The best way to understand function of the eye is to compare it to a camera. A camera creates images by focusing on an object and allowing specific amounts of light to pass through a hole to create a visual impression on film. The eye functions in much the same way.
When light enters the eye, it passes through the cornea (camera lens) where 2/3 of focus is achieved. The light then passes through the pupil where the iris (aperture) adjusts the amount of light that is allowed to enter. The remaining 1/3 of focus is then achieved when the light passes through the lens (camera lens).
The shape of the lens can adjust (either thinner or thicker) by tensing or relaxing the muscles of the eye. The focused light finally reaches the retina (film) where it is converted by the rods and cones into a signal that can travel to the brain (film development). Once the image reaches the brain, you have sight.
What causes vision problems?
Changes in the shape and size of your eyes can cause problems that affect the way you see things that are close up or far away. These problems are referred to as refractive disorders. Refractive disorders include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. Presbyopia is an age-related eye condition that affects everyone some time after age 40, making it difficult to focus on objects up close. This section of MyClearVision.com will help you to understand these disorders and conditions and what they might mean to you.
