Lyn saw the ophthalmologist today. Lyn's pupils are currently have a 1 millimeter difference. The doctor took nearly an hour working with Lyn and would like to see her again in a week to see if there is any change. He was able to rule out a number of things but didn't find a definitive cause. He's diagnosed her with anisocoria which is just pupils of unequal sizes.
It turns out aniscocoria is fairly common. It can be completely benign or something which is symptomatic of bigger issues. The concern is that this has only just been noticed in Lyn and has never been noticed before.
So, we'll keep observing her. If anything changes between now and next week's appointment, she'll be seen immediately.