Which of the following is not a primary type of bifocal contact lens?

Bifocal contact lenses are designed to provide vision correction for individuals who require assistance with both near and distance vision, typically for those experiencing presbyopia. Among the primary types of bifocal contact lenses, concentric, segmented, and annular designs are widely recognized and utilized in clinical practice.

Concentric bifocal lenses feature alternating zones of differing power arranged in concentric circles, allowing the wearer to transition between near and distance vision based on their gaze direction. Segmented bifocal lenses mimic traditional bifocal glasses by incorporating a distinct segment for near vision at the bottom of the lens. Annular lenses provide a continuous zone blending both vision corrections, enhancing the transitional experience without noticeable demarcation.

The term in question, angular, does not refer to a type of bifocal contact lens in the standard terminology used in optics and ophthalmology. Thus, it correctly stands out as not being recognized as a primary type of bifocal design, reinforcing its classification as the correct answer to the question.