Rethinking the Process of Vision

I have previously written on this subject (simply search the site using appropriate terms). My thoughts today after reading an article in the New York Times of October 25 “Plugging Into the Eye, With a New Design” by Anne Eisenberg. I have two thoughts  - one on the topic of how these developments are presented in the popular press and the second technical.

First, it pains me that the piece leaves the sight impaired with the hope that the concept of a retinal implants will ultimately restore their sight. The beautiful figure  of an artificial eyeball shown in the piece certainly gives this impression. The fact is, however, that the best that these devices can do, in the  actuial words of the piece, “Most retinal prostheses seem to function to let people detect light and dark”. This is really what I might expect to result when one inserts something near or behind the retina – something happens! When one considers the problem of coupling of such crude imaging devices to the optic nerve…… a nerve bundle that contains some eight million individual fibers……?

I really do not want to be overly negative about these developmental efforts that are being carried out in many parts of the world. This work is only in the very early stages and, again from the piece, “The eye adapts” may prove to be the operative thought and some improvement in vision may ultimately result.

But……..

The point that I have continually made, that forms the fundamental teaching of this work, is that the eye does not function as a camera, i.e., making the assumption that the retina is located at the intensity-only-sensitive “film” plane of the eye. Coming closer to the pixilated solid state devices that are being developed, the assumption is made that the eye behaves as a digital camera. As far as I can determine this is the principle that underlies all of the retinal prosthesis developments that I have seen.

But this is not the case as I explain. Following from Osterberg’s classic retinal morphology measurements, the retina is seen to be a diffractive surface (implying that it forms the Fourier of focal plane of the eye). Now…we do not currently know how to fabricate the retinal light detection elements (i.e., sensitive to light intensity and phase) but, again from this work, we do now know (exactly!) where light wavelengths interact on the retinal surface. Read to the body of this work, but I refer to the finding that the central fovea is solely sensitive to long wavelength (“red”), 550 nm mid band at 8-9 degrees of retinal eccentricity etc.

Again, we do not yet know how to replicate the light detection devices of the retina, but, it would seem to me that application of this knowledge could lead to prostheses that at least begin to mimic the actual process of vision.

And….I believe that technology is available to actually fabricate in silicon the actual light interactive properties of the retina from the fovea to 20 degrees of retinal eccentricity.

I would, as proposed in the past, like to collaborate with any group in this endeavor.

GCH

Ojai, CA

I have often written that “the eye is not a camera”. But I have come upon a more definitive statement in Vision and the Eye by M. H. Pirenne (parapharased from page 120)….“the vertebrate retina….. covers the walls of a camera obscura on which an optical system projects an inverted picture of the outside world”.

This statement represents a deadly shortcut that is the origin of the mistaken view of vision that has been taught for hundreds of years.

The eye is certainly an “optical system” and an “optical image” is certainly the finality, but the steps between differ fundamentally from the camera analogy conjured up in this construction.

The overly simplistic camera analogy implies that the retina is located at the intensity-only sensitive “film” or image plane of the eye. I demonstrate directly using Osterberg’s classical retinal morphology data that this is not the case.

The retina is actually a diffractive surface implying that it is definitively located at the Fourier or focal plane of the eye. This in turn, means that individual light detection elements of the retina, to satisfy the Fourier equation,  must possess the abiity to detect both light internsity and phase of detected light. I have described the light detection structures of the retina that accomplish this.

How long will it take vision science to understand and correct this ?

GCH

Ojai, CA

10.26.09

Begin by forgetting (or “unlearning”)  what you have been taught about light interaction with the retina and the  process of vision ( for example as heretical as it sounds, use of the terminology  “rods” and “color sensing cones”).  Completely start  over in your thinking even going so far as to examine what you really mean when you use the term “color” - it has been grossly misused as I will explain below.

Now…abstractly….the plane of retinal outer segments that everyone agrees is the plane where light is absorbed should be considered as no more than a circularly symmetric array of identical nanowires with incident light pervading  and completely filling the space between  them.

