A flat top 28 bifocal lens is offers correction for both near and far distances. It is a multifocal lens commonly prescribed for those suffering from both presbyopia and hypermetropia, a condition whereby, with age, the eye exhibits a progressively diminished ability to focus on near and far objects. The flat top lens includes a segment at the lower half of the lens with a prescription for reading (near distance). The width of the flat top 28 bifocal is 28mm wide at the top of the bifocal and looks like the Letter D turned 90 degrees.
Because the flat top bifocal is one of the easiest multifocal lenses to adapt to, it is one of the most popular bifocal lenses in the world. It's distinct "jump" from distance to near vision gives wearers two well-demarcated areas of their glasses to use, depending upon the task at hand. The line is obvious because the change in powers is immediate with the advantage being it gives you the widest reading area without having to look too far down the lens. It is also easy to teach someone how to utilize the bifocal in that you simply use the top for distance and the bottom for reading.
Some presbyopes choose progressive multifocal lenses, which gradually change powers from the top portion to the bottom of the lens, without lines to separate them. However, conventional bifocals offer some advantage over progressive lenses, such as providing wider lenses for computer work and reading compared to progressive lenses. Special purpose bifocals are also available for computer work and other tasks requiring powerful near and intermediate vision.
| || |
While bifocals work great for tasks like driving and reading, they are limited in their ability to provide clear vision at points in between, such as the distance to a computer monitor.
Compared with progressive lens, the advantages of bifocals is that they are dependable and typically less expensive than progressive lenses.