A: Throughout the average day, we focus on different distances. From the clock on the wall, to the computer, to the report on the desk in front of us and back again; the natural lens in the eye is always changing to accommodate the things we see. The natural lens sits directly behind the iris in a protective sac called the capsule. When looking into the distance, the muscles in the eye relax, allowing the natural lens to become long and thin. When looking up close, muscles in the eye contract tightly and the natural lens is allowed to round and shorten. This process is called accommodation or, more simply, focusing. It takes less accommodation for distance vision, and more to see up close.
Typically around the age of 40, or shortly thereafter, the ability of the average adult’s eyes to accommodate properly decreases. The muscles responsible for controlling the lens begin to weaken and the lens itself begins to thicken. It becomes less pliable and is unable to relax as it did in the earlier years of the patient’s life. It is often around this time that reading glasses become necessary. These simple lenses essentially refocus the image to provide clear vision without the need for natural lens accommodation. As we continue to age, our abilities to focus continue to decrease. Eventually, most people find they need to increase the power of their reading glasses. As a general rule, you begin with +1.00 reading glasses, and eventually build up to around +2.50 or +3.00. Your optometrist can help you determine exactly what strength of reading glasses is best for you.
Information provided by Dr. Matthew Ward, O.D. from Eye Care of Iowa, 5075 E. University Ave., Pleasant Hill 265-5322.