Key Takeaways
- A glasses prescription and a contact lens prescription are not the same.
- Contacts sit directly on your eye, so they require different measurements than glasses to make them custom for you. The distance that a prescription sits from your eye also impacts the prescription
- Our eye doctor in Kelowna can recommend options for your individual eyes during a contact lens fitting and exam.
You finally got your eyes checked and walked away with a glasses prescription in hand. At Tutt Street Optometry, one of the most common questions we hear is if you can use that glasses prescription to order contacts, too. But we want you to know that a glasses prescription and a contact lens prescription are 2 separate things.
Your glasses prescription cannot be used to order contact lenses, and using the wrong one can affect both your comfort and your vision clarity. Instead, it’s a good idea to start with a proper contact lens fitting and exam.
The Reason the Prescriptions Are Different
The biggest reason these prescriptions differ is how far they are from your eyes. Your glasses sit roughly 12 to 14 millimetres away from your eye, but contact lenses rest directly on the surface of your eye. That small distance changes how light reaches your eye, which means the required lens power is different too.
Because of this, contact lenses require an additional fitting and assessment beyond a standard glasses exam.
An Overview of Each Prescription
What a Glasses Prescription Includes
A glasses prescription includes the optical values the lens maker needs to create glasses that provide clear vision for your daily activities. The sphere measurement indicates the type of vision correction you need, with a minus sign (-) signalling nearsightedness and a plus sign (+) indicating farsightedness.
If you have astigmatism, the cylinder and axis powers tell the lens maker how to correct for it. If you need help with both distance and near vision, an “add” value for reading correction may also appear.
What Makes a Contact Lens Prescription Different
A contact lens prescription includes those same vision correction values, plus a few more that are specific to how a lens fits on your eye. Your contact lens prescription may include:
- Base curve, which helps the lens fit the shape of your eye comfortably
- Diameter, which confirms the lens covers your eye properly without shifting
- A specific brand or lens material, since fit can vary between manufacturers
These details can only be determined during an in-person fitting. No glasses prescription includes them because the glasses don’t sit directly on your eyes. The type of contact lens you end up with, whether soft, daily disposable, or extended wear, can also affect which measurements matter most.
Why the Numbers Can Look Different
If you’ve ever compared your 2 prescriptions side by side and noticed the numbers don’t match, that’s completely normal. For stronger prescriptions, the power values often need to be adjusted when converting to a contact lens. The further a spectacle lens sits from your eye, the more that power shifts.
Cylinder values, which correct for astigmatism, may also change. In some cases, they don’t appear on a contact lens prescription at all. Even small differences in these numbers can affect how clearly you see and how comfortable the lens feels throughout the day.
Can You Convert a Glasses Prescription to Contacts?
Your glasses prescription is just the starting point in determining your contact lens prescription. A contact lens assessment is critical to ensure the lens fit is appropriate.
There must be enough tear flow under the lens to maintain adequate hydration and oxygen supply, but if the lens is too loose, the vision might fluctuate, or the lens could be uncomfortable. It is also important to ensure the prescription in contacts is confirmed so that your eyes aren’t being strained while wearing contact lenses.
The Importance of a Contact Lens Fitting
During a contact lens fitting, the eye doctor places trial lenses on your eyes to confirm the fit, comfort, and vision clarity before finalizing your prescription. This step is especially important if you have astigmatism. Toric lenses, which correct for astigmatism, add an additional layer of complexity as any rotation impacts the success of the fit.
Skipping this step and guessing at your prescription can lead to blurry vision, ocular or visual discomfort, or a poorly fitting lens that puts your cornea in a state of distress.
Our contact lens fittings are personalized to your eyes. Our team takes the time to get to know your life, your preferences, and how you spend your time, so we can recommend lenses that could work for you. For example, if you find contact lenses often feel dry and uncomfortable by the end of the day, our team can recommend options that may be more comfortable for dry or sensitive eyes.
Glasses, Contact Lenses, or Both: What to Choose
There’s no single answer to whether you should wear contacts, glasses, or a little bit of both. Your lifestyle, comfort level, and daily routine all play a role in what works for you. Some people prefer glasses for everyday wear and reach for contacts during sports or social events. Others wear contacts daily and keep glasses as a backup.
Many people find that using both gives them the most flexibility. Our eye doctor in Kelowna can help you figure out which option fits your needs, or whether a combination of both makes the most sense for your life.
Schedule Your Contact Lens Exam
At Tutt Street Optometry, our team is happy to walk you through your prescription options and answer any questions you have about glasses, contacts, or both. If you’re curious about clear vision without glasses, we encourage you to book your contact lens fitting today.
