What are contact lenses that have a non-spherical back surface called?

Contact lenses that feature a non-spherical back surface are referred to as aspheric lenses. This design allows for a more gradual change in curvature compared to spherical lenses, which have a uniform curvature throughout. The non-spherical shape of aspheric lenses helps in reducing optical aberrations and can improve visual acuity, especially for individuals with higher degrees of astigmatism or those who require precise vision corrections.

Additionally, aspheric lenses can enhance comfort and stability on the eye, making them a favored choice for many patients. By offering a smoother transition between different powers, these lenses also support visual demands across varying distances, which can be particularly beneficial for individuals with presbyopia or those who need multifocal corrections.

In contrast, other types of lenses, like regular, spherical, or multifocal lenses, may not possess the same advantages tied to the aspheric design. Regular lenses typically refer to lenses without any significant specialized design features, spherical lenses maintain a consistent curvature, and multifocal lenses incorporate different focal zones within the same lens but do not inherently feature the non-spherical back surface characteristic of aspheric lenses.