In order for our eyes to be able to see, light rays must be bent or "refracted." Light rays pass through the cornea and are focused by the lens on the retina, the nerve layer that lines the back of the eye.
A refractive error means that the shape of the eye doesn't refract the light properly.
- Myopia: A myopic or nearsighted eye is longer than normal, so the light rays focus in front of the retina. Close objects look clear, but distant objects appear blurred.
- Astigmatism: A normal cornea is round and smooth, like a basketball. With astigmatism, the cornea curves more in one direction than in the other, like a football.
- Hyperopia: A hyperopic or farsighted eye is too short for images to focus on the retina, so close objects appear blurry.