Recently I got my Samsung Galaxy Note 3 and noticed an Samsung Eye icon which would become active at some point and then become inactive. I was wondering what it was and then I found out that this is basically the Camera of Galaxy tracking your eyes and face movement.
There are a lot of features in Galaxy S4 and Galaxy Note 3 (and probably a lot others) by Samsung. For example the video will pause if you look away from your device or if you are reading, the section where you focus will automatically zoom in etc. When the feature is in use, the Eye icon will become active and will become inactive once the feature is not in use.
If your Eye icon remains active all the time, please take out your battery and turn on the phone again. This will fix the problem.