The iris controls the amount of light entering the eye through the pupil. The light rays are focused by the cornea and the eye’s clear lens onto the retina. The retina then transforms the light into electrical impulses that travel through the optic nerve to the brain, where they become the images you see.

Normal vision

Light rays pass through the cornea and focus on the retina. Both distant and close objects appear clear.

Myopia occurs when the eyeball is too long. Light rays focus in front of the retina and distant objects appear blurred.

With astigmatism, the curve of the cornea is irregular. Light rays focus at multiple points and both distant and close objects appear distorted.

The lens hardens with age and is no longer able to focus on close objects.