In what situation should separate heights be discussed with a wearer?

Separate heights should be discussed with a wearer when there is a consistent difference in eye positioning because it significantly affects how lenses will perform for the individual. When the eyes are not aligned in a standard position, such as one eye being lower or higher than the other, it necessitates the need for separate measurements of the fitting heights for each lens. This ensures that the optical centers of the lenses are correctly aligned with the wearer's line of sight, providing optimal visual comfort and clarity.

Adjusting for separate heights helps in managing issues like diplopia or discomfort that can arise from misaligned lenses. It is essential to take into account how each eye's position can influence the effectiveness of the prescription, particularly in multifocal lenses where precise alignment is crucial for an accurate visual experience.

Other situations mentioned may not require separate heights to the same extent. For example, preferring bifocal lenses does not inherently necessitate different height measurements unless eye positioning differences exist. Similarly, frame size and cosmetic adjustments pertain more to aesthetics or fitting comfort and may not directly impact the need for separate height discussions unless they are accompanied by eye positioning discrepancies.