If you have recently been to the optometrist for new glasses or are planning on a visit soon, you may have some questions. Among the most common queries people have is the difference between single vision and bifocal lenses.
Single vision lenses are used to sharpen your focus for either nearby or faraway images. However, they cannot be used to sharpen your vision for both. Bifocal lenses enhance your vision for both nearby and faraway images.
It is possible that at this point, you still have some questions. Read on to learn more about the differences between single vision and bifocal lenses. You will also find some examples of both types of lenses to help you determine which may be right for you.
Differences Between Single Vision and Bifocal Lenses
Single vision lenses are also sometimes called “monofocal” lenses. Knowing this can help give you a better understanding of the difference between the two types of lenses.
The suffix “focal” essentially means vision. The prefix “mono” means single. When put together, this is just a fancier way of saying “single vision.” It refers to the fact that these types of lenses enhance your vision in just one way.
The prefix “bi” means two. When put together with “vision,” you get “two vision,” which may sound a little strange. Really this just means these types of lenses enhance your vision in two different ways.
Determining whether you need single vision or bifocal lenses and which types of these lenses you will need depends on the vision issues you are experiencing.
Vision Issues Corrected by Single Vision Lenses
Single vision lenses can help correct a host of vision issues. Additionally, some individuals who use bifocal lenses on a daily basis may also use single vision lenses for specific tasks. These are some common vision issues single vision lenses can help with:
- Astigmatism – Perhaps the most common vision issue, most people have some degree of astigmatism, which is an altered curvature of the lens and or the cornea.
- Hyperopia – Also known as farsightedness, this refers to an issue in which individuals can see objects well at a distance but not when nearby.
- Myopia – Also known as nearsightedness, this is the opposite of hyperopia and refers to when individuals can see nearby objects well but have difficulty seeing distant objects.
- Presbyopia – As individuals age, the lens of the eye loses flexibility. This can make it difficult to see nearby images. However, the ability to see distant objects is not generally affected.
If you have been diagnosed with one of these conditions, single vision lenses may be beneficial.
Vision Issues Corrected by Bifocal Lenses
In some cases, you and your optometrist may decide bifocal lenses are a better option. For example, if you have struggled with myopia, you may only have needed single vision lenses up until this point. If you are beginning to develop presbyopia along with your myopia, bifocal lenses may now be necessary to help correct both issues.
However, there are other situations in which bifocal lenses can be beneficial. Children are often prescribed bifocal lenses if they have difficulties focusing on the whiteboard in class and develop eye strain because they spend much of their time reading and writing.
Using bifocal lenses does more than just help correct vision in these cases. They can also prevent possible eye damage and be used to help control vision issues such as myopia. If you want more information on this topic I have an article here for you.
Regardless of whether you need single vision or bifocal lenses, you should know there are many different types of both. After deciding between the two, you will still need to determine the types of lenses that are best for you.
Examples of Single Vision Lenses
While not as complex as bifocal lenses, there are still a few different options available for those choosing single vision lenses. At the most basic level, the two different types of lenses are those for nearsightedness and those for farsightedness. However, there are still more options available. These include:
- Polycarbonate Single Vision Lenses – These light and thin lenses are durable, impact-resistant, and typically have an anti-scratch coating or an anti-reflective coating. They can also block harmful UV radiation to protect the eyes.
- Mid-Index Single Vision Lenses – These lenses are about 15% thinner than traditional plastic while still being lighter. They usually feature both an anti-scratch and anti-reflective coating. This option is often best for those with a higher prescription.
- Polarized Single Vision Lenses – These can be used in sunglasses, protecting your eyes from the sun’s harmful rays while still enhancing your vision.
Since they are simpler than bifocal lenses, single vision lenses tend to be less expensive. However, various factors, including the type of lenses you choose and whether you get an anti-scratch or anti-reflective coating, can change the price of your lenses.
Examples of Bifocal Lenses
As is the case with single vision lenses, bifocal lenses can come in many different materials. However, when choosing bifocal lenses, you will want to begin by deciding on the arrangement of the segments within the lenses. Types of bifocal lenses include:
- Half-Moon Bifocals – Refers to the half-moon shape of the near-vision portion of the lenses, which is rounded on the bottom and flat on top. These are also commonly referred to as Flat-Top or D-Segmented Bifocals.
