What is a refractive error?
Light enters the eye through the cornea (the curved clear window of the eye) and is focused on the retina. Ideally, the cornea should be perfectly dome-shaped. When it is out-of-shape, light bends (refracts) at the wrong angle and images are not focused properly. This causes them to appear blurry or distorted. Problems with the focusing power of the eye are called refractive errors. There are three primary types of refractive errors: myopia, hyperopia, and astigmatism. In people with myopia (nearsightedness), the cornea is too curved, and items far away appear blurry. In those with hyperopia (farsightedness), the cornea is too flat, and items nearby and far away appear blurry. In people with astigmatism, the cornea is curved irregularly and items appear distorted. Spectacles and contact lenses are designed to compensate for visual imperfections – they bend the light before it enters the eye, helping the eye to focus.
