The "Red Eye Reduction" function provides you with the ability to change a single pair of red eyes at a time. If the mask of Iris doesn't fit very well, the red eye can not be reduced completely.

If you want to remove the red eyes for every subject in the image, you will need to export an repeat the procedure for every set of red eyes you wish to get rid of. Keep in mind that this procedure may degrade the quality of the image eventually.