PRESBYOPIA

The basic process of sight begins when light rays enter the eye through the cornea, the front surface of the eye. The cornea begins bending the light rays toward the back of the eye. The light then passes through the lens of the eye, which directs the rays toward an exact spot on the retina in the back of the eye. When that light reaches that perfect spot on the retina in a normal eye, the image seen is clear and in focus.

The lens of the eye, (the white body to the left of the arrow in the diagram), is very important in the process of sight. In a young person, the lens is flexible and can bend easily to help focus on near and distant objects. Presbyopia is a condition in which the lens loses its flexibilty, making it difficult to focus on near objects. This effect is similar to hyperopia, but the cause is different. Presbyopia usually affects people in their late thirties and early forties, often creating the need for reading glasses or bifocals.