Rethinking the Process of Vision

It is my premise that the literature of vision science has historically made a crucial mistake in  conjoining the concepts of electromagnetic wavelengths with (the hues of) color – that “long wavelengths actually represent the color red” etc. This shortcut has had major consequences.

To begin, It is certainly well understood  that the light interaction process on the retina occurs at the plane of the outer segments of  cone and rod receptors. At that point, however, an assumption is made that photons (”light particles”) interact with three pigment molecules residing in the  cone and rod retinal receptors. This has led to absurd hypotheses such as the “photon catch” notion as the reason for the length of receptors. In contrast with this model it is the basic finding of  this work, however, that this light interaction fundamentally involves detection of light as the wave of classical physics. It becomes clear that the structure of the eye simply evolved to use the principles of the refraction of light to detect light in this manner, i.e., interacting with the wave nature light and not as “incident photons …interacting with retinal pigments, etc” as has become dogma in modern thinking.

This electromagnetic wave interaction process occurring at the point of the retinal outer segments is, in singular physics terms, the fundamental process of vision. Interaction with the outer world is determined at this point and, as shown in this work, lies in the realm of  the quantum - actually performing the transition from classical to quantum physics . Absorbed light wave is transduced at each light detection site on the retinal surface to quantized electron particles that serve ultimately to form the “real world” visual image that we see.

The spatial aspect of this interaction  on the retina is defined by a heretofore unrecognized geometry of the nanostructural organization of retinal receptors. At the risk of using another shortcut,  it is “optical antennas” (read “spatial entities”) that absorb the wave nature of incident light. Further, this interaction occurs in the plane of outer segments in very fast, (quantum) or ~10^-15 second time. The physics of light interaction on this plane is the fundamental nature of the vision process.

All subsequent steps in the formation of the visual image within the retina are biochemical in nature that, in effect, “slow down” the information bearing process in time to human nervous system proportions.

The shortest electromagnetic wave detected on the retina is known to be near 400 nanometers with the longest wavelengths (the upper end of the visible spectrum) at 700 nanometers. At this point light is still considered a “pure wave” without any implication of the term “color”.

It seems helpful here to get some idea of the spatial antenna lengths on the retina that would be resonant with, and therefore absorb, these wavelengths.

Using the antenna equation: L = λ/2n where antenna length L absorbs (or is resonant with) an electromagnetic wavelength divided by twice the index of refraction of the absorbing medium. The diameter of a single rod on the retina is about one micron (10^-6 m). The light absorbing antenna length therefore should be 400 nm / ~2.6 (using 1.3 as a refractive index for the retina) or of the order of 150 nm. The corresponding length for the 700 nm long wavelength limit of vision is longer at ~270 nm. These values are smaller than the center-to-center distances between adjacent cones and rods (~1.8 and ~1.0 micron) but are sensible relative to the requirements (discussed in the body of the paper) for a portion of the length (lipid membrane) to involve time-transitive thermalization of the absorbed electromagnetic energy. There is much to be learned about this fundamental nanostructure that translates the wave of classical physics to the quantum nature of the absorbing electron.

It remains that the retina is nanospatially “tuned” to three – and only three – single electromagnetic wavelengths that correspond to cone-cone, cone-rod, and rod-rod appositional distances (how many times have I said this!).

Crucial to what comes next – sensing the hues that we term color – the center, cone-rod apposition geometrically defines the exact center of the visible band. A spatial geometry is associated with, or determines, an electromagnetic wavelength

These three wavelengths therefore must certainly be considered “primary”- but are still “wavelengths” and not yet the hues of color! Young et al many years ago correctly deduced the trichromicity of the vision process but the field went astray in associating these (shortcut) with colors!

Now enter the profound insight of Edwin Land regarding color vision. The above finding of a precise mid band reference wavelength on the retinal surface directly supports what Land deduced from external measurements. I have discussed Land’s work before and I leave it to the reader to review this.

In summary, the sensation of the hues of color must be the province of the brain with the initial visual interaction with the outer world formed at the plane of retinal outer segments at the point of transition between the classical/quantum time domain of physics. Future understanding of vision will involve the discipline of physics!

A thought experiment - with the knowledge that the short wavelength limit of the visual band is narrowly “tuned” to a single , or at most a VERY narrow band of wavelengths consistent with spatial dimensionality, how should we describe  which of the many hues that we term “blue” will we see?

GCH

11.13.09

Ojai,CA

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The following drawing is from Pirenne’s Vision and the Eye (Plate 6 of the Second Edition). The original reference for this drawing as noted by Pirenne is: Schultz (1866), Arch. mikr. Anat., 2, 175). Note the date of this reference!

The Title of Plate 6:

“The mosaic of rods and cones in various regions of the human retina, as seen under the microscope in fresh preparation”.

The figure reproduced here is one of three drawings in the plate and is labeled “Close to the yellow spot” (with others labeled “Periphery” and “At the ora serrata”).

This is a very important figure.

This is the distinct retinal motif that occurs at between eight and nine degrees of retinal eccentricity (as measured from the fovea) and is the point where the density of rods is first sufficient to completely surround each cone. This is the only point on the retina where this motif occurs.

An octagonal “eight rods around one cone” structure is seen.

Please note that the only geometric construction that can result in this symmetry is a ratio of 1.8:1 which is the actual ratio of sizes of cones to rods and which additionally corresponds to the visible band – 700-400 nanometers!

Thus it is the ratio of the sizes of the two types of retinal receptors that geometrically determines the width of the visible band.

It follows that the absolute size of individual receptors determines the wavelength range detected - it has been well documented that the ultraviolet vision birds have smaller receptors etc.

Now onto important matters.

From the Rosetta Stone diagram of the original paper reproduced below, the center-to-center distance between the cone and rod receptors geometrically determines the exact midpoint of the visible band of wavelengths. Please let this point sink in!

This point represents a geometrically-defined midband point from which all other wavelengths are referenced in determining the sensations that we term color (as Edwin Land brilliantly defined).

It also follows that two sizes of receptors  creating such a midband reference must be present on the retina for the sensation of color to be perceived.

It is seen then that geometry and electromagnetic wavelength are inexorably linked. It occurs to me that I am actually defining, what at longer wavelengths, is termed an “antenna”!

It follows that “optical wavelength antennas” exist – which returns to the point where this entire exercise began!

This light interaction on the retina at 8-9 degrees represents the peak of response to the middle (we term in shorthand “green”) the wavelengths that have been termed “primary”. This point (motif) is precisely “tuned” to this single wavelength with the density of octagonal structures leading to the claim that it is the peak of response.

Notes:

a.) The notation for the figure by Pirenne states that the referenced figure is taken “somewhere near the yellow spot”. The connotation of yellow is vague in the literature referring to the macula that may have something to do with the yellow lutein molecule present in the eye. I have proposed that formation of lutein in the eye may represent a “second line of defense” in preventing overexposure to light and damage to the retina.

b.) Crucial……as noted by Snyder (referenced in the original paper) the octagonal motif of the human retina seems to be characteristics of all species from crustaceans to honeybees. Meaning..??

GCH

11.10.09

Ojai,CA