THOUGHTS AT THE NEW YEAR – THE INTRODUCTION OF MODERN PHYSICS INTO VISION SCIENCE

by Gerald Huth on December 31, 2010

I was recently admonished to the point that “if I had only learned biology I would understand the vision process…” The heartening news in this comment is that the writer was somehow motivated to write a rather lengthy tome quoting book and verse advising me in some detail where I had gone astray. Another comment, again in a lengthy exposition indicating that he/she had really looked at the work, summed up my explanation as  “weird” ( I detest the use of this word  that is often used to describe the perceived mystery of  quantum physics. Its’ use in my view has the profound effect of closing off further thought).

I would propose that what is necessary in contemporary vision science is the introduction of  the findings of modern physics.  I  herewith cite two modest examples. (there are many more!):

1.) I have discussed  the body of work that analytically treats  the receptors of the retina as optical waveguides (as in “fiber optic lightguides”). It is not my intent to disparage this work that dates from the 1960’s and 1970s’  but only to point out that there are recent experimental results that drastically alter the conclusions.  Specifically, it was thought at the time that light was conducted within the body of such a light guide. It has been found, however, in the last few years (referenced in the body of the work) that when the diameter of such a fiber is reduced to the near field of light ( to dimensions approximating light wavelength or the diameter of retinal receptors)  light is actually conducted outside of (or around) the body of the fiber optic  light guide. I note  that this result fundamentally supports my optical antenna explanation – light interacts as a wave  outside of or between adjacent retinal receptors.

I would note that these waveguide analyses fundamentally assume that light travels through the body of a receptor as a wave.  But then…..this wave nature of light somehow translates to a particle (the photon) at each point along the length of the  guide in  interaction with the thylakoid stack of  retinal pigments. This represent the physics conundrum of the wave/particle duality.  Light is first proposed to travel as a wave but then interacts (with pigment molecules) as a particle !  Are not these considerations really problematic in this type of analysis ?

This modern antenna explanation provides an answer – the eye did evolve to detect light as a wave in interreceptor spaces with the absorbed energy translated at each detection site on the retinal surface  into a quantized (electron) particle.

2.) The second example of microspectrophotometric  (MSP) measurements of individual retinal receptors again made in the 1970’s and early 80’s  is more serious. There are many problems with these measurements as I have discussed on a number of occasions.

Specifically, such measurements were very difficult to make balancing the need to obtain intelligible signals from sample exhibiting very low optical absorption values  (a mean transverse absorbance of ~0.03) and encompassing very small sample areas. Since it was not possible to collimate interrogating light to the axial (i.e., end on) micron dimensions of retinal receptors the measurements were made along the transverse length of “layed out” individual dead receptors.

In my review of MSP measurements, papers consistently do not address the actual dimensions the light beam that is interrogating the receptor section – which they probably could not measure. One gets the idea that this bean had the dimensionality of a slit that would have been necessary to obtain readable signals.

(I would note that in the context of my explanation, this type of measurement fails on two counts. Light is absorbed in the dimension between two adjacent receptors with this dimension being precisely defined only the living state of the organ).

Any such measurement scanning an optical beam across the three refractive indices of water (?), then across the micron width of a receptor  and  again back to water would yield some finite absorption value!

A more serious objection – investigators at the time (and until now!) assumed, following the finding of the trichromicity of vision,  that they were measuring individual receptors that constituted three “classes of cones” .

I will reference as an example of such measurements a paper (but there are many) by Bowmaker and Dartnell “VISUAL PIGMENTS OF RODS AND CONES IN A HUMAN RETINA”,J. Physiol. (1980), 298, pp. 501-511.

Quoted from their SUMMARY of this paper:

“Three classes of cones were identified. The long-wave cones (‘red’ cones) had a lambda max of 562-8 + 4-7 nm (n = 19) with a mean transverse absorbance of 0-027 + 0 005. The middle-wave cones (‘green’ cones) had a lambda max of 533-8 + 3-7 nm (n = 11) with a mean transverse absorbance of 0*032 + 0 007. The short-wave cones (‘blue’ cones) had a lambda max of 420-3 + 4-7 nm (n = 3) with a mean transverse absorbance of 0 037” (Underline is mine.)

The MSP curves of the response of the hypothetical three types of cones presented in their Figure 1 should have always, in my view, been viewed as suspect ! The blue and green sensitive curves are hardly differentiable.

BUT…these seem to be the values that have been picked up and used in every text on vision. (See these curves in my comment on the Fallacious Nature of the Tetrachromacy of Vision).

MORE TO COME…..…

GCH

Ojai, CA

12.31.10

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