Like any other organ and its gradual progression over the years, our eyes are also bound to experience various issues that can cause many problems in vision and perception. For example, one needs separate focusing powers for distance and near with age. Those who don’t need powered spectacles for distance may require them for reading alone. It can create quite the task of handling different powered spectacles for different viewing distances. However, quite a few aids and lenses can help us see clearly, bifocals being one of them. Keep reading to understand bifocal lenses thoroughly before going in for the lenses.
What is a Bifocal Lens?
Bifocal lenses are the type of lenses that help correct vision for people with short-sightedness or long-sightedness along with near-vision or reading numbers. Wearing eyewear fitted with bifocal lenses helps you see at a far (clinically measured at 20 feet or 6 meters) as well as near vision (usually measured at 40 cm or one’s customary reading distance) with just one pair of spectacles. In simpler terms, you can consider bifocal glasses as a pair of ordinary eyewear that comes with lenses that help you read and see far through a single lens. The near vision power is placed towards the lower half of the lens, and the far vision part is placed in the top part. The line distinction between the two powers on the surface of the lens is quite visible.
Although it might be a little uncomfortable at first, you will gradually adjust to the line separating the bifocal lens from the regular section of the eyeglasses. These lines are removable with the help of a newer version of the bifocal lens, known as a blended bifocal or a more advanced technology of spectacles called progressive lens. Go on below to learn more about what are bifocal lenses and their usefulness.
Types of Bifocal Eyeglass Lenses
From Benjamin Franklin’s self-made bifocals to the current times where one can choose from more than one type of bifocal lenses, there is a variety from which you can select bifocal lenses or bifocal eyeglasses per your needs and requirements. Here are the most common types of bifocal lenses found at R. Kumar Opticians:
Traditional Bifocal lenses
This type of bifocal lens usually comes with a clear separation which demarcates the upper part from the lower part of the bifocal eyeglasses. Thus, the top of the lens helps correct far vision (usually measured at 6 meters or 20 feet), while the lower part reduces near vision (usually measured at one’s habitual working distance at near). Traditional bifocal spectacles are made in the following arrangement:
Half-moon also known as a flat top.
Spectacles with a flat top or half-moon bifocal lenses feature a small portion that resembles the letter ‘D’ lying on its side. This flat-top section is positioned nasally and points down towards the bottom of your bifocal glasses. According to the choice, you can choose from a 25mm segment to a 28 mm segment, and the upper portion has a visible line in the lens.
The round bifocal lens ensures that you can reach the reading area of the segment with minimal effort. These round bifocal lenses measure from 22 to 24 mm in size but are not commonly worn anymore.
Narrow rectangle or ribbon segment
These bifocal lenses come with a narrow rectangular portion that helps you during activities that need you to look closely, like scrolling through phones, reading books, and other related activities.
A full bottom also known as the executive segment.
An executive bifocal pair of eyeglasses has the top half separated from the lower half. The distinction is visible and goes all the way across the lenses. These types of bifocal eyewear were once popular with office and desk workers. However, this type of bifocal eyeglasses dropped out of favor since the line goes from one side to the other side of the lens.
No-line Bifocals or Blended Bifocals
These are essentially round segment bifocals in which the demarcating line is so finely blended that it is virtually invisible as a line. It is a cosmetically better-looking bifocal but essentially a bi-focal and should not be confused with a progressive lens.
How Do Bifocal Lenses Work?
Bifocal eyeglasses come with two lenses placed in the same frame. These are helpful for people with eye issues like Presopiaby. The upper part of the bifocal eyeglasses helps you see objects and things at a distance, while the lower half of the bifocal glasses help you in reading and seeing objects at a closer distance.
The lenses sit one upon the other, which allows you to adjust from one prescription to the other effortlessly. As mentioned in the previous paragraph, bifocal spectacles are almost always prescribed to people above 40. These with,, bifocal with, eyeglasses are prescribed due to the natural degradation of vision.
What is a Trifocal Lens?
With the same principles on which bifocal lenses have been created, trifocals are made with three different focal points within one lens. The three zones of vision in a trifocal lens are as follows:
Thus, similar to bifocals, trifocal lenses address three vision issues at once. Another great feature of trifocal lenses is that they can be customized for different career fields or hobbies. Trifocal lenses are mainly of two types that are available for eyeglasses:
- The flat-top trifocals lens in which the intermediate vision area is placed in a D-shape allows for improved peripheral vision and is easily adjustable for people.
- In the executive trifocal lenses, the intermediate area is thinner when compared to the flat-top lens and takes a little more time for adjustment.
Trifocal lenses are beneficial for their users. However, there are a few advantages and disadvantages, which are as follows:
- Three different zones of vision are provided with trifocal lenses. But there are visible lines on the lenses.
- Trifocal lenses provide better focus at an arm’s distance but have very few customization options.
- You can adjust quickly when moving on from standard bifocals and other eyewear with trifocals. But then, it would be necessary for you to change prescriptions as you grow older possibly.
However, with modern-day progressive lenses covering this scope of application and offering clear vision at more than just three specific distances, trifocals are hardly dispensed these days. Also, progressive lenses are aesthetically better looking where it looks like a single seamless lens. Since the power transition in a progressive lens is continuous, it is easier for the wearer to adapt to.
At R. Kumar Opticians, you can get not only single vision lenses but also get ECPs advice on whether you need bifocals or progressive lenses to help your eyes see better.
What is a Multifocal Lens?
Multi-focal refers to a spectacle lens that has more than one focal power incorporated in a single lens. In the most basic form, a bifocal i.e. a lens with two focal powers, typically for distance and near visions is multifocal. But the word bifocal is more popular for this kind of lens.
