Contact lenses are a convenient way to correct your vision, but getting the right fit is crucial for both comfort and eye health. One of the most important measurements on your contact lens prescription is the base curve, or BC.
So, what does BC mean on contact lenses? The base curve refers to the back curvature of the lens, measured in millimeters (mm). It’s vital for ensuring the lens properly fits the curve of your cornea.
This article will explain everything you need to know about BC, why it matters for comfort and vision, and how to make sure your contact lenses fit just right.
What Does Base Curve (BC) Mean on Contact Lenses?
When you’re shopping for contact lenses, you’ll see “BC” listed on the box or prescription. But what does it mean?
The base curve (BC) is a measurement of the curvature on the inside of the lens. It tells you how well the lens will fit against the surface of your eye, also known as the cornea.
If your cornea is on the steep side, you’ll need a steeper lens with a lower numerical value. If your cornea is flatter, you’ll need a flatter lens with a higher numerical value.
Think of it like shoe shopping: If your shoes are too tight or too loose, they’re going to be uncomfortable.
Why is the right fit so important?
A well-fitted base curve will ensure your contact lenses are comfortable, your vision is clear, and your eyes stay healthy. When the BC is correct, your cornea will get the right amount of oxygen.
If the base curve is off, you might feel some discomfort or irritation. Your eyes might get red or dry, and you could even develop an infection.
Base Curve Values: What’s Normal?
The base curve measurement is a critical factor in ensuring your contact lenses fit correctly. Here’s a quick guide to what’s considered “normal”:
Typical Range for Soft Contact Lenses
For soft contacts, the base curve usually falls somewhere between 8.0mm and 9.0mm. Most people (around 98%) find that a BC in the 8.4-8.6 mm range works well.
The average base curve is often around 8.6mm.
Rigid Gas Permeable (RGP) Lenses
RGP lenses, which are more rigid, have a BC range from 7.0mm to 9.0mm. Because of their firmness, these lenses require a precise fit determined by your eye doctor.
BC Can Vary Between Brands
Keep in mind that the BC can differ from one brand to another. It’s super important to use the specific BC that your eye care professional has prescribed for the brand you’re using.
How to determine your base curve
So, how do you know what base curve you need?
The role of the eye exam
During a comprehensive eye exam, an eye doctor will measure the curvature of your cornea. This measurement is then used to figure out the right base curve for your contact lenses. It’s a crucial step!
Using a keratometer
A keratometer is the tool your eye doctor will use. It’s designed to precisely measure the curve of your cornea, giving your doctor the data they need to find lenses that fit comfortably and correctly.
The contact lens prescription
A valid contact lens prescription will always include the base curve (BC), the lens power needed to correct your vision, and the diameter (DIA) of the lens.
It’s super important to remember: never buy contact lenses without a current, valid prescription from your eye doctor. Wearing the wrong lenses can be uncomfortable and even harmful to your eyes!
What happens if your contacts have the wrong base curve?
Wearing contacts with the wrong base curve can cause several problems:
- Discomfort and irritation. If the base curve isn’t right, your lenses might feel too tight or too loose. This can cause discomfort, redness, and irritation.
- Blurry vision. An incorrect base curve can also affect your vision. Your lenses may not align with the center of your eye.
- Eye damage. Over time, wearing lenses with an incorrect base curve can damage your cornea. This can raise your risk of infection.
- Reduced oxygen. If your lenses don’t fit properly, they might restrict oxygen flow to your cornea, causing dryness and new blood vessel growth.
Frequently Asked Questions (FAQs) About Base Curve
How often should I have my BC re-evaluated?
Regular eye exams are super important! You need to make sure your BC is still a good fit. Your cornea can actually change shape over time, so don’t skip those appointments!
Can I change my contact lens BC without consulting an optometrist?
Definitely don’t do that! It’s not a good idea to mess with your BC without talking to a pro. An eye doctor can really assess the fit and make sure everything’s cool before you switch things up.
What if I experience discomfort with my current lenses?
If your contacts are bugging you, see your eye doctor ASAP. They can check the fit and figure out what’s going on. Don’t just tough it out – get it checked!
Final Thoughts
When it comes to comfortable, healthy contact lens wear, the base curve (BC) is a critical factor. Don’t guess when it comes to the health of your eyes!
To get the right BC for your contact lenses, it’s essential to consult with a qualified eye care professional. They will measure your eye and provide you with an accurate prescription.
Finally, be sure to schedule regular eye exams. Your eye doctor will confirm that your contacts still fit well and watch out for any potential complications.