It shouldn't be, as long as your eyes water themselves enough and you're not straining on something overly bright. You'll go into retnal fatigue after a couple of minutes, which causes mild hallucinations. You'll also get roving black spots as your receptors have enough and shut off to purge, which is a concentration in itself to mentally correct for to avoid visual distortion. Yes, it can be done. The mind naturally tries to fill in the blanks anyway. So, its a matter of sufficient focus on the image to override the parts of your eyes that shut off so as to keep the image.
Under moderate lighting, I don't believe this should cause any actual damage that a minute of blinking won't correct. But then again, I'm not a doctor, so don't listen to me |