Photochromic vs. Polarised Lenses

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Photochromic vs. Polarised Lenses

Sunglasses are a versatile accessory; they protect your eyes and make you look cool. You may put a lot of thought into the frame of your glasses or sunglasses, but choosing the right lenses is just as important. With so many lenses available, it may be difficult to understand which are right for you. The best lenses for an individual will depend on your unique visual needs and what you hope to get from your shades. Photochromic and polarised lenses are two of the many lens choices which offer excellent UV protection, but many wonder, what exactly is the difference?

What is the difference between photochromic and polarised lenses?

Photochromic and polarised lenses both effectively protect your eyes from harmful UV rays. They’re both available in a diverse range of frame styles and are highly beneficial to wearers. The difference? Simply put, photochromic lenses start clear and darken upon coming into contact with UV light. In contrast, polarised lenses are always tinted and have a special coating that’s especially good at blocking glare.

What are photochromic lenses?

Photochromic lenses, also known as Transitions® lenses, are an excellent choice for people who are sick of switching between their prescription glasses and prescription sunglasses. As light conditions change, so do the lenses. And the best part, you never have to change your frames. Inside, away from UV light, photochromic lenses are clear, but as soon as you step outside and UV rays are present, they gradually darken.

Plastic photochromic lenses and glass photochromic lenses use the same technology but are a bit different in their composition. Plastic photochromic lenses include molecules of silver halide that are usually layered or embedded evenly onto the surface of the lens, providing an even tint when exposed to UV light conditions. Glass photochromic lenses contain the molecules within the glass. This can sometimes cause an irregular tint on lenses with a higher prescription due to the uneven thickness of the lens.

How do photochromic lenses work?

It’s all about a chemical reaction. Photochromic lenses have light-sensitive molecules that shift their structure when combined with UV light. When this light is absorbed, the lenses darken. Away from the UV light, the process reverses, and the lenses become clear again. On average, photochromic lenses darken in 30–60 seconds and clear a bit slower in 2–3 minutes.

The molecules in photochromic lenses are not only sensitive to the presence of UV light but also the amount of it. A lot of UV light and they will change more quickly; less light and they’ll change more slowly. If you find yourself in the shade, you might notice your lenses darkening less than in direct sunlight. UV light is still present in low light, overcast skies, causing photochromic lenses to darken even in these conditions. 

What are polarised lenses?

Polarised lenses are tinted lenses with a special coating that blocks glare, boosts visibility, increases clarity and enhances contrast to make your surroundings more vibrant. Polarised sunglasses are handy for people who spend a lot of time outdoors, as they block out reflections that come from rain, snow, or water. When the sun reflects off these surfaces, it causes a powerful, horizontal glare that may cause eye damage and strain.

How do polarised lenses work?

Polarised lenses are coated in a chemical filter that acts as a vertical blocker and won’t allow any horizontal wavelengths through. When light hits a flat object, like a lake, ski slope, or metal sheet, the reflection is in a single, concentrated direction, creating a bright polarised glare. Polarised glare means the light waves are mostly aligned in one direction, in this case, horizontally. As polarised lenses are designed to block this horizontally polarised light, their chemical filter absorbs it, letting you see clearly.

Advantages and disadvantages of photochromic lenses

One of the biggest advantages is how cost-effective and convenient photochromic lenses can be. With no need for a separate pair, one pair of glasses acts as both your eyeglasses and sunglasses. Photochromic glasses prevent you from worrying about changing your glasses upon entering or exiting a building or the sunshine. Photochromic lenses are beneficial when the weather changes throughout the day; if the sun is going in and out of the clouds, you’re on the slopes or hiking in the woods.

While photochromic glasses benefit many wearers, there are some disadvantages to consider. Temperature impacts the rate at which photochromic lenses darken or clear up. The lenses usually darken more fully in cold weather but take longer to clear. In warmer weather, they may not darken as much but will become clear quicker. Most photochromic lenses perform well for three-plus years, but eventually, they will become less reactive to light conditions and take longer to shift between clear and tinted. 

It is important to note that some photochromic lenses are unsuitable for driving because the car windshield blocks the UV rays that generally cause the lenses to adjust. Some models, including the Transitions XTRActive® lenses, have more photochromic molecules allowing them to transition even while in the car. These lenses always have a very light base tint and will not go as dark in the car as outdoors. 

