Reading glasses frame can be made of various materials such as metal, plastic and alloy. Some people may do not know the fact that reading glasses frame has special requirement in its height, especially the bifocal reading glasses frame. Proper height will provide the most comfortable feeling when people wearing bifocal reading glasses. This article focuses on the height requirement and measurement of bifocal reading glasses frame.
Since the lens of bifocal reading glasses comes in two types: lens with a middle line and that without a line. The latter is also called progressive lens. As a result, the height measurement of reading glasses frame should be conducted in two ways in accordance with the lens sort. You can simply think that the lens type decides the height of reading glasses frame.
Lined bifocal height of reading glasses frame is an optical term, which describes the vertical distance from the top of the bifocal area to the bottom of the frame. Since glasses frames may fit on the different faces in various ways, the height of reading glasses frame can be calculated in another way: fitting height. This height is measured from the bottom of the frame to the lower eyelid margin.
For reading glasses frame equipped with progressive lens, the term is bifocal height. This value of reading glasses frame is measured in a single way: from the center of the pupil to the bottom of the frame. Your measurement should start at the black dot of your pupil.
The height of reading glasses frame is essential for accuracy and safety. When you make an order online, this height is required. The minimum height of the lens rim should be 32mm so that the frame can accommodate both the near and distance lenses.