From Brotato Wiki
Alien Eyes is an in-game item that can be bought from Shop or can be found in a Crate. Most Items increase the Stats of the player while some of them provide unique effects.
Alien Eyes' projectiles can Crit, Lifesteal, pierce, bounce do "normal" attack things. However, it does not work with Scared Sausage
The damage scale with your Max HP and your % Damage
Each additional Alien Eyes increases the amount of projectiles fired by +6.