1. Optics of the Eye

2. Structure of the eye
In a normal eye the cornea and the lens will adjust the focal length of the eye so that the image is formed on the fovea, which is the spot on the retina that allows a person to see most clearly. Interestingly, the eye contains a converging lens that forms a real image– this means the image is actually upside down in the eye. The human brain compensates for this, though, and humans see the object as being upright.

3. Nearsighted
If a person is nearsighted the eyes focus in front of the fovea causing objects that are at a distance to be blurry.

4. Nearsighted correction
By using a diverging lens the image is moved back to the fovea and the person can see clearly.

5. Farsighted
If a person is farsighted the eye focuses at a point behind the fovea.

6. Farsighted correction
By placing a diverging lens in front of the eye the image is brought forward to the fovea and the person can see clearly.