Consider Progressives... Again
On an annual basis, I write more than a thousand prescriptions for glasses. Of those prescriptions, over sixty percent are for bifocal or progressive (multi-focal) lenses.
What are progressive lenses and why do people love them or love to hate them?
First we must appreciate how far technology has advanced since the first bifocal glasses were constructed by Benjamin Franklin in the late 18th century. Those original bifocals consisted of semi-circular pieces of glass, fused together to produce an upper distance correction and a lower magnification segment for reading. Similar principles are used in the design of modern segmented bifocals and trifocals. However, advances in lens manufacturing have resulted in bifocal lenses that bear little resemblance to that first set created centuries ago.
Unfortunately, modern segmented lenses still have a line where the two different lens powers adjoin. Some patients complain that the line is distracting. Most, however, feel that the lined bifocal indicates that they are "over the hill" and desire to eliminate it for purely cosmetic reasons. There were early attempts to eliminate the line by grinding and polishing it away. This resulted in the blended bifocal. This style of lens is still worn by some people. However, the blend results in a region of severe optical blur, which can be very annoying.
The creators of the progressive or multi-focal lens sought to design a lens that not only had no visible line, but could also provide the patient with a multiple range of focusing distances. Thus the lens would not only provide clear images at near, intermediate and far ranges, but would also allow the wearer to focus on an infinite range of in-between distances. This sounded wonderful. However, there was a price to pay for the luxury of such a broad range of focus. That price was distortion of the peripheral vision.
The older progressive lenses were plagued with terrible peripheral image distortion. In addition, the patient had to move their head to read, since the area of undistorted viewing was very small. Fortunately, recent technology has tremendously reduced the peripheral distortion and the optical region of the newer lenses is wider and more comfortable.
Progressive lenses are more difficult lenses to fit. The majority of patients who have failed progressive lenses have failed because the lenses were either fit improperly, ground incorrectly or adjusted improperly when dispensed.
