Let me know how that goes, seems like it would be damaging to your eyes.
It won't, it will be tiring but it will have no long-term effects on your eyes.Another name for this is "instantaneous recognition". It's used in some speed reading courses without turning the lights on and off (which WILL damage your eyes).
You take a card with a box cut out it, and read lists of words/numbers, pulling the card down the page as fast as you comfortably can. Eventually you'll be relying on the after-image and it will drastically increase your reading speed.
What you feel is your muscles adjusting to the amount of light, as if you are doing some physical exercise (sourcer.Oz about myths even doctors believe.)