The ability to see is based upon the way our eyes bend, or refract, light. Light rays enter the eye through the cornea and then pass through the lens to be projected onto the retina (the light sensitive layer in the back of the eye). The light rays that are projected onto the retina create an image which is sent to the brain via the optic nerve, allowing us to see. In an eye with perfect optics, the focus is precise and the image projected onto the retina is sharp. However, if there are imperfections in the eye the light rays are bent in a way that results in a blurred image being projected onto the retina. Refractive errors are a result of these optical imperfections that prevent the eye from properly focusing light, causing blurred vision. Common refractive errors are nearsightedness (myopia), farsightedness (hyperopia) and astigmatism (distorted vision). Laser vision correction is often utilized to correct all three types of refractive errors.