The Importance of BC in Contact Lenses

The Importance of BC in Contact Lenses

When it comes to choosing contact lenses, many people tend to focus on the prescription (Power), such as -2.00, -6.50, or values for farsightedness or astigmatism. However, one important factor that’s often overlooked is the BC (Base Curve) , the curvature of the lens which plays a key role in long-term comfort and eye health.

What is BC?

BC, or Base Curve, is the curvature of the back surface of a contact lens, measured in millimeters (mm). It determines how well the lens conforms to the shape of your cornea.

  • Lower BC (e.g. 8.3 or 8.4 mm): steeper curve, for more curved corneas
  • Higher BC (e.g. 8.7 or 9.0 mm): flatter curve, for flatter corneas

Why is BC important?

  • Proper lens fit
     If the lens is too tight (low BC), it may restrict blood and oxygen flow.
     If it’s too loose (high BC), it can move too much and affect vision clarity.
  • Comfort throughout the day
     A well-fitting lens feels natural and comfortable, even with extended wear.
  • Reduced risk of eye health issues
     An incorrect BC can lead to corneal abrasions, infections, or chronic dry eyes.
  • Stable and clear vision
     A properly fitted lens stays in place and provides consistent, sharp vision.

BC Options from Ta-To.com

Acuvue

Bausch + Lomb

How do you know your BC?

You can’t guess your BC when ordering contact lenses online. It should be measured by an eye care professional using specialized tools like a keratometer or a corneal topographer to precisely map the shape and curve of your cornea.

Choosing the right contact lenses isn’t just about power. BC is just as important because it affects your comfort, safety, and visual clarity. If you’re unsure of your BC, be sure to get your eyes measured by a professional before making a purchase.

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