Types of Prescription lenses
- Single vision lenses
- Bifocal lenses
- Multifocal lenses
- Extended Focus occupational lenses
- Polarised prescription sunglass lenses
Single vision lenses
These are the most common type of prescription lenses. They may be used in reading glasses, driving glasses or computer glasses. If you are under forty, this is most likely the type of lens that you would require to correct your vision.
First designed by Benjamin Franklin, these lenses have two different prescriptions separated by a line in the lens. The most common use for these is to have your distance prescription in the top of the lens and your reading prescription in the bottom segment. On most bifocals, you can clearly see the line separating the two prescriptions.
These lenses have multiple prescriptions of different focus incorporated into a single lens. There is no visible line separating the different focal areas. They are also called graduated or progressive lenses. The lens wearers distance prescription is set at their normal viewing position, this blends into an intermediate zone below this, and the reading area is at the bottom of the lens.
Early multifocal lenses were difficult to get used to due to lots of visual distortion at the lens edge, and only a small area of clear vision. Newer designs have sort to reduce the peripheral distortion and increase the areas of clear vision within the lens.
At J & J Optical we recommend the use of FreeForm designed multifocal lenses. FreeForm is a computer designed and digital surfacing process and is the latest technology in multifocal lens manufacturing. Similar to Laser eye Surgery, lenses made from FreeForm digital surfacing are manufactured using Wavefront Physics. This matches the lens to a person's prescription and the shape of the frame they have chosen, providing a clearer image and a wider field of view.
Benefits of Free Form multifocal lenses
- Wider areas of clear vision
- Provide better control of image distortion
- Less peripheral distortion
- Lenses are specifically manufactured to match the patient's prescription and the frame shape
- Easier for first time multifocal wearers to adapt
Extended Focus Occupational lenses
Extended focus lenses are designed to be used for reading and computer work. Single vision reading glasses are often set at a distance of 30 to 40cm away from the eyes. Most computer screens are positioned 50 to 60cm from the eyes. This often requires a different prescription to focus at that distance. Instead of having a pair of glasses for reading and an additional pair of glasses for the computer, there is the option of having the reading and computer prescription combined into one extended focus lens.
Extended focus lenses contain the reading prescription in the lower segment and blend into an intermediate distance prescription in the top of the lens. Most people will need to take them off to walk around.
Prescription Sunglass lenses
There are two main types of prescription sunglass lenses - tinted lenses and polarised lenses. We recommend polarised lenses for most of our patients, as they offer better glare protection and reduce light reflection from surfaces such as the water, the road, and car windscreens. Polarized sunglass lenses also provide superior glare reduction for outdoor activities such as fishing, sport, and going to the beach.
Previously, it was difficult to do prescription sunglass lenses into many of the fashion or wrap sunglass frames. New lens grinding technology allows us to put prescription lenses into these frames and reduce the peripheral distortion caused by the curve of the lens and frame.