Occupational Bifocals and Trifocals

An occupational lens is a type of multifocal that is generally suited for performing a particular job or hobby and is not meant for everyday wear.

An example of an occupational bifocal is a Double-D, which consists of a half-moon-shaped flat-top bifocal at the bottom of the lens and an upside-down flat-top at the top of the lens. The rest of the lens area consists of distance correction.

In the Double-D, there are two segments for near vision (here, green and blue). Graphic courtesy of Joe Bruneni, Vision Consultants, Inc.

People in occupations such as a car mechanic, who would need to be able to see well at the near point both looking down to read as well as looking up above his head to work on the undercarriage of a car on a lift, would benefit from a lens such as the Double-D. Double-round segs are also occupational lenses that can be used for the same purposes as the Double-D.

An E-D trifocal consists of a distance correction along the top half of the lens, separated from the intermediate correction in the bottom half by a line that goes all the way across the width of the lens (called Executive style), and a D half-moon segment containing the near correction that resides within the lower half of the lens.

The E-D trifocal is suitable for someone who needs to see at the intermediate distance in a wide field of vision and to see clearly both close up and in the distance. A television production person, for example, who must keep an eye on several TV monitors that are spread out in front and to the sides while being able to read notes from a clipboard and recognize someone across the room, would be a good candidate for this lens.

Sometimes a common multifocal can become an occupational lens simply by changing the way that it is placed in the eyeglass frame. Instead of placing a long, narrow rectangular ribbon seg just at the bottom eyelid, where bifocals are normally situated, for example, the ribbon seg can be moved to eye level. The wearer would then look through the near vision correction rather than through the distance correction when standing or sitting in a normal position.

While this placement of the bifocal wouldn't be ideal for everyday tasks such as driving, it would be good for a pharmacist who must read the small print on labels right in front of her all day long.

Flat-top bifocals often are placed extremely low and in the inside corner of one lens of a pair of golf glasses: just enough near vision correction is placed in the eyeglasses to allow the golfer to read and write on the scorecard without compromising the vision necessary to hit the sweet spot on the golf ball.

Most segmented multifocals are available in all lens materials, including glass, plastic, high-index and polycarbonate in addition to photochromic glass, plastic and high-index materials.