- Round Segmented Bifocals – Refers to the completely rounded shape of the near-vision portion of the lenses.
- Executive Bifocals – Refers to the near-vision portion of the lenses comprising the entire bottom portion of the lenses. These are also commonly referred to as Franklin Bifocals.
Bifocal lenses are designed so that you look straight ahead and through the topmost portion of the lenses when looking at objects further away. Meanwhile, the near-vision portion of the lenses is at the bottom because you tend to look down at objects 18 inches or less from the eyes.
Other Types of Lenses Explained
Single vision and bifocal lenses are the most common types used by individuals with vision issues. However, they are not the only types of lenses available.
If you are in the process of getting new glasses or getting glasses for the first time, it is good to have information on the many options available to you.
Understanding Trifocal Lenses
Like bifocal lenses, trifocal lenses are for those who have issues seeing both nearby and faraway images. The difference between the two is that trifocal lenses feature three points of focus.
The points of focus in a trifocal lens typically include an area for intermediate vision in addition to areas for distance and near vision. This makes them a great option for those who spend much of their time focusing on objects at an intermediate distance.
An intermediate distance is generally a distance of about 18 to 24 inches away from the eyes. Computers are a good example of objects we typically view at intermediate distances.
Understanding Progressive or “No-Line Bifocal” Lenses
Progressive lenses are sometimes referred to as “no-line bifocals.” However, that name is slightly inaccurate. This is because they are also designed to help those who need assistance with intermediate vision in addition to near and distance vision.
They can really be considered a more advanced form of trifocal lenses. This is because they have a seamless appearance. When looking at progressive lenses, you cannot see any lines where the three different focal areas of the lenses meet.
One of the primary drawbacks of progressive lenses is their cost. While they can be highly beneficial, they can also be upwards of $100-400$ more expensive than traditional bifocal lenses.
Are There Single Vision and Bifocal Contact Lenses?
People opt for contacts over glasses for plenty of reasons. For some, it is a simple matter of aesthetics. Others prefer contacts because it is easier to move around while wearing them.
While both have benefits, unless there is a medical reason not to, you should use whatever feels more comfortable.
Contact Lenses for Multivision Correction
It can actually be a little easier to get the contacts you need if you have issues with both near and distance vision. This is because contacts are generally designed to correct both. If you would typically use bifocals but opt for contacts, these are the two most common options:
- Multifocal Lenses – As with glasses featuring bifocal lenses, these contacts feature multiple areas of focus.
- Monovision Lenses – With these lenses, you wear a contact in your dominant eye to correct your distance vision and another contact in your non-dominant eye to correct your near vision.
Additionally, many people find multifocal contact lenses do not work as well as they grow older, and their vision worsens. The reason is a bigger difference in distance vision compared to the needed reading power. In your prescription, this is described as ADD value. As soon it is higher than 1.75 diopters you tend to lose contrast and glare at night from headlights for example get more noticiable.
Contact Lenses for Single Vision Correction
You may be wondering if you will need different contacts if you only have a problem with either your near or distance vision. This is a good question, as contacts are designed a little bit differently than glasses lenses. If you only need single vision lenses, the same types of contacts are used but in a different way:
- Multifocal Lenses – While these contacts are designed with multiple areas of focus, if you only need your near or distance vision corrected, one area of focus can be set at 0.
- Monovision Lenses – With these contact lenses, you will wear a contact lens in only one eye to correct either your distance or near vision.
If you are uncertain which option is best for you, it is a good idea to speak with your optometrist. They can advise you regarding the options available when it comes to contact lenses.
What Is the Average Cost of Lenses?
It can be tempting to purchase the latest and greatest technology when it comes to lenses. However, the price of a pair of glasses can increase dramatically depending on the type of lenses you choose.
It is important to remember that not every individual will need bifocals. Likewise, while options such as trifocals and progressives are out there, they may not be necessary unless you spend a lot of time on the computer. Keeping this in mind, these are the average prices for different types of lenses.
