This document defines refractive errors and discusses their causes, types, and management. Refractive errors occur when the shape of the eye prevents light from properly focusing on the retina, causing blurred vision. The main types are myopia, hyperopia, astigmatism, and presbyopia. Myopia is near-sightedness caused by the eyeball being too long, while hyperopia is far-sightedness caused by the eyeball being too short. Astigmatism results from an irregularly shaped cornea. Presbyopia is age-related and due to stiffening of the lens. Management involves correcting refractive errors with appropriate eyeglasses or contact lenses, or refractive surgery in some cases. Eye exams are