Human Eye Anatomy (was ion blue lights)

[Luis Marques <marques@rtis.ray.com>]

Marty Halvorson wrote:
> ...  There are 2 kinds, rods and cones, one is
> monochromatic, low light level sensitive, the others are divided into
> the three color sensitive types...
> 
> The density of the cells varies also.  The color sensitive cells are
> mostly near the center of the retina, the low light cells have a lower
> density, and are mostly near the edges of the retina.  That's why you
> can see low luminence objects (such as galaxies in the night sky) by
> averting your gaze.

All very true - it's been a while for me too.  The color cells are packed very
close together in the center of the eye and, besides seeing in color, see in
great resolution and detail, but are slow to react to motion and aren't as
sensitive in low-light conditions.  The Black/White low-light cells are
dispersed around the edges of the retina (peripheral vision) and are very
sensitive to motion, but can't distinghish fine details because they are so far
apart.  That's why a fluorescent light may not appear to flicker when staring
directly at it, but when you look elsewhere, you do get the sensation that the
lights are flickering.  The color cells still exhibit that shift in sensitivity
towards the green in low light conditions.

Mandatory Audi content: you can also get a faster reaction time by not staring
to the green light, but focusing your eyes just next to it.  The faster
peripheral vision will detect the change to green quicker.

Luis Marques