…sitting in a dark room staring at a computer screen?
Why would you?
Depeds. Are both hands on the keyboard and/or mouse? 
Yes.
Most of the time.
I ask because I have been told for a millennia not to watch TV in a dark room because it would hurt my eyes, and a computer monitor is not much different than a tv.
My eye sight isn’t what it used to be but I don’t know if it’s because of the dark room effect or the fact the I’m creeping closer to senility.
Depends on what’s ON the monitor.
Air Traffic controllers working in a TRACON facility do something similar and they don’t go blind. They do have unusually high rates of substance abuse and depression though. If you aren’t getting paid for it, it is best to find a friend and get out of the house once in a while. There are more immediate issues than blindness with sitting in a dark room looking at a computer screen all day. If you find yourself doing Google searches for pants with an elastic waist-band, it is time to try something new.
A man went to the doctor complaining about a problem with his penis. The doctor told him to strip down and immediately noticed his bright orange member. “Oh my God!” the doctor said. “I have never seen a case like this. Do you work with any exotic chemicals?”. “No, the man replied. I am unemployed and have been for years.” The doctor asked, “Well what do you do all day?”.
The man replied. “Not much, I mainly eat Cheetos and surf the internet for porn.”