Trifocal lenses are similar to bifocals, except that the two focal areas are separated by a third middle area with intermediate focus correction, used forinter mediate vision, e.g. computer distance. This lens type has two segmentlines, dividing the three different correcting segments.
Trifocals are fitted a bit higher, with the top line of the intermediate areaplaced even with the pupil. A trifocal wearer focuses through the intermediate prescription area of the lens when looking at something between 18 and 24inches away.
The eyes gravitate straight ahead, or up and over the multifocal segments, when gazing at something in the distance. An E-Dtri focal has 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 theway across the width of the lens in the Executive bifocal style, and a D half-moon segment containing the near correction that resides within the lowerhalf of the lens.
The E-D trifocal is for someone who must see at the inter mediate distance in a wide field of vision and who also must see clearly both close-up and in the distance. A television production person, for example,who must keep an eye on several TV monitors spread out in front and to the sideswhile being able to read notes from a clipboard and recognize someone acrossthe room, is a good candidate for this lens.
Example of Trifocal Lenses
"Height x Width"
7x28 – 7mm x 28mm
7x35 – 7mm x 35mm
8x35 – 8mm x 35mm
9x35 – 9mm x 35mm
10x28 – 10mm x 28mm
10x35 – 10mm x 35mm
DD FT 28 –Double D Flat Top 28mm
DD FT 35 – Double D Flat Top 35mm
Executive Trifocals