When using a flash to take pictures, there is always a possibility that the flash may reflect back from the retina of the eye to the camera and film yielding subjects with "red" eyes.
To eliminate or to reduce the frequency of this taking place when you take photographs with a flash, keep room lights bright and have the subject avoid looking directly into your camera. Using a flash extender or a detachable flash will also help avoid "red" eye by allowing the flash to be placed further from the lens of the camera.
Note: There are "Red Eye" correction pens available through many photo outlets with which the user may touch up the eyes thereby eliminating the "red eyes" from the prints.
When using a flash to take pictures, there is always a possibility that the flash may reflect back from the retina of the eye to the camera and film yielding subjects with "red" eyes.