How Are Bifocal Contact Lenses Made
Bifocal contact lenses were made because we found out that as we neared the age of around 40, our eyes lost the ability to readily change focus from distant objects to near ones. This inability to adjust eye focus is called presbyopia.
For most folks the biggest problem shows up in the form of not being able to easily read like we used to. Most of us find reading particularly difficult when there are low light levels, when we get tired or when the print is just too small.
It's easy to see how a regular set of glasses can be manufactured with bifocal lenses. The top part of the lens is designed for distance vision while the bottom part of the lens has the near-vision prescription in them. Since glasses can be put on only one way (at least for most people!), the lens position stays constant. But what happens with contact lenses?
Some folks use two different monovision prescriptions - one eye gets the distance-vision correction and the other gets the near-vision correction. This works very well for some people but it's not recommended for use while driving a vehicle.
An alternative to this is to use bifocal contact lenses. There are three designs used that are called translating, aspheric and concentric.
- Translating lens design, also known as alternating, works much like a standard pair of glasses. These lenses are manufactured with a flat edge on the bottom that is designed to keep the lens from rotating in your eye when you blink. This assures that your near-vision prescription stays on the bottom and does not rotate around to where your distance-vision needs to be.
- Aspheric lens design, also known as simultaneous, puts both prescriptions near the pupil area. Your eyes learn to adjust to the lens and naturally choose where to focus.
- Concentric lens design puts the distance-vision prescription in the middle of the eye and the near-vision correction on the periphery of the lens. Again, your eye naturally adjusts to the correction that the lens provides.
Take the time to try out each of these bifocal lens designs. You'll want to make sure you choose the one that's most comfortable to wear.
