How You See the World | How the World Sees You

Treating Presbyopia (Eye condition which necessitates bifocals) with Contact Lenses: 

For years contact lens wearers considered the onset of presbyopia to be the time to make the forced switch fromcontacts to eyeglasses. Many are finding that this need not be the case. While contact lens manufacturers scramble to be the first to perfect and market a functional bifocal contact lens, the public has not embraced them in huge numbers. Meanwhile, more and more contact lens wearers are finding that they can treat their presbyopia with Monovision contacts.

Monovision doesn’t denote any special type of contact lens, but rather a special type of contact lens fitting. With monovision, the doctor fits you with a contact lens to correct one eye for distance vision while fitting your other eye with a contact lens for near vision. While this arrangement may sound unorthodox, monovision has been proven to be effective. Erie, Pennsylvania Optometrist James Piersol estimates, “Over eighty percent of my presbyopic patients who try monovision are ultimately successful with it. It normally takes one or two fittings to get the power balanced  properly, but once you do, the patient rarely can tell that each eye is performing a separate function.” Monovision is actually not as far-fetched as it sounds. Dr. Piersol explains, “The brain is always receiving two separate images from your eyes. It normally takes the two similar images and fuses them into one three-dimensional image. With monovision, the brain receives two very different images, one clear only at distance the other clear only at near. Since it can not fuse them into one picture the brain simply chooses between the two images based on the immediate task at hand, much like a director choosing between two camera angles”.

Skeptical? Try this experiment. Take a paper towel tube and with both eyes open look at your television screen. Now alternately close your right eye and then your left. The image from your dominant eye (the right for most people) will hardly move at all while the image from your non-dominant eye will jump noticeably. This is because as you sit there watching TV your brain is “choosing” the image from the dominant eye. If you were being fit for monovision the dominant eye would be fit for distance and the non-dominant eye would be fit for reading.

While monovision contacts do offer a proven and cost effective treatment for presbyopia, they also have a down side. Since your brain would be receiving only one image for distance and only one image for near, there is a resulting reduction in depth perception. This can be a critical problem for some people’s occupational requirements.

Treating Presbyopia with Surgery:

One reason for the growth in monovision contact lens fits is the rising interest in corrective eye surgery. While the public continues to warm to the idea of LASIK and other surgical procedures to correct distance vision, a medical correction is now emerging for near vision. It is called conductive keratoplasty, or CK. CK is a non-invasive procedure where radio waves are used to reshape the cornea in order to improve focus at near. The procedure is quick, relatively painless and a bit pricey. Because CK is done on only one eye the final result is very much like monovision without the contact lenses. That being the case, most people prefer to test their tolerance for monovision with contact lenses before moving on to the permanence and expense of CK.  Since presbyopia advances with age anyone considering CK needs to understand that additional procedures may be required every 3 to 5 years to keep up with their increasing presbyopia.

In the first 200 years after Ben Franklin invented the bifocal there were virtually no changes. Your father’s bifocals were very much like your great-great grandfather’s bifocals. By contrast, in the past 5 years over 176 differentProgressive Addition Lenses (PALs) have hit the market.  Each one is somehow superior to those that came before. The technology is improving exponentially.  Before too many years pass we’ll see doctors inject soft polymer plastic into the eye’s lens sac and thereby restore the lens’s flexibility. At that point it will be bye-bye bifocals.

To learn more about proper eye care, eye wear and Shawnee Optical, please visit our website at  www.shawneeoptical.com.  

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