What is a Refractive Error?

Normally, rays of light entering the eye are brought to a precise focus on the retina – the light sensitive layer lining the back of the eye. When such a focus is not achieved, a refractive error results and vision is not clear. These imperfections in the focusing power of the eye are called refractive errors. The common refractive errors are:

• Myopia, or Nearsightedness;
• Hyperopia, or Farsightedness;
• Astigmatism

Myopia: A myopic eye is longer than normal or has a cornea that is too steep, so that the light rays focus in front of the retina. Close objects look clear, but distant objects appear blurred.

Hyperopia (Farsightedness): Hyperopia is aterm used to describe the condition of farsighted . The causes of hyperopia are typically genetic and involve an eye that is too short or a cornea ie too flat,so that images focus at a point behind the Retina. People with hyperopia can usually see distant objects well, but have trouble focussing on nearby objects.

Astigmatism (Distorted vision): ASTIGMATISM (cylindrical error) occurs when incoming light rays unable to reach a common focus within the eye. Astigmatism distorts or blurs vision for both near and far objects. The cornea is the clear front window of the eye. A normal cornea is round and smooth, like a basketball. When you have astigmatism, the cornea curves more in one direction than in the other, like a football. It is possible to have astigmatism in combination with myopia or hyperopia.

courtesy : Allergan ; Eye Calender