Removing red eyes is probably one of the first thing you'd do after taking a photo with your phone. Thanks to the default HTC One M8's photo editor, to Remove Red Eyes you just need to do as follows:
1. Use the default photo Gallery and open the picture you want to edit
2. Tap the Edit button
3. On the Effect tab, tap on the Touch Up option (You may swipe available effects to the left)
4. Now select the Red Eye Remove option and do the rest..