Hello everyone,
I had a strange symptom this week. One pupil started enlarging and contracting but the other pupil did not change.

The pupil that was changing was on the side where I was injured (concussion). That eye now looks in a slightly different direction.

That moving pupil has been larger since my accident 2 years ago, but never like this. It looks darker too.

The night it was changing, I felt very dizzy. The next morning, the pupil acted like usual and I felt ok.

Wondering if this ever happened to anyone. Thanks!

It is very difficult to self-diagnose pupil size and reactions. If this has you concerned, an office visit with a doctor may be worthwhile. There are a few conditions that can cause this but a concussion is not one of the common long term causes. In other words, a concussion two years ago would not cause it now. One condition is Horner's Syndrome. It is rare and has a myriad of causes.

If you develop a building headache that gets intense, have somebody give you a ride to the emergency department at the hospital.
(edit) I forgot to include, this dangerous headache would also usually be accompanied by any form of speaking, smiling, or other muscle control losses.

For some, a mild version of this condition is ideopathic (cause unknown) and may have even existed prior to a suspected injury.

Dear Mark,
Your knowledge and helpfulness are a gift. I read your posts first and you are a blessing. I heard people should share our gift for free, and you do.

Your advice calms probably more than a visit to the doctor who probably doesn't have pcs and you know we thank you! When my head hurts every time I drive over a speedbump I think of your advice.

I saw neurologists and my pupils are different sizes by millimeters. Will google Horners.