Edit: My thought process is that using one eye would still cause enough uncomfortable sensations that closing / squinting both eyes is the only viable option but apparently not. One eye is completely normal and painless.
This happened to me when I was driving the other day and I was worried I’d have to pull over on the highway, but when I closed one eye I was able to see with no pain sensation whatsoever with roughly the same amount of light radiation entering my 👁.
I know it’s technically less light for my brain to process, less intense on the nerve signals firing but I couldn’t intuitively get to the bottom of this because the common person might assume having one eye open could be worse?
In: Physics
The optical nerves that links each eye to the brain forms an “X” because the left eye’s nerve connects to the right side of the brain and vice versa.
When both eyes see bright light, a lot of signal goes through the nerves and it takes a few seconds for our eyes to adjust to send less signal. These signals meet at the center of the “X” where the nerves cross over, called the optic chiasm. Too much nerve signal in one region can be interpreted as pain by the brain.
Closing one eye helps reduce the overall amount of signal below a pain-causing level as our eyes adjust to the bright surroundings.
Compressive lesions on this optic chiasm can cause photophobia (sensitivity to light) because it’s worsening the “traffic jam” of nerve signals: https://pubmed.ncbi.nlm.nih.gov/11937897/
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