Happy 40th Birthday!
Many people find that they don’t need glasses for much of their early life. Then around age 40, suddenly their near vision begins to progressively worsen. At first they may have to strain to read the paper. Perhaps, they have to hold their phone or watch further away. Many years later, everything within arms reach may be very blurry. What gives?
These visual changes are due to something called presbyopia. It effects the structure and function of some of the internal elements of the eye. It’s a normal part of aging that occurs around 40 years of age. During the Iron Age the average lifespan was about 35 years, and nobody had to worry about presbyopia. Now that average lifespan is close to 80, presbyopic changes impact us for approximately half our lives.
Inside our eye is a lens that allows light to focus on our retinas. Overall it’s responsible for about 25% of the focusing power in the eye. It also allows for small dynamic changes that occur as one looks far away, up close, and at all distances in between. This is very similar to the autofocusing system in a camera. Surrounding the lens is a circular muscle that causes the lens to stretch out or bunch up – creating this focusing ability. Presbyopia is the sum of two natural phenomena with this system. As one ages cellular deposits begin to reduce the natural flexibility of the lens. I often liken this to flexing one’s bicep with a shirt sleeve over it – very easy to do. However, if one wears 20 shirts it becomes much more difficult. If one wears 40 shirts it becomes practically impossible. The second change that occurs is a progressive loss of elasticity in the focusing muscle. So with these changes added together the lens is naturally less flexible and the eye’s ability to drive this flexion is reduced.
What this means for one’s vision is that a little extra help is needed for near visual work. This can come in the form of over-the-counter readers, prescription bifocals, or special bifocal contact lenses. It’s important to clarify that using these devices will not make one’s eyes weaker or more reliant upon them. As mentioned above, presbyopic changes typically begin around age 40, but they continue to increase in magnitude until about age 65. This corresponds to an increase in the strength of the near prescription. One’s eyes will follow the presbyopic progression that they are destined to follow regardless if reading glasses are used or not.
Even if you are lucky enough to not need glasses and haven’t experienced these presbyopic changes there is still great value in getting an annual eye exam. Beyond checking for a glasses prescription, an annual examination includes checking the health of the internal and external eye structures, ensuring that the eyes function well together and independently, and confirming that the neural pathways between the eye and brain are working properly. With a regular exam, presbyopia and any other prescription or health complications can addressed so that one’s eyes and vision may live up to their maximum potential.