What Are Bifocals?

If you’re over age 40, you may have noticed you’re having trouble reading magazines, restaurant menus, text messages and other things up close. This may be a symptom of presbyopia. Presbyopia is a natural loss of near-focusing ability that makes it hard to see clearly up close as you age.

You might be thinking it’s time to try some type of vision correction. Bifocals could be the solution.

What Are Bifocal Glasses?

When you’re young, the natural lens inside your eyes is flexible. It can easily shift focus so you can see clearly up close and far away. As you get older, this lens becomes thicker and starts to harden. This makes it less flexible, which affects your near vision.

Bifocals are glasses that correct this issue by including two lens powers (or strengths) in each lens. The bottom part (or segment) of the lens has your near-vision prescription so you can see better up close.

If you can’t see objects clearly when they’re far away, the top segment of the bifocal lens will have your distance prescription. If you can see clearly far away, the top segment is clear, because no distance vision correction is needed.

The History of Bifocals

Benjamin Franklin, one of the Founding Fathers of the United States and a glasses wearer himself, invented the first multifocal lens for eyeglasses in the late 18th century.

Around 1784, Franklin created “double spectacles,” what later became known as the Franklin bifocal. After getting tired of switching between two pairs of glasses — one to correct distance vision and one to help with reading — he realized there was a way to create a single pair with both prescriptions.

Franklin cut the lenses from both pairs in half lengthwise, using the top half for distance and the bottom half for reading. He then glued the halves together to create his new bifocal lenses, which had a line all the way across to separate the lens powers. Franklin’s basic design was used for 100 years and still exists in a modified form today.

In the early 1900s, thinner and more attractive lenses were used to refine the Franklin bifocal design. These adjustments continued as smaller, rounded bifocal segments for near vision were developed.

More recently, techniques were developed to create a “blended” or “invisible” bifocal, which blends the segment for near-vision correction into the segment with distance correction so there is no line dividing the two.

How Do Bifocals Work?

Bifocals all work the same way to help you see both distant and close-up objects clearly. You look straight ahead through the distance portion of the lens to see objects far away. You look down through the near-vision segment of the lens to read or see objects up to 18 inches away.

Bifocal Lens Options

The near-vision part of bifocal lenses comes in a few different shapes:

• D-shaped – This is the most popular bifocal lens. The near segment is rotated 90 degrees so the flat part of the "D" is facing up. D-segment bifocals are also called "flat-top" or "straight-top" bifocals.
• Round segment – This segment type was originally designed to make it easier for wearers to see through the near-vision part of the lens. However, the round shape makes the near-vision segment more narrow at the top, which can be uncomfortable for some wearers.
• Blended – This shape is also called the "invisible" bifocal lens. It’s a round-shaped near-vision segment that blends into the distance part of the lens, making the round segment virtually invisible. This is a good option for wearers who want a no-line bifocal.
• Ribbon segment – A ribbon-segment bifocal lens has a narrow rectangular band with the near-vision prescription across the middle of the lens. The distance-vision sections are above and below this ribbon.
• Executive/Franklin/E-style – This is the original bifocal lens type with the distance-vision segment on the top half and the near-vision segment on the bottom half.

Occupational Bifocals

Occupational bifocal lenses provide the same vision correction as traditional bifocals but are designed for a particular job or hobby rather than general-purpose wear. These lenses include:

Double-D bifocal

While the double-D lens is divided into three sections, it’s still considered a bifocal because it only has two lens powers. There are two near-vision segments — one at the top and one at the bottom — and the rest of the lens corrects for distance vision.

This lens is a good option for car mechanics who need to see their tools and other objects nearby and need to work on vehicles on a lift above them. The upper segment of the double-D enables them to see the undercarriage of the car by slightly looking up instead of tilting their head far backward. They also don’t have to wear their glasses upside-down as they would need to do if they had regular bifocal glasses.

Golfer's bifocal

If you play golf and wear bifocals, you may have found that the near-vision segment of your lenses gets in the way when you prepare to hit the ball or try to line up a putt. To fix this, a small (often round) near-vision segment is placed in the lower outside corner of just one lens.

This segment is in the right lens for right-handed people and in the left lens for left-handed people. This way, the near segment is completely out of your way when you're on the course but gives you enough near-vision power to read your scorecard and see other things clearly up close.

Bifocals Pros and Cons

Like any type of eyewear, there are advantages and disadvantages to wearing bifocals.

Pros

One of the best reasons to try bifocal lenses is convenience. With bifocal glasses, you only need one pair of glasses to see clearly close up and far away. Here are a few more reasons they may be right for you:

• Cost – Bifocals usually cost less than other multifocal vision correction options, such as progressive lenses. A more advanced version of bifocal and trifocal lenses, progressives also correct presbyopia.
• Easier adjustment - Since bifocal glasses have two distinct segments of vision correction, it’s often easier and faster to adjust to them than it would be progressive lenses.

Cons

There are some potential drawbacks to bifocals to consider. For example, you may be distracted by the line in between the top and bottom halves of your bifocal lenses. Or you may feel like the line cuts your line of sight in half.

Other cons of bifocal glasses include:

• Instant aging effects – Some people worry that the obvious dividing line between lens segments will make them look older when wearing bifocals.
• Potential visual distortions – Lenses with two vision zones can cause some visual distortions. One common issue among wearers is having trouble going up stairs or stepping up on a curb. When you look down at the ground, your feet may look bigger and you may feel higher above the ground than you actually are. This is usually temporary and goes away the longer you wear your bifocal glasses.
• Adjustment period – Even though it’s easier to adjust to bifocals than other multifocal options, you still need to adjust, especially if you’re used to single-vision lenses. Until you’ve trained your eyes to look through the right section of the lenses at the right time, you could experience headaches or nausea.
• Not a complete vision solution – Bifocals can help you see distant objects clearly when you’re driving and see clearly up close when you’re reading or doing other near tasks. But bifocals don’t have an intermediate zone, so you may still have trouble viewing your computer monitor or other things at a median distance.

When to See a Doctor

If you’re having trouble seeing things clearly at any distance, it may be time for vision correction. Contact your eye doctor and schedule an appointment for a comprehensive eye exam. After assessing your eye health and vision, your eye doctor can help you determine the best option for your vision needs.