Light Circle Around Pupil

You may be referring to an "arcus senilis." An arcus is a ring of lipid (fat) or calcium deposition in the periphery of the cornea. This may be perfectly normal and occurs with aging (thus the name—senile arc, or age associated ring around the cornea). The arcus may occur pathologically in younger people in the setting of high cholesterol. So, if you are referring to a ring that occurs at the junction of the white part of the eye (sclera) and the iris (the colored part of the eye) in an older person, it is probably normal. If the person with the ring is younger, it might be a sign of increased cholesterol. Consider being seen by an ophthalmologist to determine if the "light circle" you are referring to is a sign of a systemic issue that might need further evaluation.