The eye icon comes from the function Smart-Stay which is implemented at the Samsung Galaxy S5. Smart Stay is a function which can illuminate the display as long as you look at it.
Go to Menu -> Settings -> Display In this sub-menu of your Samsung Galaxy S5 you will find an option called "Stay Smart". Remove the check mark and then the function will be disabled on your Samsung Galaxy S5. The eye icon will not appear anymore at your status bar.
Source : http://www.solvemix.com/index.php/android-smartphones/79-samsung-galaxy-s5-eye-icon-in-status-bar