Anatomy of the Eye
Refractive Errors Explained
A Normal Eye
When light rays enter the normal eye, they are focused at a single point on the retina, located at the back of the eye. The cornea (the clear portion at the front of the eye) and the lens inside the eye bend or 'refract' the light rays so taht they focus at the correct point.
Treatment
Myopia (Short-sightedness)
With Myopia the eye is longer than normal, so that light rays focus in front of the retina and distant objects appear blurred.
Treatment
Hypermetropia (Long-sightedness)
With Hypermetropia the eye is shorter than normal, so that light rays focus behind the retina. The image on the retina is blurred.
Treatment
Astigmatism
Astigmatism is a condition where the cornea is shaped like a rugby ball (oval) rather than a soccer ball (round). This causes light rays to focus at different points in the eye causing difficulty with near and distance vision. This distorted vision can cause headache and eye strain.
Treatment
Presbyopia
In young people the lens in the eye is soft and elastic and can easily focus on near and distant objects. After the age of 40, the lens becomes more rigid and cannot change shape as easily as it once did. It is more difficult to read at close range. This condition is called presbyopia and it can occur in people who already have myopia, hypermetropia or astigmatism.
