No matter what you stare in a long time, bad effects on eye sight must happen. So staring at anything for too long wouldn't be a good idea. But seriously, you have gotten eye fatigue and one eye twitches uncontrollably by playing 15+ hours on the computer. You also will suffer an occasional headache, etc. The old CRT's emitted radiation that was suspected to help cause eyesight problems in people with long term exposure. But mostly eye problems come from not exercising them enough, and staring at one focal point for many hours a day can cause that. So there is nothing to do but stay away old computer monitors and TV screen. But not get far away from then forever, you still can play them for a while. If you feel tired and fatigue, you can drink a cup of tea and eat some fruits. Also, you can place cucumber slices on eyes to reduce fatigue.
I never heard this kind of saying before. Nowadays people are spending more than 8 hours per day in front of a computer, staring at the monitor. It is very likely to have eye strain for doing so. You can update the monitor because the old CTR monitor has a very obvious flicker of images, which is the main cause of eye strain. The higher resolution of the monitor, the larger the monitor is, it is better. The size of monitor be at least 19 inches. Adjust the brightness and contrast and take frequent breaks, which can help allay the eye strain obviously. Blinking can help moisten the eyes. When staring at the monitor, people tend to blink five times less than usual, which leads to excessive tear evaporation. Blinking can help spread the tear film evenly on eyeball to effectively lubricate eyes.