Standard and modified occupational multifocal lenses

Monday, January 18th, 2010 at 2:46 pm Post in Eyeglasses

Most people with presbyopia get satisfying vision correction from conventional bifocal or trifocal lenses. But for those spending all day long in a job or hobby that requires only near vision or distance vision, special occupational bifocals or trifocals are needed. These special occupational multifocal lenses have unusual placement of near, intermediate and far vision zones in the lenses, meeting different, specific needs.

In most cases, near vision zone is placed at the bottom of a multifocal lens. But some professionals such as auto mechanics, librarians and mail clerks require both overhead near vision and downward near vision. Double-D lenses are the perfect choice for this kind of tasks. A double-D lens has a D-shaped bifocal segment at the bottom and another upside-down D-segment at the top. Double-round lenses are similar to double-D ones.

While double-D lenses favor near zones, another type of occupational lenses named E-D lenses emphasize on intermediate zones. An E-D trifocal lens has a top half part for distance vision and a bottom half part for intermediate vision. The near vision segment only occupies a small D-shape area of the bottom part. With a wide area of intermediate zone, this type of trifocal lenses is suitable for television production workers.

Occupational multifocal lenses can be achieved by simply positioning common multifocal lenses in unusual ways. Ordinary trifocal lenses are properly fitted by placing the top line to be just below the pupil. By placing trifocal lenses higher, the wearer is needless to look down or tilting back the head to get near vision. This type of occupational lenses fit a pharmacist but is not suitable for a driver.

A golf-specific occupational lens can be achieved by placing a round-top bifocal lens low and in the outside corner of one lens only. In this way, the near vision zone is put aside but it is still enough for the golfer to read a scoreboard. What’s beneficial, distance vision can be significantly expanded, which is helpful for shot-making and lining up a putt.