How Do Bifocal Contact Lenses Work?
Many people aren’t even aware that there are such a thing as bifocal contact lenses. It seems impossible – a contact that offers two prescription strengths at once, and stays in position on the eye. But they’re real, and bifocal contact lenses a fantastic option for people who are tired of peering down into the bottom of their eyeglasses to read, or who want to stop switching between two pairs of glasses for different purposes. The Acuvue, line of bifocals, manufactured by Johnson & Johnson, are perhaps the most popular, and are even available as toric lenses for people with astigmatism.
The need for reading glasses that most commonly results in the use for bifocals is called “presbyopia.” It’s the reason that people develop “old eyes” as they reach middle age, a difficulty in focusing on things close up like a book with fine print or a restaurant menu. It’s believed that it’s caused by a gradual loss of flexibility in the eye’s lens, which makes it more difficult to focus on things that are close.
When this occurs in people who already need correction for their distance vision, two different prescriptions are needed to correct two different problems. The traditional solutions have been to either switch between two pairs of glasses or to wear bifocals, with the prescription for close vision on the bottom of the lens to facilitate reading.
What Bifocal Lenses Are Available?
Now there are also bifocal contact lenses available in both soft and rigid materials, including disposables. Like bifocal eyeglasses, bifocal contacts have two prescriptions in one lens.
There are two different types available, and they work two different ways. “Translating” lenses (also called alternating vision lenses) are like old-style bifocal glasses – your pupil looks out through two different prescription strengths depending on whether your looking up or down. They’re smaller than regular contact lenses, and weighted so that – like bifocal glasses – they stay in place as you move your eye, so when you’re looking down at a book or a newspaper, you’re looking through the part of lens designed to correct your near vision.
The other type of bifocal contacts are “simultaneous vision” lenses, through which your eye looks at through both the distance and close-up prescriptions at the same time. This sounds impossible, but the human brain is an amazing thing – it adjusts to seeing the correct prescription depending on what you’re looking at.
These come in two styles – the “concentric ring” type of bifocal contact lens has one prescription in the center and changes strength as it moves outward from the middle. They work because your pupil expands or contracts based on the distance of what you’re focusing on. “Aspheric multifocal” contacts are even more amazing, as they layer different prescription powers on the same part of the lens, and it’s up to your brain to translate what your eye needs at any given time – they take time to get used to, but eventually your eyes become trained so that you aren’t even aware of it.
The new technologies that have made these advancements possible are impressive, and it’s now possible for people with astigmatism to get toric bifocal contacts and for those who need bifocals to wear soft contact lenses – even colored contacts. Talk to your eye doctor about your options, and you may find yourself putting aside those reading glasses for good.
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