Advantages and disadvantages of polarised lenses

Whether hiking, cycling, or boating, polarised sunglasses are a great option. The lenses are designed to reduce glare and enhance outdoor vision, helping improve performance while making colours look more vibrant. Polarised lenses are well suited for driving during the day, as glare from other cars, or the road is a common scenario. With reduced glare comes a lower risk of eye strain. Polarised lenses are an excellent solution for people with light sensitivity, and they may even be recommended to patients who have had cataract surgery.

With many advantages, there are some things to consider before buying polarised lenses. Polarised lenses may reduce vision clarity when looking at LCD screens or certain displays. For anyone working in a job where looking at display screens is expected, you should test polarised lenses before purchasing. 

While polarised lenses are beneficial in snowy conditions, they may make it harder to see patches of ice. If you’re skiing, snowboarding, driving, or walking where there might be lots of ice, it may be best to avoid your polarised sunglasses and reach for another pair. Another disadvantage is that polarised lenses are always tinted, so if you wear prescription glasses, you will need to carry your glasses and sunglasses. 

Is photochromic or polarised better?

Photochromic and polarised lenses have distinct qualities and advantages, making them great options for your collection. Generally, neither is considered better than the other. Photochromic lenses are a great option for those who are always on the run, with one pair of glasses serving as eyeglasses and sunglasses. Polarised lenses block out glares and reflections, not only improving vision but providing a level of safety. 

Both lenses will protect your eyes from the sun’s harmful ultraviolet light. The best choice is always individual, so it is encouraged that you review the functionalities, consider your environment and budget, and compare this to your lifestyle. If you still have questions, head to our Optical Centre and speak with one of our opticians. 

Photochromic or polarised lenses, which to buy?

Depending on what you use your sunglasses for, one may be a better choice than the other. If a reduction in glare will benefit your performance in fishing or cycling, for example, you may choose polarised lenses. Photochromic lenses may be best for you if you need a pair of sunglasses for everyday wear.

Lenses don’t have to be complicated; consider the differences and your needs, so you can buy and wear what works for you. With so many options, it’s always best to be informed about your choices. Learn more about lenses, and remember, whether you purchase photochromic or polarised, make sure they fit into frames that make you feel confident.

Ask the Optician

ASK NOW

Photochromic vs. Polarised Lenses

Sunglasses are a versatile accessory; they protect your eyes and make you look cool. You may put a lot of thought into the frame of your glasses or sunglasses, but choosing the right lenses is just as important. With so many lenses available, it may be difficult to understand which are right for you. The best lenses for an individual will depend on your unique visual needs and what you hope to get from your shades. Photochromic and polarised lenses are two of the many lens choices which offer excellent UV protection, but many wonder, what exactly is the difference?

What is the difference between photochromic and polarised lenses?

Photochromic and polarised lenses both effectively protect your eyes from harmful UV rays. They’re both available in a diverse range of frame styles and are highly beneficial to wearers. The difference? Simply put, photochromic lenses start clear and darken upon coming into contact with UV light. In contrast, polarised lenses are always tinted and have a special coating that’s especially good at blocking glare.

What are photochromic lenses?

Photochromic lenses, also known as Transitions® lenses, are an excellent choice for people who are sick of switching between their prescription glasses and prescription sunglasses. As light conditions change, so do the lenses. And the best part, you never have to change your frames. Inside, away from UV light, photochromic lenses are clear, but as soon as you step outside and UV rays are present, they gradually darken.

Plastic photochromic lenses and glass photochromic lenses use the same technology but are a bit different in their composition. Plastic photochromic lenses include molecules of silver halide that are usually layered or embedded evenly onto the surface of the lens, providing an even tint when exposed to UV light conditions. Glass photochromic lenses contain the molecules within the glass. This can sometimes cause an irregular tint on lenses with a higher prescription due to the uneven thickness of the lens.

How do photochromic lenses work?

It’s all about a chemical reaction. Photochromic lenses have light-sensitive molecules that shift their structure when combined with UV light. When this light is absorbed, the lenses darken. Away from the UV light, the process reverses, and the lenses become clear again. On average, photochromic lenses darken in 30–60 seconds and clear a bit slower in 2–3 minutes.

