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Contact Lenses | Optical Center SmartBuyGlasses CA

Are My Glasses And Contact Lens Prescription The Same?  


It is logical to jump to the conclusion that your glasses prescription and contact lens prescription would be exactly the same. This could prove useful if switching between the two options. But unlucky for you, they are not at all the same. You will need to have a different type of eye exam to reveal your contact lens prescription compared to your glasses prescription.

Here you can find out what goes on in the appointment with the optician to find each prescription, and you can also discover how to read and understand your prescription. It is the law for an optician to give you a document with your prescription detailed on it after an eye exam, so you should definitely be able to obtain one.

The primary difference between the contact lens and glasses prescriptions is the eye exam. The procedure and prescription result varies because a glasses prescription is designed for vision support that sits a certain distance away from your eyes, usually about 12 millimetres. On the other hand, a contact lens prescription has to correct your vision while in direct contact with the surface of your eye. As you may know, vision is all about the point that rays of light converge on the retina. The glasses or contact lenses are the tools used to alter this point. The distance they are from your eye will therefore change the point at which the rays cross. It is easy to picture this theory using a magnifying glass. The image you see through it will be very different when held up close to your eye compared to holding the magnifying glass at arm’s length.


Eye Test for Prescription Glasses


When you have an eye test carried out for eyeglasses, the optician will measure three things.


  1. SPH: this refers to the lens power. It is important for correcting refractive errors, which is crucial for those with nearsightedness (myopia) and farsightedness (hyperopia). Such errors are measured in diopters (D for short). 

  2. AXIS: the axis is used for more complex problems like astigmatism. It measures the shape of the lens, which is needed in order to correct non-spherical corneas, which is what causes astigmatism.

  3. ADD: these measurements can be optional as they are only relevant for those looking for specialised lenses like multifocals. The ADD represents the addition and dominant measurements, which are noted for each individual eye (OD right eye and OS left eye).


How to Read Your Glasses Prescription


No matter your visual impairment, your prescription is unique to your eyes only.


The first section features a figure for OD and OS - your right and left eye. The figures will start with a plus or minus symbol. The minus means you have a negative power, and are farsighted. This means you can see things that are further away, but can’t read text in front of you. If there is a plus by the number, you have a positive power and are nearsighted. So you can clearly see nearby objects but struggle to see in the distance. The strength of your prescription is determined by how big these numbers are: the higher the number the stronger the prescription. 


You will also find information about your SPH, which is the lens power assigned to correct your visual needs.


Next, you can take a look at the Cylinder (CYL). A figure will only appear here if you have astigmatism strong enough to need correcting.


You will also see the AXIS - a number between 1 and 180 that defines the lens meridian for both vertical and horizontal axes.


If you are going for multifocal lenses to correct presbyopia, you will find the ADD. This is the magnifying power, which will be equal for both eyes, and usually ranges between +0.75 and +3.00.


Finally, you will see your pupillary distance (PD): the space between your pupils in millimetres.


Eye Test for Prescription Contact Lenses


The eye test for contacts will follow the same processes as one for glasses, but it will measure a few extra things too. For example, you should be able to find your base curve, which looks at the shape of your lenses. You should also discover the diameter of the lenses. This is to make sure that the size and shape of the contact lens fits with the size and shape of your eye. Once you receive your prescription, you need to note the brand of contact lenses and expiration date. Note that the prescription powers for contact lenses will be different to your glasses prescription.


Another difference between prescriptions for glasses and contact lenses is that if you don’t need any kind of corrective power in the lenses, you can buy non prescription glasses for aesthetic purposes without a prescription. However, if you want contact lenses despite not having any visual impairments, if you want coloured contacts for example, you will still need a prescription. This is because contact lenses are a medical device that cannot be used by anyone and everyone. You therefore need to get an eye test from an optician to get any type of contact lens. To ensure yours is accurate, it is advisable to get an eye test every two years.


How to Read Your Contact Lens Prescription


Unlike with glasses, a contact lens prescription will have a section dedicated to BC, which stands for Base Curve. This measurement tends to fall between the numbers of 8 and 10.


You will also find the diameter DIA of the contact lenses. This usually varies between 13 and 15mm.


Everything else will be the same as what you see on a glasses prescription, but the figures themselves will be different to your glasses prescription because of where the contacts are located on your eye. You will however see a section for colour in case your lenses are tinted or coloured, and the optician will usually specify a brand of contact lenses that they recommend for your particular needs. 


Remember that unlike glasses prescriptions, contact lenses have an expiration date. The prescription will become invalid after one or two years, and you will need to get retested. You cannot buy contact lenses without a formal prescription, so it is important to get an eye exam regularly. 


For extra help on which contact lenses are right for you, take a look at this helpful guide.


Got Your Prescription? Buy Prescription Glasses Online


Now for the fun stuff - go shopping! SmartBuyGlasses has an enormous range of online prescription glasses and contact lenses. You can find the top designer brands like Ray-Ban prescription glasses and Oakley prescription glasses, and you can browse our range of contact lenses too. For more budget friendly options without compromising on style, take a peek at the SmartBuy Collection and Arise Collective for cheap prescription glasses. There are all sorts of frame styles at super friendly prices. 


Once you have chosen your glasses or contact lenses, you can upload your contact lens or glasses prescription online, or email it to us later. Then you can choose the type of lens you need, such as Arise HD Clarity Prescription lenses. These come with UV protection, a scratch and impact resistant coating, and are aspheric, meaning they are thinner and lighter than traditional lenses. At this stage, you can add other optional coatings like blue light block or colour tints. Then all you have to do is head to the checkout and wait for that confirmation email to fly into your inbox, and then receive your glasses or contacts through the post. Prescription glasses Canada only take a few days to arrive, and will be ready to wear straight away. It really couldn’t be easier. 

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