(Defining a “nanowire” - one might consider that this is the “central core” of  each individual retinal receptor or, alternatively, “the string of retinal molecules held within the rhodopsin protein structure that form the length of each  receptor”. It  is a space  of approximately 50 microns in length  (corresponding to the vertical dimension of an outer segment ) with a diameter of approximately ten nanometers  (or 10-8 meters) corresponding to the “quantum confinement dimension” of the electron.)

Light  incident on the retina is absorbed laterally from the surrounding space along the entirelength of each nanowire.

THIS IS THE CORRECT VIEW OF THE RETINA. Now unlearn all of the historically incorrect ideas about cones and rods and “photons interacting with pigments within receptors” and on and on……!

Moreover, in the above construction all nanowires in the array are identical. It is the dimensionality of the spaces between them that determines the light wavelength absorbed. And, this dimensionality geometrically dictates, as taught by this work, that three  and only three wavelengths are absorbed.

It should then be seen  that the nanostructure of the retina absorbs light as the wave of classical physics  in the space between nanowires with this absorption being necessarily adjacent to quantum spaces that corresponde to the electron absorbing mass. Each individual light detection site performs this fundamental physics transition.

There are thus two distinct steps in the process of light detection and vision. The first occurs at the point of the interaction of light with the plane of receptor outer segments. This step is effected in the quantum femtosecond  (10-15 sec) time domain. The  electronic signal used for subsequent processing  is generated at this step corresponding to the quantized electron generated from absorbed light energy. The subsequent processes in the “sub-retinal cicuitry”  of the retina serve to thermalize (or slow) the interaction to human nervous system proportion.

THE VISION PROCESS AT THE POINT OF INITIATION IS A QUANTUM PROCESS TRANSFORMING THE LIGHT WAVE  OF CLASSICAL PHYSICS TO A QUANTIZED ELECTRON PARTICLE AT EACH OF THE MILLIONS OF LIGHT DETECTION SITES ON THE RETINA.

The common identity of nanowires follows from the electron quantum-confining and retinal molecule that is ubiquitous to each one and that forms the endpoint of the light energy absorbing process. In traditional thought this molecule is known to be common to both cones and rods so there should be no problem in accepting this. These nanowires then are fundamental generic quantum-confined electron spaces that function as the “absorbing mass” of the light interaction process.

Imagining that each nanowire is the analogue of an optical fiber it has now been experimentally demonstrated (referenced in the body of the work)) that light flows around and not through the fiber when it’s diameter has been reduced to sub-optical wavelength dimension – as is the case here.

Wavelength absorbed by each nanowire is then controlled by the newly considered (this work) geometrical spacing of the array – and not as traditionally thought by “pigments”. The finding of this work that “an admixture of two spacings yields three specific spacings” then, consistent with the measured plan of the retina, verifies the trichromicity of the light interaction process of vision.

…but, crucially, the three wavelengths so absorbed DO NOT YET CONSTITUTE THE HUES OF COLOR! We have made a fatal  shortcut that “wavelength” and “color” are the same. The perception of color is the result of subsequent (to the initial retinal light interaction) processing of light intensities that fall on either side of the geometrically determined mid band point on the retina ACCORDING TO THE SEMINAL WORK OF EDWIN LAND.

Using an analogy pursued by Land (among others) color  represents the music and individual wavelength  interactions the underlying notes!

The true genius of Edwin Land never ceases to amaze me!

The chores of the day intrude and I will continue this shortly.

GCH

Ojai,CA

Disregarding  the facile quotes about the quantum such as Feynman’s “quantum physics deals with nature as she is—absurd”, I always remember what I thought was  Wolfgang Pauli’s truly meaningful  piece of insight that (paraphrased) “nature only answers when you ask the right questions.”

I have always been uneasy with the Schrodinger Cat paradox. I  certainly understood that  it  was an exercise contrasting the quantum and classical views of reality,  but  in the main I dismissed  my reservations as just a lack of  understanding on my part. Yesterday, however, I came upon an item in Economist.com that again attempts to describe the paradox and the thought occurred to me that, in the light of my work, does the paradox really ask the right question?.

The teaching of my work on light interaction with the retina of the eye demonstrates that there are two widely separated time domains operative in this interaction. These are: a) the fast “quantum-associated” time of the order of femtoeconds (10^-15 sec) or less that is consistent with  the experimentally demonstrated isomerization of the retinal molecules within receptors during the initial light interaction, and, b) thermalization of the absorbed energy in transit through the lipid membranous structure of the thylakoid disk that forms the body of the receptor, to a slower “biologically useful” time associated with biochemistry, nerve transmission etc.

