Myopia is a refractive error that affects the eyes. It is commonly known as nearsightedness. People with myopia have difficulty seeing distant objects clearly but can see nearby objects clearly. This condition occurs when the eyeball is too long or the cornea is too curved, causing light to focus in front of the retina instead of on it. It is important to note that myopia is not a disease but a common vision problem. It can be corrected with eyeglasses, contact lenses, or refractive surgery. Therefore, option 4, "Eyes," is the correct answer.