Most aspheric surfaces are primarily manufactured through which method?

Aspheric lenses are designed to have varying curvature across their surface, which helps reduce optical aberrations and provides a better quality of vision, especially in higher prescriptions. The primary method of manufacturing aspheric surfaces is through casting in molds. This process allows for precise control over the curvature and shape of the lens surface, enabling the production of complex geometries that define aspheric designs.

Casting in molds involves using a liquid material that is poured into a pre-formed mold, which captures the desired aspheric shape as it hardens. This technique is particularly effective because it enables mass production while maintaining high accuracy and consistency, essential for the optical performance of the lenses.

The other options, such as cylindrical and spherical surfaces, refer to different types of lens shapes and do not specifically pertain to the aspheric properties. Glass does not denote a manufacturing method; while glass lenses can be made aspheric, the term itself does not relate to how they are created.