Red eye is caused by the flash on the camera. The light leaves the flash, goes towards the subject and reflects off of the retina of the eyeballs. This retina just happens to be red. So now when the shutter opens, it?s got two glowing red eyes before it.
I prefer the following technique over many other techniques;[list][*] fast[*] simple[*] good results[/list:u]
Technique[list][*]zoom in on one of the eyes.[*]use the Elliptical Marquee tool and hold down ALT + Shift and create a circular selection starting in the center of the eye and stop just outside to red area. (You may need to use the move tool afterwards to center the selection)
ALT: the selection will draw outwards from the starting point
SHIFT: will create a perfect circle[*]go to
Select / Feather? and enter a value of
1[*]go to
Image / Adjustments / Channel mixer?[*] select:
Output Channel :
Red (very important)
Source Channel Red :
0 %
Source Channel Green:
50%
Source Channel Blue :
50%
What I?ve done is that I dropped the Red channel with 100% and compensated with 50% in both the green and blue channel. If necessary you can also select the option
monochrome.[/list:u]More of this technique is explained in this Quick Time movie:
http://www.apple.com/creative/resour...624redout.html 
Red eye removal 
Linear Mode
