If someone has been in darkness for 1-2 hours, and his eyes have fully adjusted to darkness, but then gets suddenly hit in the eyes by a bright light for about 10 seconds, would there be any retina problems?
Say a bright light about the intensity of a household lamp.
It’s my understanding that as we get adjusted to the dark, our eyes dilate resulting in our pupils expanding greatly. Once light is presented to a fully dilated eye, the pupil contracts to protect our retinas, pupillary response.
I’d be more worried about exposure to an artificially dilated eye from drops etc. that has a limited pupillary response, than one’s eyes that have just adjusted to darkness.
Your eyes adjust to darkness in three ways.
First, the pupils expand to let more light in. Your pupils also contract fairly quickly, so something like a household lamp isn’t bright enough to cause any permanent damage, even during the short time that the retinas are exposed while the pupils are contracting.
Second, the rods and cones (the light sensitive receptors) in your eyes produce photo-sensitive pigments which respond to very low levels of light. It takes the rods and cones something like half an hour to 45 minutes or so to fully regenerate all of these pigments, which get bleached out on exposure to bright light. So your household lamp will instantly wipe out these pigments, ruining your dark vision for the next half an hour or so. But no permanent damage.
Thirdly, the nerve cells in your retina become more sensitive in darkness, which is kinda like turning up the brightness adjustment in your eyes. Bright light will adjust the gain of these nerve cells very quickly, again wiping out your dark vision, but the nerve cells also recover again fairly quickly in darkness and this part of your dark vision will recover in a few seconds. Again, no permanent damage.
Your vision won’t be at optimal performance right away.
This should not cause any permanent damage. Tons of cavemen would have gone blind to lightning if so. I have had my eyes dilated to hell with a very bright light after sitting in a dark room. I see fine (well just as poorly as usual).