Nearly all photo editing software have ‘fix red eye’ option including Windows Paint, Adobe Photoshop, Adobe Lightroom, iPhoto, Photoshop Elements, Gimp. Many of these are free software you can download from the internet. Make a copy of your picture before you start so that even if something goes wrong you have a backup. Select the red eye option and mark the eyes. Draw a circle around the iris to mark its outline and the software will detect the effect. The effect will be fixed and you will have natural pictures.
Online photo editing sites also offer the same service. Since red eye effect is a very common problem with photographs, nearly all such sites have the option. All you have to do is to upload your photo and the red eye will be fixed.
If you have printed photographs with the eye effect, you can still fix them. Buy an anti-red eye pen from a digital shop that provides cameras and other parts. This special pen can be used to coat over the iris, changing its color. The pen is specifically made for this purpose and will fix your photographs easily. If you do not want to use the pen, you can scan your photograph and upload it to your computer. From there you can use the above two steps to fix the effect like digital photographs.
If you are still unsure of how to fix the effect and fear that you might mess up your photograph during the process, take it to a photo editing shop. The professionals there will fix it in no time and will give you back normal copies.