Red-eye is caused by the flash from the camera reflecting off the retina and lighting up the blood vessels inside the eye.  And, because most times when a flash is used, the subject is in low light conditions and their pupils are already dilated, causing more of the flash to enter the eye.

There are several ways to prevent red-eye:

• Red-eye reduction feature – some cameras have this feature; the flash goes off twice, once right before the picture is taken to cause the pupil to contract, reducing red-eye significantly and then again when the picture is actually taken.
• Turn on the lights – turning on all the lights in the room can also have the same effect; the pupil is contracted, therefore less light from the flash can enter.
• Look away – have your subject look towards the side of your camera, not directly at the flash.  By looking slightly away from the flash, the effects of red eye can sometimes be minimized.
• Detach the flash – the best way to eliminate red eye is to use a detached flash and hold it several feet away from the lens or bounce the flash off the ceiling.  So, if you are ambitious, consider getting an external flash.  However, for most of us taking pictures, this is not really a realistic option.

And, the good news is, if you can’t prevent it, you can correct it after the fact when using a digital camera:

• From the camera – most digital cameras have the option to correct red-eye directly on the camera using the cameras menu.  Since all cameras are different, check your owner’s manual instructions.   Check out this site to download manuals for many different camera models.
• After pics are downloaded – most image programs such as Photoshop and Picasa can easily remove red eye.  Try these sites for step-by-step instructions for removing red-eye with Photoshop and Picassa.