At which reference point should a bifocal be fitted for a first-time wearer?

For a first-time wearer of bifocal lenses, the correct reference point for fitting is the lower lid margin. This fitting point is important because it ensures that when the wearer looks straight ahead, the distance portion of the lenses provides optimal vision while the near portion is correctly positioned for reading or close work.

Positioning the bifocals at the lower lid margin allows the wearer to comfortably transition their gaze between the two sections of the lens without significant adjustment. It helps in reducing any potential distortion or discomfort when looking down, as the near vision area will be aligned with the line of sight during typical reading activities, which usually occurs below the horizontal gaze.

Although the other options may have relevance in specific contexts, they do not provide the most effective positioning for bifocals on a first-time wearer. For example, mid-pupil placement may work for other types of lenses or well-experienced users, but it does not cater to the unique needs of someone new to bifocals. Similarly, fitting the lens at the top of the nose or the optical center does not align with the functional requirements of bifocals, as these placements can lead to problems like difficulty seeing nearby objects or a misalignment with the primary viewing areas.