For a 15-year-old child, it is advisable to consult an ophthalmologist, preferably a pediatric eye specialist. The doctor can perform a thorough eye examination, determine the underlying cause of the concern, and advise whether any supplementation is necessary. Using supplements without medical supervision is not recommended, as children have specific nutritional requirements, and unnecessary use may not be beneficial and could potentially lead to unwanted effects. A proper diagnosis and guidance from a qualified specialist ensure safe and appropriate care.