What is the reference point for measuring multifocal lenses?

The reference point for measuring multifocal lenses is indeed the lower edge of the lens. This is because the lower segment of the lens, or the addition segment, is where the near vision correction is located in bifocal or progressive lenses. Understanding this measurement is crucial for ensuring that the wearer’s eyes align properly with the optical zones of the lenses, allowing for optimal vision at different distances.

The position of the lower edge is intended to ensure that when the wearer looks down through the lens, especially for reading or close work, their line of sight aligns correctly with the area designed for near vision. This positioning helps avoid issues such as misalignment and contributes to comfort during wear, as well as providing clear vision for tasks like reading.

In the context of multifocal lenses, accuracy in determining the reference point is essential for fitting the lenses to the user appropriately. This impacts not only the visual performance but also the overall satisfaction of the wearer.