Understanding Base Curve (BC) and Diameter (DIA) Specifications in Contact Lens Prescriptions
Base curve (BC) and diameter (DIA) are crucial parameters in contact lens prescriptions that ensure the lenses fit your eyes comfortably and properly. These measurements are determined by your eye doctor during your eye exam and have specific implications when selecting lenses. Below, we explain the key points and address common questions about BC and DIA specifications.
Why Are Base Curve and Diameter Important?
Base curve (BC) measures the curvature of the inner surface of the contact lens, while diameter (DIA) defines the total width of the lens. These parameters are essential to the fit and comfort of the lenses, as they must properly align with the shape of your eye.
Can I Change Base Curve or Diameter?
No, base curve and diameter are fixed by the manufacturer for each specific contact lens brand and model. These values cannot be overridden or manually adjusted when ordering lenses.
We can only process the order with the exact brand that the doctor provided you with and its specific base curve and diameter.
Fixed Parameters Across Brands
Each contact lens brand has its own standard BC and DIA values, which are not adjustable unless the manufacturer produces the lenses with two base curve options. The DIA is always standard no matter how many options are available for the base curve.
For example, the Dailies Total 1 lenses are manufactured with a standard BC of 8.7 and a DIA of 14.1, while the Acuvue Oasys 1 Day with Hydraluxe lenses are manufactured with a BC of 8.5 or 9.0 and a standard DIA of 14.3.
Do BC and DIA Need to Match Exactly Between Brands?
Yes, BC and DIA must match the values specified in your prescription. If switching between brands, differences in BC and DIA can impact both the fit and comfort of the lenses. You should consult your eye doctor before changing brands to confirm compatibility.
What Should I Do if I Can’t Find a Brand with the Same BC and DIA as My Prescription?
In this case, it is possible you are either looking at the wrong brand or the doctor might have written the incorrect information on the prescription.
Key Points to Remember
BC and DIA are manufacturer-defined and cannot be modified.
Consult your prescribing eye doctor before switching to a new lens brand with different specifications.
Trial lenses are highly recommended to confirm fit, particularly if BC/DIA specifications differ slightly between brands.
By understanding the importance of BC and DIA and consulting your eye doctor when necessary, you can ensure proper fit and comfort for your contact lenses.