The size of iris is related to the stimulation of light.
There is a medicine called mydriatic medicine. I once used an eye drop for use at night. This medicine is used before going to bed.
Once again, I was going to sleep during the day and used this eye drop. I have to go out because of something. I can't open my eyes outside, the light is too dazzling.
When looking in the mirror, the pupil is particularly dark and the iris has spread. I have to find a place to sleep
Therefore, it is very convenient to enlarge the pupil, and it is also possible to apply eye drops to the ground, but the light can't be seen.
It's natural to be beautiful.