BC in contact lenses means base curve — the curvature of the back of the lens. It matters because it affects how well the lens fits your eye and how comfortable it feels.

What it means

  • A lower BC number usually means a steeper curve.
  • A higher BC number usually means a flatter curve.
  • The right BC helps the lens sit properly on your eye for comfort and fit.

In practice

If your prescription or box shows something like BC 8.6 , that is the lens’s base curve in millimeters. Contact lens brands often offer a small range of BC values, and the best one is chosen to match your eye shape.

If you want, I can also explain the other contact lens abbreviations like DIA, SPH, CYL, and AXIS.