This small pupil could be because the visual processing can struggle with too much light so the pupils constrict to reduce the light entering the eye. This is different than the dilation issue that indicates severe brain damage. In that case, the control over the dilation process is disrupted. A difference between how each eye dilates would indicate a severe brain injury.

I have needed to wear photo sensitive lenses since the 70s. I also wear a brimmed hat to reduce brightness from the sun or lights. This is not uncommon.

Older ballast fluorescent lights can be problematic due to the frequency of the flicker. Newer electronic ballast lights are usually less of a problem.