How can it be a bifocal without a line?
About Progressive Lenses
Progressive bifocals are far more complicated than standard lined bifocals. Whereas lined bifocals are a simple dome-like magnifying area which resides on top of your prescription, progressive bifocals come to a magnifying area progressively, from the center of your vision down to a reading area at the bottom. This means that your prescription changes consistently as you look down until you get to the reading circle.
If you’re wondering how progressive lenses work, here’s the answer to your question:
- Progressive lenses are essentially bifocals without a line, though they are more complicated than that as well.
- The top part of a progressive lens is your distance prescription. As your eyes descend below the center of your vision, the prescription progressively changes to be focused closer and closer until you reach a circle at the bottom of your vision that is for reading.
- To put it visually, the progressive corridor and reading area are shaped like a mountain range on your lens, where the shortest part of the mountain is where the corridor starts on top, and there is a plateau at the top of the mountain where your reading circle is.
- The areas to the right and left of the progressive corridor and the reading area are not usable because of the nature of progressive lenses, so they will be unclear compared to the rest of the lenses. Luckily, these areas are seldom used and this is easy to get used to.
- Progressive lenses must be lined up so that the progressive corridor starts right when your eye passes the center of your vision. This means that the distance between the bottom of the lens and the center of your pupil (while looking straight ahead) must be measured in order to make progressive lenses for you. This measurement is called “segment height,” and it is different for every person, and for every frame as well.
Progressive bifocals are preferred by most people because they look better than conventional bifocals and generally are not too hard to get used to if you’ve never worn traditional bifocals before. If you’ve worn traditional lined bifocals, you may have a hard time adjusting to progressive lenses and might want to think twice before purchasing progressive lenses.
Progressive no-line bifocal lenses are a great choice for most people who are looking for everyday glasses. They are not as good of a choice for those looking for wraparound prescription glasses, as the progressive nature may be harder to adjust to in a curved lens.
If you have any questions or comments about this post or progressive lenses, don’t hesitate to leave them in the comments below! Thanks for reading, and happy shopping!