What are the three common refractive defects of vision mentioned in the paragraph, and how are they named?

The three common refractive defects of vision are myopia, hyperopia, and astigmatism. Myopia, or nearsightedness, occurs when distant objects appear blurred as light focuses in front of the retina. Hyperopia, or farsightedness, results in difficulty focusing on close objects, as light converges behind the retina. Astigmatism arises from an uneven cornea or lens curvature, causing distorted or blurred vision at various distances. These conditions are named based on how they affect the refraction of light entering the eye, leading to visual impairments. Corrective lenses, such as glasses or contact lenses, are commonly used to address these refractive errors.