Getting through your eyeglass prescription can be a daunting task, especially if you are unaware of prescription glass details. Going for the eye exam equipped with knowledge of multifocal prescriptions
can help you make a smarter decision when the time comes to pick out the glasses like Bifocals.
What are Bifocals?
Bifocals or “lined bifocals” contain two prescriptions within the same lens and can correct both nearsightedness and farsightedness. It consists of prescription for reading in the bottom of the lens and
the distance prescription in the top of the lens. When you’re looking at someone who is wearing bifocals, you can see the line between their nearsighted and farsighted prescription. This is because in a
bifocal lens, the two different areas of vision correction are divided by a distinct line that sits horizontally across the lens.
Two lenses, Two functions
The bifocal lenses incorporate powers of two lenses where progressive multifocal lenses gradually change in power from the top half of the lens to the bottom, which creates multiple lens powers. This allows the individual to focus on objects both at a close range and at a distance as well without the need to adjust or remove the glasses. Generally, you look ahead or up through the upper section of the lens to look at objects at distance, and you look down and through the near segment of the lens to look at the reading material or close-up work. Usually, bifocals contain focal lengths that correct close vision of 12 to 18 inches from the face and distances of 10 feet and beyond.
Alternative to Multifocals
Bifocals are the most common type of multifocal. If you have more than one vision problem, you’ll probably get glasses with multifocal lenses, like bifocals or trifocals. These have two or more prescriptions to correct your vision. They are convenient alternatives for people over 40 years old who require separate glasses for distance and near vision. There are certain requirements on the frame for bifocal glasses. That’s due to presbyopia, an age-related change that affects your eye's lens. Bifocals and
trifocals are conventional options for glasses because when looking through them wearers may notice that images may seem to “jump” as your eyes move past the defined boundary between the distance
and near part of the lens.