Next, a lens with three focal powers, typically for distance, intermediate (desktop computer), and near visions is also a form of multifocal. However, the word trifocal is a more commonly used term for such a lens.
The word multi-focal, in common usage, refers to a lens with more than one, two, or three focal powers incorporated into a single lens. Special technology makes a modern-day version of a multifocal lens. There is a smooth continuous transition of powers from distance to intermediate and near in this technology.
So, instead of what one would image as a step-wise change of power from one power to another and multiple lines and segments separating each focal power, the change from one power to another is a continuous smooth transition. Such a lens with the progressive change of power from far to near visions is called a progressive addition lens, PAL for short, and more commonly called a Progressive lens.
Hence, the word multifocal is a broad word that would technically include every kind of lens that incorporates more than one focal power or length in a single lens. So, for example, IT can be a bifocal, trifocal, or progressive lens.
What is a Progressive Lens?
Progressive lenses are the most updated spectacles to correct presbyopia or age-related vision issues. They are the modern-day replacement for the bifocal or trifocal lens. They are also known as invisible, seamless, or no-line bifocal lenses; however, invisible bifocals are technically bifocals with the blended line. In contrast, progressive lenses are much more advanced versions providing multiple seamless focuses throughout the lens.
In addition, there is a progressive, seamless, continuous transition of power from far to near visions covering all distances in between in a progressive lens. So the power would progress seamlessly from far vision correction to near vision correction to accommodate all distances in between.R. Kumar Opticians have the best collection in the progressive lenses category, which helps you get a proper solution for your eyes.
Difference between Single-vision vs. Bifocal Lens
As mentioned at the very beginning of the blog, the eyes are an organ that shows aging changes with time. IT is most commonly observed that around or after the age of forty, you might begin to have issues with focusing your vision, especially for near vision. For people who do not need a separate prescription for distance, a pair of single-vision reading glasses or near vision glasses will suffice. However, if you have a separate prescription for distance or have the frequent need to switch between far and near visions, you would need bifocal lenses with far and near powers incorporated in one lens. There is a difference between single vision and bifocal lenses mentioned below:
- Lens Type
A single vision lens is also known as a monofocal lens since it aids in the correction of your vision for a particular focal length. Also, the lens has a uniform power all over. which means that your eyewear has the same power. On the other hand, bifocal lenses come with two different focal lengths, which helps in improving your vision for both nearsightedness and farsightedness.
- Vision Correction
Single vision eyewear gives you vision correction for only one type of focal length suitable for your vision. The single-lens eyewear can aid in seeing objects at one specific distance but not both lengths at once. Bifocal lenses are two-part lenses that serve for both distances: far and near. The upper part of the bifocal aids in far vision, and the lower part of the lens provides for near vision.
- Easy usability
With single-lens eyewear, you will need to interchange with a pair of eyewear that can assist with looking at distant objects. But, with the help of bifocal lenses, you can look at both close and far things without changing eyewear every time.
Therefore it is understandable that bifocal lenses are a better choice than single-lens eyewear. The best quality bifocal lenses are available from R. Kumar Opticians.
Difference between Bifocals vs. Progressive Lens
Bifocal vs. progressive lenses is not a debatable topic as both types of lenses serve the same purpose of correcting age-related vision disorders for people above 40. Although both lens types serve a similar purpose, each type of lens has some exceptionally well-defined differences that help in different ways for the wearer. Read further to understand how bifocals and progressive lenses help you in different ways:
The most visible difference is that a progressive lens does not have any demarcating lines or specific segments of different focal powers seen on the outside. Hence, visually the spectacles look like normal spectacles rather than ones made for someone with age-related reading powers.
A bifocal has two focal segments, a trifocal has three, so these provide clear vision for two or three specific working distances. In a progressive, all distances from far, near and in-between are covered. Hence, the wearer has more good spectacles that can be used for a more active lifestyle that is not restricted by two or three specific distances. IT is ideal for modern urban living. It gives the flexibility to use for diverse activities and can be used all day without causing fatigue to the eyes.
There is a sudden change in power in each focal segment in a bifocal or trifocal. As the eye moves from one focal length to another, there is a jump in the image. It often takes time for a wearer to get used to. In a progressive lens, the progression of power is seamless, smooth, and continuous. Hence there is no sudden change in power or image jump. As a result, the adaptation is faster and smoother.
Bifocal lenses clearly distinguish between the near and far vision on prescription lenses.
On the other hand, progressive lenses give you seamless vision across varying distances with no boundaries.
To summarize, after reading the above, it will be easier for you to understand what is a bifocal lens. However, the difference between bifocal and progressive lenses and how a single lens varies from bifocal lenses are made visible. All the different types of lenses are available at R. Kumar Opticians.
Bifocal lens used for which defect?
Bifocal spectacles are used to correct vision for two distances, mostly far and near distances, occasionally for intermediate (desktop) and near (reading) distances.
Who invented the bifocal lens?
Benjamin Franklin is most commonly credited as the inventor of -bifocal lenses in 1784. He was tired of interchanging between two different eyeglasses for farsightedness and nearsightedness by placing one-half of each type of lens in a horizontal position.
Can I drive with bifocal spectacles?
Of course, you can drive with bifocal lenses. Decades before the progressive lenses were introduced and several years later, bifocals were the lenses of choice for spectacle users who required far and near vision correction in a single pair of spectacles. These were convenient for day-to-day activities. However, with the development of progressive lenses, today, progressive lenses are far more accessible and widely available. There are obvious benefits that outweigh those of bifocals. But for regular far and near vision activities like driving and reading.
How much do bifocal, trifocal and multifocal lens cost?