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No, stroke is unlikely but there could be some pathology of either the optic nerve of the left eye or some retinal pathology. She needs to get a dilated fundus examination to reach a diagnosis. You will have to take her to an ophthalmologist for that. Sometimes, difference in pupil size could be physiological as well meaning without any disease. This condition is known as anisocoria. If it is pathological, then it is likely that she has reduced vision with her left eye. You can check that. Thanks.
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