I've used F.Lux for a bit as part of my sleep cycle; but had to stop. It gave me intense headaches and really really strained my eyes. In the end my optician ad

I've used F.Lux for a bit as part of my sleep cycle; but had to stop. It gave me intense headaches and really really strained my eyes. In the end my optician advised me to stop using it. YMMV of course but do take care :)