The molecules in photochromic lenses are not only sensitive to the presence of UV light but also the amount of it. A lot of UV light and they will change more quickly; less light and they’ll change more slowly. If you find yourself in the shade, you might notice your lenses darkening less than in direct sunlight. UV light is still present in low light, overcast skies, causing photochromic lenses to darken even in these conditions. 

What are polarised lenses?

Polarised lenses are tinted lenses with a special coating that blocks glare, boosts visibility, increases clarity and enhances contrast to make your surroundings more vibrant. Polarised sunglasses are handy for people who spend a lot of time outdoors, as they block out reflections that come from rain, snow, or water. When the sun reflects off these surfaces, it causes a powerful, horizontal glare that may cause eye damage and strain.

How do polarised lenses work?

Polarised lenses are coated in a chemical filter that acts as a vertical blocker and won’t allow any horizontal wavelengths through. When light hits a flat object, like a lake, ski slope, or metal sheet, the reflection is in a single, concentrated direction, creating a bright polarised glare. Polarised glare means the light waves are mostly aligned in one direction, in this case, horizontally. As polarised lenses are designed to block this horizontally polarised light, their chemical filter absorbs it, letting you see clearly.

Advantages and disadvantages of photochromic lenses

One of the biggest advantages is how cost-effective and convenient photochromic lenses can be. With no need for a separate pair, one pair of glasses acts as both your eyeglasses and sunglasses. Photochromic glasses prevent you from worrying about changing your glasses upon entering or exiting a building or the sunshine. Photochromic lenses are beneficial when the weather changes throughout the day; if the sun is going in and out of the clouds, you’re on the slopes or hiking in the woods.

While photochromic glasses benefit many wearers, there are some disadvantages to consider. Temperature impacts the rate at which photochromic lenses darken or clear up. The lenses usually darken more fully in cold weather but take longer to clear. In warmer weather, they may not darken as much but will become clear quicker. Most photochromic lenses perform well for three-plus years, but eventually, they will become less reactive to light conditions and take longer to shift between clear and tinted. 

It is important to note that some photochromic lenses are unsuitable for driving because the car windshield blocks the UV rays that generally cause the lenses to adjust. Some models, including the Transitions XTRActive® lenses, have more photochromic molecules allowing them to transition even while in the car. These lenses always have a very light base tint and will not go as dark in the car as outdoors. 

Advantages and disadvantages of polarised lenses

Whether hiking, cycling, or boating, polarised sunglasses are a great option. The lenses are designed to reduce glare and enhance outdoor vision, helping improve performance while making colours look more vibrant. Polarised lenses are well suited for driving during the day, as glare from other cars, or the road is a common scenario. With reduced glare comes a lower risk of eye strain. Polarised lenses are an excellent solution for people with light sensitivity, and they may even be recommended to patients who have had cataract surgery.

With many advantages, there are some things to consider before buying polarised lenses. Polarised lenses may reduce vision clarity when looking at LCD screens or certain displays. For anyone working in a job where looking at display screens is expected, you should test polarised lenses before purchasing. 

While polarised lenses are beneficial in snowy conditions, they may make it harder to see patches of ice. If you’re skiing, snowboarding, driving, or walking where there might be lots of ice, it may be best to avoid your polarised sunglasses and reach for another pair. Another disadvantage is that polarised lenses are always tinted, so if you wear prescription glasses, you will need to carry your glasses and sunglasses. 

Is photochromic or polarised better?

Photochromic and polarised lenses have distinct qualities and advantages, making them great options for your collection. Generally, neither is considered better than the other. Photochromic lenses are a great option for those who are always on the run, with one pair of glasses serving as eyeglasses and sunglasses. Polarised lenses block out glares and reflections, not only improving vision but providing a level of safety. 

Both lenses will protect your eyes from the sun’s harmful ultraviolet light. The best choice is always individual, so it is encouraged that you review the functionalities, consider your environment and budget, and compare this to your lifestyle. If you still have questions, head to our Optical Centre and speak with one of our opticians. 

Photochromic or polarised lenses, which to buy?

Depending on what you use your sunglasses for, one may be a better choice than the other. If a reduction in glare will benefit your performance in fishing or cycling, for example, you may choose polarised lenses. Photochromic lenses may be best for you if you need a pair of sunglasses for everyday wear.

Lenses don’t have to be complicated; consider the differences and your needs, so you can buy and wear what works for you. With so many options, it’s always best to be informed about your choices. Learn more about lenses, and remember, whether you purchase photochromic or polarised, make sure they fit into frames that make you feel confident.

