What does the term "trifocal" refer to in optical lenses?

The term "trifocal" specifically refers to lenses that incorporate three distinct optical powers, allowing for vision correction at different distances: distance, intermediate, and near vision. A trifocal lens typically has three separate zones visible on the lens surface, each designed for specific visual tasks. The upper portion of the lens is focused for distance vision, the middle part is tailored for intermediate vision (such as viewing a computer screen), and the lower segment is for near vision (like reading).

This design caters to the needs of individuals who have presbyopia or similar vision issues, providing a seamless transition between the different visual fields without the need to switch between multiple pairs of glasses. Each section of the lens is clearly defined, enabling the wearer to see clearly at varying distances without the need for additional optical devices.