Are Bifocals Inevitable?
I recently turned 41, but it's not one of those landmark years where we cross over into a new decade or reach a right of passage such as the legal drinking age or medicare eligibilty.
I see people every day, however, complaining of their age-related issues and since 41, I have began mourning the waning days of my pristine vision. I walk by the racks of reading glasses at the drug store and know that I will be there soon. In my experience with patients, the inevitable "bifocal corridor" seems to be 42 to 45.
This blog will explain why we experience such predictable vision changes and what we can do to adapt.
The eye change of which I speak is known as presbyopia. This translates from Greek as "old eyes." It is basically a story of our lenses and the muscles which control them. When we buy tires, there is an understanding that they last a certain number of miles with some minor variability. Our lenses are much the same. In the early to mid 40's the lense becomes stiff. The muscles which contract to allow us to see things close become fatigued from the extra work.
Early in the course, the first noted symptoms is usually difficulty in reading small objects such as print. In poor light this is more obvious. Moving the object away from our face helps with focus. Some people finally seek help when that focal point gets beyond their reach. Another symptom is a delay in the ability to focus in going from far vision to close vision, like looking up from a book and then back to the book. Often, the low threshold for eye strain causes headaches.
Everybody experiences this stiffening of the lens with age, much like gray hair and wrinkles. Those who are nearsighted, however, fare better with presbyopia. While they still have difficulty seeing far away, the near changes are not so dramatic.
For most, a lens helps to clarify that small print. With otherwise normal vision, reading glasses will do. When baseline vision is problematic, the lens is fashioned for reading at its base-- bifocals. A different technique called monovision creates the transition side to side rather than up-down as with bifocals. Monovision tricks the brain by putting a corrective lens in front one eye and a reading lens in front of the other with hopes that the vision will blend comfortably. Some tolerate this very well and then again some do not. Contact lenses can also correct vision as bifocals and monovision.
It stands to reason that strengthening those ciliary muscles that move the lens could overcome its stiffness. Unfortunately, however, ciliary muscle exercises do not effectively improve vision in the state of presbyopia.
The latest in corrective vision is surgery which sculpts the cornea, the clear skin that covers the lens (LASIK). While LASIK is available for presbyopia, low light situations still cause blurred vision. Other surgical options that may offer promise in the future include implantable replacement lenses and bands that ease the burden of the ciliary muscles.
Hope for those with presbyopia gets even more progressive and high tech with a technique called perceptual learning. Despite what goes on in the eyes, the image gets processed in the brain. Perceptual learning works at the level of the brain. This technique sort of provides a tuner to dial in a sharper image via a battery of exercises. Experimental reports show promise but things are a ways off.
So, as it stands, the best option may be those reading glasses. Like it or not, for me it will be inevitable. I will don them with pride as a mid-fortysomething.