Temporary blindness what is it?

ok so i was working on my hw on the computer for a while and i stood up to give my dad a hug cause he just got home from work and i got really dizzy and i lost my balance a little and was temporarily not able to see for like 5-10 seconds and my face felt really warm. what causes this? it is because i was staring at the computer for a while or is there like a physical problem with me?