Buying contact lenses online allows you the convenience of never having to leave you home while getting your contact lenses at the best price possible. But if you don’t know how to buy contact lenses online you could be missing out on all the benefits.
Even if you think you know how to buy contact lenses online or you’ve done it before, I would still recommend reading through this article. You may be surprised to find that you’ve been doing it wrong!
In this article I’ll discuss 3 crucial step to buying contact lenses online.
1. Getting The Right Numbers
2. Getting The Right Price
3. Getting the Right Parameters
Let’s get right into the first one.
1. Getting The Right Numbers
We all know that to buy contact lenses online or elsewhere you need a prescription. And we all know that to get a prescription we go the eye doctor. However, what some people don’t know is that by default the eye doctor will write you a prescription for glasses, not for contact lenses and the two are not the same thing!
Generally speaking, unless you’ve paid extra for a contact lens assessment (A.K.A contact lens fitting, contact lens exam, contact lens check, etc.) you will not walk out of your eye doctor’s office with a contact lens prescription.
If you order your contact lenses using the numbers found on your glasses prescription, there is a high likelihood that you will not get the proper contact lenses. Doing so can lead to blurry vision and eyestrain when wearing your contact lenses.
How Get a Contact Lens Prescription
The best way is to ask your eye doctor for one. Unfortunately, most of the time you will be charged for this. The justification for this is that your eye doctor needs to spend time to assess your vision and the fit of the contact lenses on your eyes. If needed, your doctor can select different contact lens parameters to achieve a better fit.
A note about this: If you’ve paid your eye doctor for a contact lens assessment he/she is required to give you a physical copy of your contact lens prescription. Some unscrupulous eye doctors may attempt to withhold the prescription to have you believe that your only option to purchase your contact lenses is through them. This is illegal!
Converting Your Glasses Prescription to Contact Lenses
The main reason why a prescription for glasses is not the same as a prescription for contact lenses is because of the power conversion that needs to occur for certain prescriptions.
An abridged version of the conversion process goes like this:
1. Converting the ‘Sphere’ number
If the sphere number on your glasses prescription less than or equal to -4.00, no conversion is necessary between glasses and contact lenses.
If the sphere number on your glasses prescription is -4.25 or higher, it will need to be adjusted. Adjustments are made based on a formula, which is summarized in the follow chart.
2. Converting the ‘Cylinder’ number
If the ‘Cylinder’ number on the glasses prescription is -0.25, it is dropped and it not carried through into the contact lens prescription.
If the ‘Cylinder’ number on the glasses prescription is -0.50, it is also dropped from the contact lens prescription, but an additional -0.25 is added to the converted ‘Sphere’ value.
If the ‘Cylinder’ number on the glasses prescription is -0.75 or higher, it is carried through to the contact lens prescription but rounded to the nearest available ‘Cylinder’ power available for contact lenses. The available ‘Cylinder’ powers in contact lenses are usually -0.75, -1.25, -1.75, -2.25, and -2.75.
3. Converting the ‘Axis’ number
If it has been determined that there will be ‘Cylinder’ in the contact lens prescription, the ‘Axis’ on the glasses prescription is carried through to the contact lens prescription. From there it is rounded to the nearest 10 (with exception of ‘Axis’ values of 1-4, which are changed to 180, not 0).
If there is no ‘Cylinder’ in the contact lens prescription, there will also be no ‘Axis’.
There’s a little more to it than that…
The description above of the conversion process from glasses to contact lenses is oversimplified in many ways. I have written in depth explanations of each step of the process for student opticians and optometrists, para-optometric assistants, contact lens fitters, etc.
All the material I’ve written on the topic can be found in Contacts Advice’s Conversion Resources.
2. Getting The Right Price
This is the most critical step that most people skip.
You do not know how to order contact lenses online properly if you’re not consulting a contact lens price comparison website before making your purchase.
Most people only know 1 or maybe 2 websites that sell contact lenses and assume that the website they know is the best place to purchase contact lenses online. This could not be more wrong!
Often, the most popular and well know contact lens websites are the most expensive!
In reality, there is no one contact lenses website that has the lowest price for every brand. Some site have the lowest price for certain brands, and other sites have the lowest price for other brands.
