“We conclude from the above discussion that there is no definitive evidence for three molecular substances mediating colour vision; however, it is established that three receptors (pigment responses as defined above) do exist”.

(The reader will have become aware that I conclude that the established three receptors are the three receptor appositions of the retina).

From the following paragraph:
“An alternative interpretation of the spectrophotometric experiments, which also provides an explanation for the difficulty of extracting three molecular photosensitive materials, follows from considering only one S(lambda) but three M(lambda)s produced by three types of receptors,….There are a number of convincing mechanisms by which this could occur; one possibility is that the identical molecular substance is arranged differently in each receptor type”.

(I must define the S and M terms used in the above: the power P absorbed by the pigment in the outer segment is the product of S and M where S is the “spectral absorption property of the pigment molecules independent of their physical arrangement and situation in the outer segment” and M is the “electromagnetic spectral property..a complex function of wavelength taking into account the spatial relationship between the molecules and the electromagnetic fields”. It thus seems clear that the model that I propose can be interpreted in the context of the above!).
S is the spectral property of pigment molecules that is usually, and solely, considered in vision science measurements. M, however, is the crucially important factor that determines how the pigment molecule is affected by it’s electromagnetic environment….and the essence of the concept proposed herein.

And, if one has any doubt that the rhodopsin complex is labile and thus able to rotate freely in an electromagnetic field, from Hargrave (“Molecular Dynamics of the Rod Cell”) p.218,
“The Disk Membrane Bilayer is Highly Fluid”, “..it became clear that proteins (referring to the photoreceptor rhodopsin proteins ) were able to freely rotate about their axis and to diffuse laterally within the plane of the lipid bilayer (ref)”. And later: “Fluidity of the disk membrane is equivalent to that of olive oil (ref)”.

Now.. Now……I realize that it will be argued that, subsequent to this work, “genetics has succeeded in identifying the three pigment species at issue”. But..please think!…following from my comments of the past few days…the species that have been genetically identified (and formulated) are simply three variations of the rhodopsin complex (each containing the same ubiquitous central retinal molecule) whose optical properties will be altered in the final environment in which they find themselves through the electromagnetic spectral property term M in the above.

The final optical response of pigment molecules depends on the specific electromagnetic field surrounding it and this, in the retina, is determined by nanostructural considerations.

I am always tempted to delve into, and bring into the discussion, the murky (but well understood) deeper physics of the light interaction with matter that is the subject of this work. The terminology of quantum electrodynamics would have to be introduced (such as “an emitter has at each instant along its worldline a particular complex amplitude for emitting a photon”) but it is easy to see that this would take any discussion away from what has been my original intent….to articulate the idea in a way that I thought would be understandable to the largest segment of the vision science community. [… More»]

I believe that it is possible to recreate in a silicon nanostructure the evolutionary processes that led to the human retina. I propose a singular experiment that I believe will start along the road to substantiating this claim. [… More»]

In regard to ”Packing arrangement of the three cone classes in primate retina”, Roorda et al, Vision Research, Vol.41, 1291-1306, (2001)

The authors begin with a perceived dilemma in their Introduction. I will quote from the first paragraph:

“Spatial vision and color vision depend on the same mosaic of cone photoreceptors, yet their demands are different and to some extent in conflict. Fine spatial resolution is best served if photoreceptors all have the same spectral sensitivity, so that local variations in the signals originating in different cones represent only differences in intensity and not differences n spectral composition. On the other hand, to resolve fine variations in the spectral composition of a scene requires neighboring photoreceptors to have different spectral sensitivities. The visual system must therefore inevitably compromise in balancing good vision against good color vision.” [… More»]