Prism Glasses

Ask the Optician

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Prism Glasses

Prism glasses may effectively treat eye conditions such as double vision or other binocular vision difficulties. Our eye movements are controlled by six different muscles in each eye, and if one of these muscles is weak, it could cause eye strain, headaches, or even double vision. 

What are prism lenses?

Prism lenses may be prescribed by eye doctors but do not correct any refractive errors like farsightedness or nearsightedness, as they do not contain any focusing power. Temporary prism lenses, called Fresnel prisms, are made of vinyl and are attached to your eyeglasses. This is an excellent option for those wanting to try prism lenses before getting permanent ones or if your double vision is temporary. More permanent prism lenses are usually made of plastic or glass, are wedge or triangle shaped and are infused into regular lens prescriptions. 

How do prism glasses work?

In order to see clearly, light entering the eye must focus on the retina, the area at the back of the eye where light images are translated and sent to the brain. When your eyes are misaligned, they don’t move accurately together, and images are formed on different parts of the retinas, causing double vision. 

Prism glasses compensate for this misalignment by bending and redirecting the light rays on the retina, aligning and producing a clear image. This bending of light improves eye alignment, helping you to see comfortably and prevent double vision.

Why do people see double?

Double vision, or diplopia, is a condition in which you see two of everything. Any misalignment of the eyes may cause you to see double, making it difficult to judge distances, read and perform everyday tasks. Double vision may signify a more severe problem, so you should speak with your eye doctor if you experience it. 

Prism glasses for double vision

Double vision can sometimes be treated with eye exercises, or your doctor may give you a temporary prism to attach to your glasses. If the temporary prisms help your double vision, prisms may then be added to your prescription lenses. A prism bends the light before it travels through the eye and directs it to the right place on the retina, allowing the brain to fuse the two images together to produce one clear image. 

What do prism glasses look like?

If using temporary prisms, these are typically more visible as they are attached to your glasses. If your eye doctor prescribes prism lenses for long-term use, these prisms will be fused into your regular lenses. They will look the same as before, but the glass on one side might be thicker. If this is a concern, consider a thicker frame to hide it. 

What does a prescription for a prism look like?

Your glasses prescription will show you all of the details on the type of vision you have. Numbers indicate how strong lenses need to be and where they should be positioned within the frame. If there is a number in the ‘PRISM’ portion of your prescription, you have a weak eye muscle that needs correction. The ‘BASE’ section will explain how the prism should be aligned. 

PRISM – diopters measure the amount of prism correction needed (from 0.5PD, 1.0PD, 1.5PD and so on) and indicate how misaligned your eyes are. If the power required is high, it can be split into two since alignment is a function of both eyes. 

BASE– depending on your double vision, the prism is placed vertically or horizontally in one or both lenses. It may be on the outer edge of the lens (Base Out, BO), the inner edge (Base In, BI), or at the top (Base Up, BU) or bottom edge (Base Down, BD).

In the above prescription, between the axis and ADD value, there are the prism specifications. There are two main factors to highlight when you read your prescription with prism lenses:

  1. The first value will be indicated by a number between 0.5 and 5.0. This refers to the amount of prism correction needed. Some specialised labs can also produce prescriptions above 5.0.
  2. This number is then followed by B (base). The base is the part of the lens that will be thicker and indicate the direction of the prism. There is BO (base out), BI (base in), BD (base down) and BU (base up). 

How to order prism glasses online

Ordering prism glasses at SmartBuyGlasses is easy. After choosing the pair that best suits you, select your lenses. First, decide the type (distance, progressive, reading, or non-prescription). You will then be prompted to either fill in your prescription manually, upload it, send it later, or choose from your account. Below are the details for entering manually.

  1. Enter distance corrected under SPH for the left and right eye 
  2. Astigmatism details go under CYL and AXIS
  3. PD* (pupillary distance)
  4. Select ‘add prism’ for a small fee and input the prism correction values 

*PD is necessary to calculate correctly; an incorrect value can cause visual discomfort. You can get the correct measurement at your local optician or calculate it yourself with these easy steps in measuring your PD.

Ask our in-house opticians if you have any doubts about how to read and fill out your prescription online.