Thus, two distinct times separated by perhaps thirteen orders of magnitude are involved in light interactiion with retinal outer segments “

I propose that these correspond to the separation of the classical and quantum view of physics and this classical/quantum interaction is effected at each of the millions of light detection sites on the retina. This is the function of the retinal nanostructure as I describe it.

How might all of this be associated with the Schrodinger’s Cat paradox? It occurs to me that two distinct time domains must be operative in the Schrodinger mental construction analogous to the proposal that I make defining a classical/quantum interaction (or transition) on the retinal surface. Separating …the first, accepted quantum nature of the radioactive decay process and, secondly, the slower (classical) nature of subsequent what must be termed classical actions – opening the box, movement of the hammer, etc.

It is obvious to me how this time separation is bridged in the light interaction with the nanostructure of the retina. How can the overtly-classical construction of the S. paradox ever bridge this time separation?

Are we asking the right question?

GCH

Ojai, CA

10.15.09

This explanation represents the first rational interpretation of the long accepted  (in every textbook) classical measurements of retinal morphology made by Osterberg in 1935 and clearly shows that the retina is a diffraction surface composed of three concentric rings of narrow wavelength response that correspond to the wavelengths that have been traditionally thought to be chromatic “aberrations”. This response represents the fundamental image-forming mechanism of the eye. There was never any discernible spatial ordering of “color-sensitive cones” on the retina that would indicate that this surface behaved as color film at the image plane of a camera - although this irrational model (i.e, not in consonance with any measurements) has been assumed for over a hundred years of vision science.

As I long ago noted, George Wald, who won the Nobel prize for his work on vision, clearly saw this in his experiments but the paper, Blue-Blindness in the Normal Fovea , has seemingly  received scant attention in the field. In the course of my work someone who should have known actually said to me: “Wald was a good experimentalist but…….). The foveal region then, that contains greater then 99% of all cones, is insensitive to blue, i.e., contains no “blue sensitive cones”. This is exact agreement with my explanation.

I’ll make this point inconspicuous by using a smaller font- but a diffractive surface shows that the retina forms the Fourier or focal plane of the eye. To form an image satisfying the Fourier equation, each light detection site on the retina must possess the ability to detect both the intensity and phase of received light. I have shown in this work how these sites are able to accomplish this.

See previous comments of mine to the point that the diffractive retinal surface is electromagnetically “tuned” to three precise wavelengths and that these wavelengths do not yet represent the sensation that we term “color”. They do represent, in this explanation, the precise ends (or limits at 400 and 700 nm), and, most importantly, the exact geometrically-defined center, i.e., at 550 nm, of the visual band*. One must think about this – the wavelength of light is associated with, or determined by, geometry in this biological system! And further, (see my “Rosetta Stone” diagram), a geometric construction of a mixture of two wavelengths determines an exact midband reference wavelength! Amazing!

* The presence of this fixed reference would seemingly explain the long standing unexplained conundrum of the “color constancy” of the vision process. See this link on the homepage where this is discussed.

It then becomes clear that the finally defined diffractive surface of the retina together with the unique finding of a precise mid band reference wavelength validates Edwin Land’s extensive model of color vision. Land termed this mid- band reference a “fulcrum” and to quote his words: “…we have learned that the eye must have a fantastic mechanism for finding a balance point within a band of wavelengths”. We have finally identified Land’s “fulcrum” – it lies at a retinal eccentricity of 8-9 degrees or, geometrically, where the density of smaller rod receptors is first sufficient to completely surround the remaining larger cones in octagonal symmetry*

* I believe, and have written about, there being further meaning to this symmetry).

The mechanism underlying Land’s model thus becomes clear. The sensation of color (or the “hues of color” or the point where the term color should first be used) is determined, as he proposed, by the eye defining the ratio of intensities (Land termed them “lightnesses”) on either side of the, now defined, fixed wavelength reference.

In my view, Edwin Land was the unheralded true genius in the history of vision!

GCH

Ojai, CA

10.02.09