Revisiting the conoid of sturm.

摘要

There are several ways to achieve pseudoaccommodative multifocal vision, but all share one element: At distance, near, or both, some of the light is not focused on the retina. Depth of focus is achieved at the expense of sharpness of vision.What are the ways to achieve pseudoaccommodative multifocal vision? They include myopic astigmatism, coma or other higher-order aberrations (HOAs), bifocal and multifocal optics, and pinhole vision. All these approaches must be distinguished from a system in which true accommodation occurs; the latter is characterized by the ability to adjust the focal length of the optical system to provide a sharp image at distance, intermediate, and near.