Thank you for the additional information. It is very helpful.
The difference in pupil size is called anisocria. It is relative definition in terms of which one is the bad pupil -- is it the one that is too big, or the other one that is too small.
This distinction usually requires an ophthalmologist
or pediatric ophthalmologist's exam. Some kids naturally have different pupil sizes, but usually the differences are small and the same in both bright lights as well as dim lighting.
Another condition can be Horner's syndrome, which is blockage of the nerve pathway that controls the pupil size. This blockage causes the pupil to be smaller. It can also cause a ptosis
(droopy eyelid) on that same side as the smaller pupil. Sometimes this droopiness is very subtle.
I recommend your grandson be evaluated by an ophthalmologist or pediatric ophthalmologist for a complete eye exam. If it is a horner's syndrome, further testing is required to determine the location of the blockage and the cause.
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