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The causes of small pupil include side effect of medications, aging effect on the iris
dilator muscle, damage to iris dilator nerves/muscles, over action of iris constricting nerves/muscles, horner's syndrome due to damage to the sympathetic nerve (usually this tend to affect one eye, so unlikely in this case). It is likely that you may be experiencing the effect from either medication side effect, normal variation of small pupil, or effect of aging on pupil size. I suggest that you follow-up with your eye doctor for closer evaluation to exclude any abnormal eye nerve problem. In the meantime, you should not be concerned, as it does not affect your vision, but follow-up with your eye doctor for closer evaluation..
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