- Single Vision Lenses – Range from $10 to $300
- Bifocal Lenses – Range from $100 to $400
- Trifocal Lenses – Range from $150 to $500
- Progressive Lenses – Range from $100 to $700
You should also remember you will need to pay an additional charge if you want special features with your glasses lenses. These include anti-reflective, anti-glare coatings, and anti-scratch coatings.
The Average Cost of Contact Lenses
As is the case with glasses, the cost of contact lenses can range greatly depending on many factors. It is important to note that all contact lenses will need replacement at some point, though some need replacement sooner than others. This typically makes contact lenses a more expensive option than glasses on the whole.
If you opt for daily use contacts, you only need to replace them every month to three months on average. This makes them more cost-efficient. You can expect to pay upwards of $150 annually. Do note these contacts require more care.
Meanwhile, daily use contacts, while more convenient, must be changed every day. This means you need to purchase new contacts monthly. Costs can range from $200 to $900 or more annually.
Understanding the Prescription for Your Lenses
Once you have been to an optometrist and decided on the type of lenses best for you, you will receive a prescription for your new lenses. You will need this prescription to purchase your new glasses or contacts.
Understanding the prescription for your lenses can be a little confusing. There are tons of abbreviated terms on a prescription, and all of them refer to different things.
What OD and OS Mean on the Prescription for Your Lenses
Two of the most important abbreviations on a prescription are OD and OS. OD stands for “oculus dexter,” while OS is an abbreviation for “oculus sinister.” That sounds a little odd and perhaps a little scary.
However, this is really just a fancy way optometrists refer to your right and your left eye. OD or oculus dexter refers to your right eye, while OS or oculus sinister refers to your left eye.
You may also see a space on your glasses prescription labeled OU. This is an abbreviation for another fancy Latin phrase, “oculus uterque.” It is used when referring to both eyes at once.
Other Abbreviations on the Prescription for Your Lenses
In addition to OD and OS, you will see various other abbreviations. You do not have to know what they all mean to get your new glasses or contacts. However, it can still be a good idea to have a basic understanding of them.
- SPH – This is short for “Sphere” and indicates the power of the lenses you will need to correct either nearsightedness or farsightedness.
- CYL – This is short for “Cylinder” and shows how much lens power is needed to correct any astigmatism you have.
- AXIS – This shows the angle between two meridians in an eye with astigmatism and is measured in degrees. You must have an AXIS value if you have a CYL value.
- ADD – This indicates the additional magnifying power needed on the bottom part of bifocal lenses. You must have this section filled in if getting bifocals.
- PRISM – This refers to the prismatic power required for the correction of issues with eye alignment. Few prescriptions will have this space filled in.
The power will be indicated with a number along with a plus or minus sign on a prescription. A plus sign (+) indicates you are farsighted, while a minus sign (-) shows you are farsighted. If there is a zero in any space, it means no vision correction is needed in that area.
Understanding a Prescription for Contact Lenses
If you have received a prescription for contact lenses, you may be even more confused. There are even more spaces and even more abbreviations on this type of prescription.
Many of the abbreviations are the same as on a glasses prescription, including SPH, CYL, AXIS, and ADD. They mean the same thing and are measured in the same way. However, a prescription for contact lenses will have additional abbreviations, including:
- BC – Meaning base curve, it refers to the fit necessary for the way your eye curves. It is measured in numbers or with the words flat, median, or steep.
- DIA – This refers to the diameter of the contact lenses needed.
- Dominant – If you are wearing monovision lenses, your dominant and non-dominant eyes need to be identified. They are indicated with a D and N.
Note that you will need to speak with your optometrist in detail before getting your prescription about the type of contact lenses you need. This will ensure you get the right information on your prescription.
Conclusion
The world of eyeglasses and lenses can be a little confusing. This is true whether you are new to wearing glasses or you have been wearing them your entire life. Fortunately, remembering just a few key details can help you easily understand the differences between single vision and bifocal lenses.
Single vision lenses are designed to correct either your near or distance vision but cannot correct both. Bifocal lenses have two focal areas and can correct both your near and distance vision at the same time. Your optometrist will help you decide which option is best for your needs.
