Column: All no-line bifocals are the same, right?


Commentary by Jeremy Ciano

When it comes to seeing clearly at all distances, there is a huge difference in no-line bifocals (also known as no-line trifocals or progressive lenses) designs and manufacturers.

Let’s start with the basics. If you look through a keyhole, the closer you get, the more of a room you can see. As you move back, you see less and less. This is called field of view. In digitally processed, progressive lenses, the prescription can be etched onto the back surface of the lens (closer to your eye) to give you a wider field of view. Older technologies that are hand ground onto the front surface of the lenses give a much narrower and restricted peripheral field view as well as “swim and sway” distortion and adaptation issues.

Another alarming difference between digital progressive lenses is in the precision and accuracy of the prescription. Manually ground lenses at your local one-hour retailer, or your typical insurance-grade/mass produced lenses, are measured in 0.25 of a diopter. Digitally fabricated lenses are accurate to 0.01 diopter. That is 25 times more accurate! That precision and accuracy is analogous to the difference between watching your favorite movie on VHS or Blu-Ray, using a 1.0 megapixel camera versus a 12 megapixel iPhone, or listening to music on an LP versus a CD.

When discussing these differences, I always try to make the analogy to my patients the difference between a donut tire and a 50,000-mile, all-weather tire. Technically speaking, they are both tires, but given the option of driving on the highway at 55 mph in the rain, do you honestly think they perform equally? The same is true with no-line progressive lenses. They don’t all perform the same.

So, the next time you are making the investment in your vision for the next few years, make sure you understand all of the huge technological differences.