Prism lenses for daily life

Double vision can be uncomfortable and prevent you from doing everyday activities. Adding a prism to your lenses can restore your vision and improve your quality of life. With an endless possibility of frame choices and an easy way to enter your prescription online, there is no reason double vision should continue impacting your life. 

Ask the Optician

ASK NOW

Prism Glasses

Prism glasses may effectively treat eye conditions such as double vision or other binocular vision difficulties. Our eye movements are controlled by six different muscles in each eye, and if one of these muscles is weak, it could cause eye strain, headaches, or even double vision. 

What are prism lenses?

Prism lenses may be prescribed by eye doctors but do not correct any refractive errors like farsightedness or nearsightedness, as they do not contain any focusing power. Temporary prism lenses, called Fresnel prisms, are made of vinyl and are attached to your eyeglasses. This is an excellent option for those wanting to try prism lenses before getting permanent ones or if your double vision is temporary. More permanent prism lenses are usually made of plastic or glass, are wedge or triangle shaped and are infused into regular lens prescriptions. 

How do prism glasses work?

In order to see clearly, light entering the eye must focus on the retina, the area at the back of the eye where light images are translated and sent to the brain. When your eyes are misaligned, they don’t move accurately together, and images are formed on different parts of the retinas, causing double vision. 

Prism glasses compensate for this misalignment by bending and redirecting the light rays on the retina, aligning and producing a clear image. This bending of light improves eye alignment, helping you to see comfortably and prevent double vision.

Why do people see double?

Double vision, or diplopia, is a condition in which you see two of everything. Any misalignment of the eyes may cause you to see double, making it difficult to judge distances, read and perform everyday tasks. Double vision may signify a more severe problem, so you should speak with your eye doctor if you experience it. 

Prism glasses for double vision

Double vision can sometimes be treated with eye exercises, or your doctor may give you a temporary prism to attach to your glasses. If the temporary prisms help your double vision, prisms may then be added to your prescription lenses. A prism bends the light before it travels through the eye and directs it to the right place on the retina, allowing the brain to fuse the two images together to produce one clear image. 

What do prism glasses look like?

If using temporary prisms, these are typically more visible as they are attached to your glasses. If your eye doctor prescribes prism lenses for long-term use, these prisms will be fused into your regular lenses. They will look the same as before, but the glass on one side might be thicker. If this is a concern, consider a thicker frame to hide it. 

What does a prescription for a prism look like?

Your glasses prescription will show you all of the details on the type of vision you have. Numbers indicate how strong lenses need to be and where they should be positioned within the frame. If there is a number in the ‘PRISM’ portion of your prescription, you have a weak eye muscle that needs correction. The ‘BASE’ section will explain how the prism should be aligned. 

PRISM – diopters measure the amount of prism correction needed (from 0.5PD, 1.0PD, 1.5PD and so on) and indicate how misaligned your eyes are. If the power required is high, it can be split into two since alignment is a function of both eyes. 

BASE– depending on your double vision, the prism is placed vertically or horizontally in one or both lenses. It may be on the outer edge of the lens (Base Out, BO), the inner edge (Base In, BI), or at the top (Base Up, BU) or bottom edge (Base Down, BD).

In the above prescription, between the axis and ADD value, there are the prism specifications. There are two main factors to highlight when you read your prescription with prism lenses:

  1. The first value will be indicated by a number between 0.5 and 5.0. This refers to the amount of prism correction needed. Some specialised labs can also produce prescriptions above 5.0.
  2. This number is then followed by B (base). The base is the part of the lens that will be thicker and indicate the direction of the prism. There is BO (base out), BI (base in), BD (base down) and BU (base up). 

How to order prism glasses online

Ordering prism glasses at SmartBuyGlasses is easy. After choosing the pair that best suits you, select your lenses. First, decide the type (distance, progressive, reading, or non-prescription). You will then be prompted to either fill in your prescription manually, upload it, send it later, or choose from your account. Below are the details for entering manually.

  1. Enter distance corrected under SPH for the left and right eye 
  2. Astigmatism details go under CYL and AXIS
  3. PD* (pupillary distance)
  4. Select ‘add prism’ for a small fee and input the prism correction values 

*PD is necessary to calculate correctly; an incorrect value can cause visual discomfort. You can get the correct measurement at your local optician or calculate it yourself with these easy steps in measuring your PD.

Ask our in-house opticians if you have any doubts about how to read and fill out your prescription online.

