Perhaps, you have taken an eye exam for your driver's license and found that you couldn't read the signs very well. Maybe you have discovered that, as you are getting older, you have to hold books and newspapers farther away to read them. So you go to the ophthalmologist or optometrist and find that you need glasses because you have a refractive vision problem.
Light enters the eye and an image is focused on the retina.
Before we talk about refractive vision problems, let's look at how your eye works. In its simplest sense, your eye is like a camera. In the retina, sensory cells called rods and cones change the photons of light into electrical signals, which are then transmitted to and interpreted by the brain. The ability to focus the light on the retina depends on the shapes of the cornea and the lens, which are controlled by their inherent shapes, their stretchiness or elasticity, the shape of the eyeball and sets of attached muscles. See Figure 2 .