That is why it is an essential step to consult a contact lens price comparison website like Contacts Advice before you purchase contact lenses online.
Contacts Advice
Did You Know?
Prices for contact lenses fluctuate from week to week and from website to website. This means that most people overpay for their already expensive contact lenses.
Contacts Advice compares the price of contact lenses across 10 different websites to undercover the lowest price for every brand.
By consulting Contacts Advice before purchasing your contact lenses you are sure to be paying the absolutely lowest price for your contact lenses!
Use the yellow buttons on the left to look up the lowest price for your brand, or head to ContactsAdvice.com/Lowest-Prices
3. Getting The Parameters
When you’ve found the lowest price for your contact lenses, it’s time to plug in all the numbers and actually put your order through.
Get the Right Brand
Hundred of different contact lens brands exist and some of them differ from each other by one 1 word. If you overlook this you might accidentally be ordering the wrong brand.
Brands for Astigmatism (Toric)
Often, the only thing that differentiates a brand of contact lenses that for astigmatism and one that is not is the word ‘toric’ or the words ‘for astigmatism’. Do not overlook this. Here are some common examples:
| Regular Version | Version for Astigmatism |
| Biofinity | Biofinity Toric |
| MyDay | MyDay Toric |
| ULTRA | ULTRA for Astigmatism |
| Acuvue Oasys | Acuvue Oasys for Astigmatism |
Multifocal Brands
The same is for multifocal contact lenses. A single word often differentiates the regular brand from the multifocal version. Multifocal contact lenses will either contact the terms ‘multifocal’ or ‘for presbyopia’. For example:
| Regular Version | Multifocal Version |
| Biofinity | Biofinity Multifocal |
| Air Optix Aqua | Air Optix Multifocal |
| ULTRA | ULTRA for Presbyopia |
| Biotrue ONEday | Biotrue ONEday for Presbyopia |
Watch the Signs
Signs are crucial when it comes to prescriptions for glasses and contact lenses. Be very careful and look for the plus or minus sign.
If your prescription for contact lenses is hand written, take a second look to make sure the sign is actually what you think it is. Sometimes doctors’ writing can be sloppy and signs can overlap with the numbers making it very difficult to tell what it is.
One last thing to keep in mind about the signs is that they are not always the same for both eyes. Although it’s less common, one eye can have a + while the other eye has a -.
Know the Fields
Depending on who issued your contact lens prescription, sometimes the fields may be slightly different than what you see on the website. Here is an example:
The Sphere/Power
Every glasses prescription has a field for the ‘Sphere’. Contact lens prescriptions will also most likely contact this field, but on most contact lens websites they refer to this field as the ‘Power’ not the ‘Sphere’. The ‘Power’ and the ‘Sphere’ are essentially the same value.
Abbreviation
Abbreviation are very commonly used both contact lens prescriptions and on contact lens websites. Here are some you are likely to encounter.
| Term | Abbreviation |
| Power | PWR |
| Sphere | SPH |
| Cylinder | CYL |
| Axis | N/A |
| Base Curve | BC |
| Diameter | DIA |
| Add | N/A |
Latin Abbreviation
As if abbreviation of English words wasn’t enough, abbreviations of Latin words can also creep into contact lens prescriptions. The most common example of this are the abbreviations for the Latin words for the right and the left eyes.
| English Term | Latin Term | Latin Abbreviation |
| Right Eye | Oculus Dextrus | OD |
| Left Eye | Oculus Sinister | OS |
Summary
If you’ve read through this entire article, you are now know exactly how to order contact lenses online! With all the different contact lens websites out there nowadays, it may seem daunting to search through all of them in order to make sure you’re getting the lowest price. But don’t worry, that’s what Contacts Advice is for!
Did You Know?
Prices for contact lenses fluctuate from week to week and from website to website. This means that most people overpay for their already expensive contact lenses.
Contacts Advice compares the price of contact lenses across 10 different websites to undercover the lowest price for every brand.
By consulting Contacts Advice before purchasing your contact lenses you are sure to be paying the absolutely lowest price for your contact lenses!
Use the yellow buttons on the left to look up the lowest price for your brand, or head to ContactsAdvice.com/Lowest-Prices
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