Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A refractive error is an eye disorder characterized by the inability of the eye to clearly focus the image. This defect leads to blurred vision or vision impairments and may cause blindness. While myopia, also known as nearsightedness, makes it difficult to see distant objects clearly, the eyes of individuals affected by hyperopia (farsightedness) cannot focus on close objects. An irregularly curved cornea leads to refractive errors in people with astigmatism. Learn more about disorders of refraction as well as their causes, symptoms and treatments in this book.