How should the top of a bifocal segment be fitted according to most opticians?

Fitting the top of a bifocal segment at the level of the lower eyelid margin is a common practice among opticians to optimize function and comfort for the wearer. This positioning allows for an effective transition from the distance vision portion of the lens to the near vision segment. When the bifocal segment is aligned with the lower eyelid margin, it ensures that the wearer can see clearly at near while maintaining a natural line of sight.

This alignment also takes into account the natural position of the eye and the typical movement patterns of the head and eyes when focusing on different distances. Positioning the segment higher may require the wearer to tilt their head to see through the bifocal section effectively, which can lead to discomfort and visual strain. Conversely, positioning it lower may make it difficult for the wearer to engage in near tasks without excessive downward gaze.

Thus, placing the top of the bifocal segment at the lower eyelid margin generally provides the best balance between aesthetics and functional vision, ensuring that the segments are accessible and usable without compromising the overall visual experience.