What line intersects the mechanical center of a lens pattern horizontally?

The correct answer is the mounting line. This line is crucial in the optical industry as it defines the horizontal point where the lenses will be mounted within a frame. The mounting line assists opticians in aligning the lenses properly within the desired frame, ensuring that the optical centers of the lenses are correctly positioned in front of the wearer's eyes. Proper alignment following this line is essential for providing optimal visual clarity and comfort.

In the context of lens manufacturing and fitting, the mounting line relates directly to how the lens will be positioned when mounted in eyewear. It plays an important role in ensuring that the lenses provide the intended optical performance and that the wearer has an accurate field of vision.

Other options, while related to lenses and optics, do not specifically refer to the horizontal intersection at the mechanical center of a lens pattern. The axis line typically describes the orientation of cylindrical lenses, the reference line is used for various dimensions in lens fabrication, and the centering line may refer to the vertical alignment in a lens pattern. Hence, the mounting line is the most precise answer relating to the horizontal intersection at the lens's mechanical center.