I'm not sure for the circumstances you describe that a slight blurring/difficulty focusing, is to do with a condition that eye drops/artificial tears can help. I think the root cause may be more neurological than an external factor for eyes. People with migraine headaches have trouble focusing and suffer vision difficulties. I think it may be tied in with this. Long nights/headaches/hangover/'stuffiness' from too much time on a computer- I think it more likely to be a deeper cause in the brain. What do you think?