What type of lens has its peripheral portion flattened to reduce weight and edge thickness?

The positive lenticular lens is designed specifically for reducing weight and edge thickness, particularly in high prescription cases. It consists of a central portion with a stronger curvature that provides the necessary optical power, while the peripheral portion is flattened. This design minimizes the lens's overall weight and thickness at the edges, making it more comfortable for the wearer and aesthetically pleasing by reducing the bulging effect typical of thick lenses. This is particularly beneficial for individuals with higher prescriptions, as it helps to counteract the undesired thickness seen in traditional biconvex lenses, providing a balance between visual correction and comfort.

In contrast, concave lenses typically diverge light rays and are used for myopia, but they do not incorporate the unique design characteristics of lenticular lenses. The standard biconvex lens has uniform curvature throughout which can result in greater thickness, especially at the edges for strong prescriptions. Negative lenticular lenses, as the name implies, would have a different application, typically for diverging light rather than providing a positive magnifying effect. Therefore, the characteristics of the positive lenticular lens make it the most suitable answer for the question regarding reducing weight and edge thickness.