When I was still in elementary school, i found if i shake my hand in front of a old school CRT display, there are many shades of my hand around my actual hand. Beside of that, it also strain my eyes quickly.
Nowadays this effect also appear on some modern LED displays, because the usage of low frequency PWM backlight.
Once this effect is observed on certain LED light, be aware of that light can strain your eye.
Sometimes you can get rid of this effect by overclocking the PWM.