Prism lenses for daily life

Double vision can be uncomfortable and prevent you from doing everyday activities. Adding a prism to your lenses can restore your vision and improve your quality of life. With an endless possibility of frame choices and an easy way to enter your prescription online, there is no reason double vision should continue impacting your life. 

Is there a Difference Between Contact Lens and Glasses Prescription?

Is there a Difference Between Contact Lens and Glasses Prescription?

If your vision needs correction, you may be prescribed a glasses prescription or contact lens prescription. Both help improve your vision, but are glasses prescriptions and contact lens prescriptions the same? A common query is if it’s possible to convert a glasses prescription to a contact lens prescription. Read on to discover the answer to these intriguing questions regarding your prescription.

Are glasses prescriptions and contact lens prescriptions the same?

Even though the prescription for glasses vs contact lens prescription may look similar, they are quite different. Contact lenses and glasses correct refractive errors, such as myopia (finding it difficult to see objects far away), hyperopia (finding it difficult to see objects closeup), astigmatism (when your cornea or lens has a different shape than usual) and presbyopia (a refractive error that makes it hard for older adults to see things up close). 

Since prescription glasses rest slightly in front of your eyes, around 12 millimetres away, and contact lenses sit directly on them, you need two separate tests to determine their unique measurements. This means that the parameters specified on your glasses prescription may often differ from your contact lens prescription.

Prescription for glasses vs contacts: How to read glasses and contact lens prescriptions

After your eye test, you will receive a prescription card determining your specific prescription. Your glasses prescription and contact lens prescription will be provided on two different cards. Once you have these prescriptions, you can shop for your glasses or contact lenses online or in-store.

The key differences between a contact lens and a glasses prescription are shown in the image above. Contact lens prescriptions include certain specifications that are not on your glasses prescription, including: 

  1. Base Curve (BC): This measures the curvature of your lens and is based on your eye shape, measured in millimetres.
  2. Diameter (DIA): This specifies the size of the lens and how the lens fits on your actual eye in terms of width, measured in millimetres.
  3. Lens material: This includes the material of your contact lens, which can be either hydrogel or silicone.
  4. Brand manufacturer: There are thousands of contact lens brands out there, so placing the name of the contact lens brand helps with reordering in the future. The ‘brand’ section specifies the measurements and material.

The power/sph (sphere) indicates the lens power, which can be found on both glasses and contact lens prescriptions. On glasses prescriptions specifically, you can also find the cylinder (Cyl), which indicates the strength of astigmatism and the axis, which represents the orientation of the cylinder.  If you have multifocal lenses, an ‘ADD’ means the additional positive power required for the eyes to focus. The ‘prism’ section helps correct people with double vision, aiding in aligning two images so that only one image can be seen, which can only be found on glasses prescriptions. Furthermore, your contact lens prescription may also include an axis and cylinder if it is a lens for astigmatism or multifocal purposes. 

Can you convert a glasses prescription to a contact lens prescription?

No, it is impossible to convert a glasses prescription to a contact lens prescription directly. Furthermore, you cannot convert a contact lens prescription to a glasses prescription. Doctors can prescribe your contact lens prescription after you have completed a contact lens exam.

Can I use my glasses prescription for contact lenses?

As well as not being able to convert your prescriptions, you cannot use your glasses prescription to work out your contact lens prescription. It is important to note that only some people who wear glasses can also wear contact lenses. Therefore, it is recommended you get an eye test for both prescriptions. 

Are contact lenses or glasses better?

When choosing between contact lenses or glasses, we recommend you consider your lifestyle, comfort and price. For example, eyeglasses require little cleaning and maintenance, as well as not having to physically touch your eyes, helping to avoid the risk of eye infections. However, contact lenses do not fog up, which is useful when playing sports, but they can be more expensive than glasses. We recommend trying glasses and contact lenses to see which suits your lifestyle better.

Where to buy contact lenses and glasses online

You can find affordable glasses or contact lenses online or in-store at your local opticians as long as you have an up-to-date prescription. You can use our online Lens Scanner to reveal your current glasses prescription in minutes. However, if you haven’t had an eye exam in the last two years, we recommend booking an appointment to ensure your prescription is accurate. You will need a separate eye test to determine your contact lens prescription, but often you can get your contact lens exam performed at the same time as your eye exam.

