Myopia is a refractive error that causes nearsightedness and blurred vision when looking at a distance. The condition is very common, affecting approximately 30 percent of the total U.S. population. The condition usually develops in childhood and gradually worsens throughout adolescence. In some cases, people develop myopia after Myopia is easily diagnosed with a comprehensive eye exam and corrected with various treatments, including glasses, contact lenses or refractive surgery.