Dear 100 Hour Board,
I just spent about an hour reading outside. It was pretty sunny out, and the white pages of my book were really bright. So, I kept my right eye closed and squinted with my left eye while reading. When I came back inside and opened both eyes, my brain couldn't seem to reconcile the information between my eyes, and everything looked off. By closing one eye at a time, I figured out that my left eye (the one I'd been using outside) was now giving everything a reddish tint, while my right eye seemed to be giving everything a bluish tint. Why do you think this is? I don't need medical advice -- I'm just curious.
- Rose-Colored Monocle
Dear Monocled Rose,
I bet it's the same reason that, when you look at lightbulbs a certain way they are tinged either red or blue on both sides. It's something I noticed during sacrament meetings a very long time ago. I wasn't always the most attentive lad, and I spent many long minutes staring upwards. Eventually I noticed that, when looking at a lightbulb while looking up so that the lightbulb appears near the top of your vision, a red tinge appeared around the top of the light, and a blue tinge appeared around the bottom. The same effect occurs when looking downwards at a light, except blue appears around the top and red appears around the bottom.
This is an artist's rendition of the occurrence. They are not eggs.
I've never known why this occurs, but it sounds like a similar thing. It probably has something to do with blood vessels in your eyes being strained or something like that.
Reading outside is one of life's great pleasures. I hope it was a good book!
The occurrence you describe happens to be a fairly prevalent phenomenon; some people even claim that their vision is always slightly red-tinted with one eye and slightly blue- or green-tinted with another. The most common explanation is that the filtered light affects the cone cells in your eyes. Our eyes have cones that detect red, green, and blue light. When your eyelid is closed, you're effectively putting a red-tinted screen over your eye (since your flesh is pink, it blocks out more blue- and green-wavelengths, much like amber-colored sunglasses do). When this is sustained long enough, your red-detecting cones become tired. Your blue- and green-detecting cones are then better at receiving light, so your vision becomes momentarily bluish/greenish in your right eye. This also explains optical illusions that require you to look at an image with colors for a while and then look at a white space; this causes the retinal fatigue explained above and gives the complementary-color effect when your eyes attempt to white-balance. Those that have always had the problem of two different tints most likely have a different distribution of these cones in each eye, but it can also be caused by other factors like pupil size—which actually may have factored into your situation as well, since our pupils dilate in the sun.
Your other eye probably had the other effect because sunlight naturally is more blue than incandescent lights, so if that's the kind of light you returned to, your blue-detecting cones in your left eye could be fatigued and you were better able to see red out of that eye. It could also be caused simply from your brain trying to understand the contrast with the all-blue vision from the other eye.
So, basically, it was retinal fatigue, and I'd suggest wearing sunglasses in the future.