So, whether you prefer to wear contact lenses or glasses, you need to book an up-to-date eye exam to ensure your eyes are healthy. Furthermore, remember that you cannot use the same prescription for your glasses and contact lenses and require two separate tests.

Is there a Difference Between Contact Lens and Glasses Prescription?

If your vision needs correction, you may be prescribed a glasses prescription or contact lens prescription. Both help improve your vision, but are glasses prescriptions and contact lens prescriptions the same? A common query is if it’s possible to convert a glasses prescription to a contact lens prescription. Read on to discover the answer to these intriguing questions regarding your prescription.

Are glasses prescriptions and contact lens prescriptions the same?

Even though the prescription for glasses vs contact lens prescription may look similar, they are quite different. Contact lenses and glasses correct refractive errors, such as myopia (finding it difficult to see objects far away), hyperopia (finding it difficult to see objects closeup), astigmatism (when your cornea or lens has a different shape than usual) and presbyopia (a refractive error that makes it hard for older adults to see things up close). 

Since prescription glasses rest slightly in front of your eyes, around 12 millimetres away, and contact lenses sit directly on them, you need two separate tests to determine their unique measurements. This means that the parameters specified on your glasses prescription may often differ from your contact lens prescription.

Prescription for glasses vs contacts: How to read glasses and contact lens prescriptions

After your eye test, you will receive a prescription card determining your specific prescription. Your glasses prescription and contact lens prescription will be provided on two different cards. Once you have these prescriptions, you can shop for your glasses or contact lenses online or in-store.

The key differences between a contact lens and a glasses prescription are shown in the image above. Contact lens prescriptions include certain specifications that are not on your glasses prescription, including: 

  1. Base Curve (BC): This measures the curvature of your lens and is based on your eye shape, measured in millimetres.
  2. Diameter (DIA): This specifies the size of the lens and how the lens fits on your actual eye in terms of width, measured in millimetres.
  3. Lens material: This includes the material of your contact lens, which can be either hydrogel or silicone.
  4. Brand manufacturer: There are thousands of contact lens brands out there, so placing the name of the contact lens brand helps with reordering in the future. The ‘brand’ section specifies the measurements and material.

The power/sph (sphere) indicates the lens power, which can be found on both glasses and contact lens prescriptions. On glasses prescriptions specifically, you can also find the cylinder (Cyl), which indicates the strength of astigmatism and the axis, which represents the orientation of the cylinder.  If you have multifocal lenses, an ‘ADD’ means the additional positive power required for the eyes to focus. The ‘prism’ section helps correct people with double vision, aiding in aligning two images so that only one image can be seen, which can only be found on glasses prescriptions. Furthermore, your contact lens prescription may also include an axis and cylinder if it is a lens for astigmatism or multifocal purposes. 

Can you convert a glasses prescription to a contact lens prescription?

No, it is impossible to convert a glasses prescription to a contact lens prescription directly. Furthermore, you cannot convert a contact lens prescription to a glasses prescription. Doctors can prescribe your contact lens prescription after you have completed a contact lens exam.

Can I use my glasses prescription for contact lenses?

As well as not being able to convert your prescriptions, you cannot use your glasses prescription to work out your contact lens prescription. It is important to note that only some people who wear glasses can also wear contact lenses. Therefore, it is recommended you get an eye test for both prescriptions. 

Are contact lenses or glasses better?

When choosing between contact lenses or glasses, we recommend you consider your lifestyle, comfort and price. For example, eyeglasses require little cleaning and maintenance, as well as not having to physically touch your eyes, helping to avoid the risk of eye infections. However, contact lenses do not fog up, which is useful when playing sports, but they can be more expensive than glasses. We recommend trying glasses and contact lenses to see which suits your lifestyle better.

Where to buy contact lenses and glasses online

You can find affordable glasses or contact lenses online or in-store at your local opticians as long as you have an up-to-date prescription. You can use our online Lens Scanner to reveal your current glasses prescription in minutes. However, if you haven’t had an eye exam in the last two years, we recommend booking an appointment to ensure your prescription is accurate. You will need a separate eye test to determine your contact lens prescription, but often you can get your contact lens exam performed at the same time as your eye exam.

So, whether you prefer to wear contact lenses or glasses, you need to book an up-to-date eye exam to ensure your eyes are healthy. Furthermore, remember that you cannot use the same prescription for your glasses and contact lenses and require two separate tests.

Ask the Optician

ASK NOW