A hardening of the lens of the eye which causes poor reading vision
Through the natural aging process, changes occur in the lens of the eye that interfere with our ability to see clearly. The first change begins about the age of 40, when the lens loses its elasticity and begins to harden. When this occurs, the lens can no longer change shape to focus properly. As a result, close objects cannot be seen clearly and reading begins to be a problem. This hardening of the lens is called presbyopia.
How does the lens work?
In normal vision, light enters the eye and is focused by the lens on the retina. The retina transforms the images into electrical impulses, which are transmitted to the brain by the optic nerve. If the lens does not focus properly, vision will be distorted.
The lens continually changes shape to focus on objects that are various distances from the eye. The shape of the lens is controlled by the zonules, thin muscle fibers that hold the lens in place. The zonules contract and relax to control the size and shape of the lens. When we look at something close up, the zonules relax, allowing the lens to become fatter. When we gaze into the distance, the zonules contract and cause the lens to become thinner.
How Does Presbyopia Affect Vision?
At birth the lens is soft and flexible, and its shape is easily controlled by the zonules. As we age, however, the lens gradually hardens and becomes resistant to changes in shape. Since the older lens cannot change shape as easily as it once did, the eye has increasing difficulty focusing. This loss in focusing ability, or presbyopia, results in blurred or distorted vision when looking at close objects.
What Causes Presbyopia?
Presbyopia is a natural result of the aging process. Everyone will eventually experience some degree of presbyopia, beginning about the age of 40. In fact, presbyopia is one of the most predictable, routine age changes that occurs in the human body.
What Are the Symptoms of Presbyopia?
The most common symptoms of presbyopia are blurred vision of near objects and difficulty doing close work. Many people find reading difficult and hold the material farther away in an attempt to see more clearly. A slowness in changing focus from near vision to distance vision may be noticed. Eye fatigue and headache after close work are also symptoms of presbyopia. In addition, farsighted people will usually notice the symptoms of presbyopia sooner than those who are nearsighted, as nearsighted persons can simply remove their glasses to see close objects more clearly.
How Is Presbyopia Treated?
Unfortunately, no treatment will slow the progression of presbyopia. However, corrective lenses can be used to bring things back into focus. In many cases, new glasses are required about every two years to overcome blurred vision caused by an increased hardening of the lens.
Many options for corrective lenses are available. Reading glasses can be worn when doing close work. However, distant objects become blurry when viewed through reading glasses. Therefore, some people choose bifocals, which offer good distance vision through the top and clear reading vision through the bottom. People who have good distance vision without glasses may use half glasses to correct presbyopia. Half glasses are worn for close work and allow for viewing over the top of the frames when distance vision is required. Two pairs of glasses or different contact lenses (one for near vision and one for distance vision) may also be used to correct presbyopia.
If you are experiencing difficulty with reading and close work or have other vision problems, you should obtain a complete eye examination.