Cone cell: Difference between revisions

Revision as of 12:32, 16 July 2006

Revision as of 18:56, 22 August 2006

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==Structure==

Cone cells are larger and less numerous than rods. Structurally, cone cells have a [[cone (solidgeometry)|cone]]-like shape at one end where the pigment that filters incoming light, giving them their different response curves. They are typically 50 [[micrometre|µm]] long, and their diameter varies from 1.0 to 4.0 µm, being smallest and most tightly packed at the center of the eye at the [[fovea]]. The blue-sensitive cells are a little larger than the others.

[[Photobleaching]] can be used to determine cone arrangement. This is done by exposing dark-adapted retina to a certain wavelength of light that paralyzes the particular type of cone sensitive to that wavelength for up to thirty minutes from being able to dark-adapt making it appear white in contrast to the grey dark-adapted cones when a picture of the retina is taken. The results illustrate that '''S''' cones are randomly placed and appear much less frequently than the '''M''' and '''L''' cones. The ratio of '''M''' and '''L''' cones varies greatly among different people with regular vision.<ref>Roorda, A. and Williams, D.R. (1999). The arrangement of the three cone classes in the living human eye. ''Nature, 397,'' 520-522.</ref>