Bifocal Contact Lenses : Understanding New Lens Options
In years past, optometric patients who needed correction of their distance vision as well as correction of their near vision (a condition known as "presbyopia") only had the option of wearing bifocal glasses. In more recent years, new bifocal contact lenses have been developed which have given a new freedom to presbyopia patients, allowing them to enjoy the convenience and appearance of contact lenses which were not available to them previously. Not only have the alternatives for such patients been expanded by the development of bifocal contacts, but new options and varieties have been made available to provide contact lens wearers with choices in different types of bifocal lenses that correct vision in different ways, including new alternatives for patients with conditions like astigmatism. To add to the various new alternatives available to choose from, brands like Acuview and Bausch and Lomb also have added their own unique types of lens options and characteristics a patient can choose from. With all of these new options and choices, the selection of the best bifocal contact lenses can seem like a challenging task for most patients. However, with a little understanding the general categories and features that include most of these new lenses, a patient can simplify the task of picking the best lenses for themselves.
Simultaneous Vision Correction - This type of contact lens is bifocal, but unlike regular bifocal glasses which have the distance vision correction in the upper part of the lens and the near vision correction in the lower part, a simultaneous bifocal contact has both types of correction occurring simultaneously within the area in front of your pupils. Amazingly, your brain automatically determines which correction to use as needed.
Concentric Vision Correction - With bifocal contact lenses that are concentric, the distance vision correction is usually located close to the center of the lens, while the near vision correction is located around the outer edge. This makes sense because, when you look down at something close, like a book, your eyes will be looking through the outer part of the lens. In the past, some lenses were produced with concentric circles of diffractive gratings (under the trade name of "Diffrax") which allowed both near and distance correction to be placed on rigid gas permeable lenses; however, these were discontinued due to high manufacturing costs. The drawback of concentric lenses can be that you may need to look at near objects which are straight ahead, or you may need to look at distant objects while looking down or up, and these lenses may not accommodate these situations very well.
Alternating Vision Correction - This type of correction is closest in operation to regular bifocal eyeglasses, with the distance correction in the upper part of the lens, and the near vision correction in the lower part. One problem with this design is that the contact lens can float and rotate on the eye so the near correction area moves to the top. To prevent this, the lower part of the lens is usually weighted so it naturally floats to the bottom. Because of this, you usually have to blink and wait when you first put them on, to allow the lens to rotate to the proper position.
Monovision - These are not really a type of bifocal contact lenses at all, but is more of a method of wearing regular non-bifocal lenses to achieve the same effect as wearing bifocals. Essentially, monovision involves wearing a distance- correcting lens on one eye, and a near-correcting lens on the other. Not everyone can do this. At first, the patient feels like they are cross-eyed. However, the brain can soon adjust to the different lenses on each eye, and you can't tell the difference. This wearing style can be a real advantage for people with astigmatism, because you can use regular non-bifocal lenses on each eye, which can be prescribed to correct whatever astigmatism you may have, and it eliminates the need to supplement your contacts with eyeglasses for close-up work which would sometimes otherwise be required with bifocal contacts.
Lens Convenience Features - Contact lenses can sometimes get lost in your soaking solution and can be hard to find, especially when you're sleepy first thing in the morning (and you can't see because you don't have your contacts in yet). Bifocal contact lens brands like Acuview, and Bausch and Lomb, have added slight tinting to their bifocal contact lenses to make them easier to find in the clear solution, without being tinted enough to affect your eye color. It's also easy to get your contacts turned inside-out, which can really be uncomfortable; so brands like the Acuview bifocals have markings such as "1-2-3" imprinted on the contacts, making it easy to tell if the correct side is out. Bifocal lenses are sometimes limited in the levels of correction they provide; in response to this, Bausch and Lomb offers a "multi-focal" feature to provide a much broader range of available correction.
Disposables - Many people still believe that you can't get bifocal contact lenses that are disposable, but that is no longer true. The same varieties of disposable lenses are now pretty much available in bifocals, as are available in non-bifocals, including daily disposables.
All of the bifocal contact lenses on the market today may seem to have an endless number of arrangements and features. However, just about all of them will fit into one or more of the basic categories described above. By understanding these categories, you can avoid being overwhelmed by all of the lens choices. You will have a much better grasp of the pros and cons of each type of lens you consider, and as an educated consumer, you will be able to confidently choose the type of contact lenses that are best suited to your own needs.
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