Your iOS device had been designed and manufactured for daytime use actually. For this reason when you start using your iDevice at night or in a dark environment, you feel you get blinded by your iDevice’s screen. Thing drives to this reflex is blue light which is also very harmful for your eyes, and can causes sleep disorders.
Unblue is the very first app minimises effects of blue light on the App Store which helps you to protect your eyes while browsing the Web and prevents sleep disorders.