[John Chapman (OP)]

Can anybody tell me why, after a bright light is shone into your eyes, you then see a dark purple blotch floating in front of your vision for several minutes?

Also, if you blink or close your eyes at this stage the blob will instantly turn bright green while your eyes are closed and back to purple once they are open again. Why is that?

[Chemistry4me]

Intense light, such as from a flashbulb or uncovered light bulb, can stimulate the retina (the light-sensitive tissue at the back of the eye) to its maximum response. When this occurs, it takes awhile for the retina to "recover." For a short time you are not able to see well, or you may see spots or a dark afterimage.

http://www.uic.edu/com/eye/LearningAboutVision/EyeFacts/FYIAboutEyes.shtml

[John Chapman (OP)]

Any idea why the colour of the spots go from red to green when you close your eyes?

Can anybody else confirm that this happens with them?

[Chemistry4me]

It happens to me but I don't know about the spots changing colours.
Usually when I've been outside for 10-15 min and it is really bright, when I come back inside, I see all kinds of funny colours [] and dancing movements.

[John Chapman (OP)]

Ahhh. That's not quite what I am talking about. When indoors look into a bright torch for just a few seconds. Switch off the torch and look at a (preferably) white wall or ceiling. Voila! One red blob! Now close your eyes for a couple of seconds. Open them. Close them again. Stand on one leg. And you should notice the blob changing from red to green each time your eyes close. If you fall over it's because you believed me about standing on one leg!

I'm beginning to think that my eyes are unique. Or possibly just weird.

[Chemistry4me]

Does this happen to you often?

[John Chapman (OP)]

What. Falling over?

[John Chapman (OP)]

Only on a Friday night!

[Chemistry4me]

Well, your eyes don't forget what they see immediately.

I still think it is this

Intense light, such as from a flashbulb or uncovered light bulb, can stimulate the retina (the light-sensitive tissue at the back of the eye) to its maximum response. When this occurs, it takes awhile for the retina to "recover." For a short time you are not able to see well, or you may see spots or a dark afterimage.

http://www.uic.edu/com/eye/LearningAboutVision/EyeFacts/FYIAboutEyes.shtml

[Chemistry4me]

Do you wear glasses or contacts?

[John Chapman (OP)]

Quick. Someone come and rescue me. Chem4me is making me think I'm a freak. Surely someone has experienced this colour change phenominum. Anybody??

[Chemistry4me]

I recall seeing purple colours, do you?

[John Chapman (OP)]

Do you wear glasses or contacts?

I'm a little short sighted and I've had reading glasses fir the last 18 months or so. But I've experienced this phenomenon for as long as I can remember. And I'm sure I once heard it talked about on a 'fascinating facts' radio program many years ago.

[John Chapman (OP)]

I recall seeing purple colours, do you?

Do they remain purple when you close your eyes?

[Chemistry4me]

Lemme try...[]

[Chemistry4me]

DOH! The torch isn't working!
Sorry, even bringing my head really close to the lightbulb doesn't do it []
I'll have a go (maybe) when the Sun is out []

[Chemistry4me]

you then see a dark purple blotch floating in front of your vision for several minutes?

Several minutes?
Must say that that's never happened to me. Never lasts more than 30-60 seconds.

[John Chapman (OP)]

Yes, I think several minutes is an exaggeration. It just shows what a drama queen I can be. The colour change isn't, though. That happens every time.

Looking at the sun would work really well for me. But be careful, if you try.

[Chemistry4me]

After being out in the Sun and coming inside, if I shut my eyes really hard I can see spots.

[Chemistry4me]

Does this happen to you sometimes when you go to sleep? Maybe right after you turn the light off? Because it sometimes does to me!