5. Horner Syndrome

Caused by a disruption in the nerve pathways that travel from the brain to the face and eyes, Horner syndrome usually develops as a result of other health issues like stroke, tumors, or spinal cord injury. According to LiveStrong, it is “a triad of symptoms caused by impairment of specific fibers in the third cranial nerve that innervate the eye and face.”

Other symptoms that could develop as a result of Horner syndrome include a droopy eyelid, smaller pupil size, and less sweating on the affected side of the face. LiveStrong stresses that this condition is most likely to cause an eye color change in children less than a year old, but it may also occur in adults on rare occasions.