Just noticed my left eye is really red. no pain, no itching, no pus, no vision loss. just red. on computer for 4 hours straight. is that the cause?

Bleed: Sounds like a sub-conjunctival hemorrhage. As long as the vision is unchanged and there is no pain, everything should be fine. If it is a little irritated, then you can use an artificial tear up to 4 times a day to lubricate. This is due to a blood vessel leaking blood and is usually without cause. Sometimes straining or blood thinner can cause this. If it continues to happen, follow up!