Progressive lenses, also called no-line or invisible bifocals, are the most popular type of bifocal lenses, according to the June 2009 issue of "Eye Care Professional Magazine." Cosmetically, the lenses look nice, and progressive lenses offer a more natural vision than lined bifocals. It is helpful for bifocal wearers to understand the features of different types of progressive lens styles when choosing new lenses.
Material
The first choice to make when selecting new lenses is the type of material. Progressive lenses are available in a plastic, glass or polycarbonate lens.
Glass is the heaviest of the three materials. It is also the least popular because of the weight and the limit the material puts on frame selection. Plastic progressive lenses are lighter than glass and are the most common material used today. Polycarbonate is the lightest and thinnest material. The Cleveland Clinic notes that lenses made from polycarbonate are the most impact resistant.
Short Corridor
The corridor is the vertical, hourglass-shaped area of the progressive lens that the eye follows to move from the distance prescription, through the intermediate section of the lens, to the reading prescription.
Short, or hard, corridors are most successfully used by people who need glasses with the biggest part of their viewing area in the distance and up close. The intermediate--the middle range of the lens--is used for such things as seeing a computer screen or reading a newspaper and will not have as much of a viewing area through a short corridor.
Progressive lenses with a short corridor work best for smaller frames, according to the All About Vision website.
Wide Corridor
Wide, or soft, corridors have a broader intermediate range of vision. This type of progressive lens works well in a larger frame. According to Opticianworks.com, the intermediate and reading portion of progressive lenses typically make up at least half the frame. For someone who frequently uses intermediate vision, or arm's length vision, a bigger frame and wide corridor is a good choice.
Wide corridors are recommended for people over 50 or who have had trouble getting used to a short corridor progressive lens.
Custom-Made Progressive Lenses
The newest technology in progressive lenses is high-end custom lenses. These lenses are made by computer technology that designs lenses based on multiple factors in a person's prescription and how the lenses will be used.
The March 2008 continuing education section of the magazine "20/20" explains that the new generation of optical machines are being used to enhance certain lens designs that make progressive lenses even better.
Eye care professionals trained in fitting progressive lenses will recommend the best type of lenses for individual prescriptions.
References
- Eye Care Professional Magazine: Don't Hand Me a Line! Getting to Know Progressive Addition Lenses
- Cleveland Clinic: Eyeglasses
- All About Vision: Progressive Lenses Replace Bifocals for Age-Defying Appearance
- Opticianworks.com: Module 7: Taking Measurements
- 20/20: Reducing Progressive Lens Choices to a Manageable Toolbox
