Base Curve (BC) and Diameter (DIA) - what do they mean?Updated 10 months ago

When you receive a contact lens prescription, two crucial parameters you will encounter are the Base Curve (BC) and the Diameter (DIA). These measurements are essential for ensuring that the contact lenses fit your eyes correctly, providing both comfort and optimal vision.

Please note: Dimple Color lense have a BC of 8.70mm and a DIA of 14.20mm. If your prescription differs from this, please consult your optical professional before purchasing.

Base Curve (BC)

Definition: The Base Curve (BC) refers to the curvature of the back surface of the contact lens. This measurement is tailored to match the curvature of your cornea, the clear front part of your eye.

Importance:

• Fit: The BC ensures that the contact lens sits snugly on the cornea. A lens that is too flat or too steep can cause discomfort, poor vision, or even damage to the eye.
• Comfort: A properly fitted base curve helps maintain lens stability and comfort throughout the day.
• Oxygen Permeability: The fit influenced by the base curve also affects how well the lens allows oxygen to reach the cornea, which is vital for eye health.

Typical Values: The BC is measured in millimeters (mm) and usually ranges from about 8.0 mm to 10.0 mm. Common base curves are around 8.6 mm to 8.8 mm.

Diameter (DIA)

Definition: The Diameter (DIA) of a contact lens is the measurement of its overall width from edge to edge. This measurement ensures that the lens covers the correct portion of your eye.

Importance:

• Coverage: The DIA ensures the lens covers the cornea adequately without extending too far onto the sclera (the white part of the eye) or being too small to cover the entire cornea.
• Comfort: Proper diameter helps maintain comfort and stability, preventing the lens from moving excessively or causing irritation.
• Peripheral Vision: An appropriate diameter ensures that your peripheral vision remains clear and unobstructed by the edge of the lens.

Typical Values: The DIA is also measured in millimeters (mm) and usually ranges from about 13.0 mm to 15.0 mm. Common diameters are around 14.0 mm to 14.5 mm.