Talk:Retina

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Contents 1 Artificial vision research 2 Perception of red blood cells 3 Photoreceptors vs. Retinal ganglion cells 4 Physical Structure

[edit] Artificial vision research

Has anyone tried to sample the actual signal sent through the optic nerve? I assume it's electro-chemical, and so should be detectable by picking up EM radiation at the surface of the nerve. This might give a clue as to what kind of signal the brain requires to create vision. It could also eventually permit sharp, detailed, artificial vision. If this note is outside the scope of this discussion, feel free to delete it. - LarryH 01:09, 15 Nov 2003

I'd be intrested in this too, but from a bit different perspective: Could the eye be potentially used as an digital camera as it seems it transforms light(the image) to electrical(and chemical) signals(to the nerves/brain). If we could somehow intercept these signals, and interface them with computer then with some processing it should produce an digital image? I think this should be quite easier then artificial vision, as the processing could be done offline, and the signal going to brain would be unaffected. 84.248.191.188 17:59, 6 January 2007 (UTC)

[edit] Perception of red blood cells

Can someone cite a reference for the phrase The red blood cells in the capillaries in front of the photoreceptors can be perceived as tiny moving dots when looking into blue light (the colour best absorbed by those cells).? I don't have any reason to believe it isn't true; I just want to read more about it, as the phenomenon fascinates me whenever it happens to me. - mjb 08:40, 30 Mar 2005 (UTC)

In the science museum of Minnesota in Saint Paul, there's an exhibition where they make you look into blue light so that the moving dots really stand out, and one can notice the coordination of their movement with the heartbeat. That's where I got the red-blood-cell explanation from; I don't have a written reference. However, I just found this link which claims that it's called "Scheerer's phenomenon" and that it's actually due to white blood cells in the capillaries rather than red blood cells. Cheers, AxelBoldt 22:25, 30 Mar 2005 (UTC)

I just emailed the science museum to see if they have a reference. AxelBoldt 00:27, 31 Mar 2005 (UTC)

Well, the science museum did not write back, but I found another reference that explains the effect as caused by white blood cells. They call it "entopic phenomenon" but that is not the correct term; "entoptic" (not "entopic") means "related to the appearance of the inner structures of the eye". And the original reference seems to be

Scheerer R., Die entoptische Sichtbarkeit der Blutbewegungen im Auge und ihre klinische Bedeutung. Klinisches Monatsblatt Augenheilkunde 1924;73:67-107

and the explanation is given here:

Sinclair et al. "Investigation of the source of the blue field entoptic phenomenon.", Invest Ophthalmol Vis Sci. 1989 Apr;30(4):668-673

I'll change the article. AxelBoldt 22:26, 6 Apr 2005 (UTC)

[edit] Photoreceptors vs. Retinal ganglion cells

In the introduction: "The retina contains photoreceptor cells (mainly rods and cones, but also some retinal ganglion cells) which receive the light". I don't think it is appropriate to mention Photosensitive Ganglion Cells in the intro, since they are not even mentioned in the main text. As is it is confusing because it looks like retinal ganglion cells are photoreceptors, which is not the case for the vast majority of them. So I modified the sentence. In the Physiology section, I added that X and Y ganglion cells (in the cat) and M and P ganglion cells (in primates) were not in perfect correspondence. The Physiology section needs some more cleaning. Gaelle Desbordes 02:09, 14 September 2005 (UTC)

[edit] Physical Structure

I found these two lines to be confusing:

• As a byproduct of evolution, the ganglion cells lie innermost in the retina while the photoreceptive cells lie outermost. Because of this arrangement, light must first pass through the thickness of the retina before reaching the rods and cones.

To me this sounds like Light first hits the ganglion cells, then the amacrine/bipolar cells, then the horizontal cells, and finally the photoreceptors. Paskari 13:41, 3 April 2007 (UTC)