What is described as the single curve on the front surface of a lens?

The base curve refers to the primary curvature that exists on the front surface of a lens. This curve is fundamental in determining how light is refracted as it passes through the lens, making it crucial for achieving the desired visual correction and comfort for the wearer.

By shaping the base curve appropriately, lens designers can influence various optical properties, such as magnification and distortion, which ultimately affect visual acuity. It is essential in ensuring that the lens fits well with the laws of optics, providing a smooth transition for light entering the eye.

Understanding the base curve is particularly important for fitting contact lenses and creating eyewear, as it helps provide a proper alignment of the lens with the cornea, thereby maximizing comfort and effectiveness. The other curves, such as peripheral or refractive curves, serve specific roles but do not define the single primary curvature of a lens in the same way the base curve does.