Many progressive lens wears have the same questions about their lenses. These questions generally are, why do I have to move my head to see different objects, why are the sides blurry and why does everything sway when I turn my head from side to side. All of these issues are caused by two factor of progressive lenses. Channel width and astigmatic aberration. Great problem solved, only what does that mean? Before we can answer this we need to know a little bit about progressive lenses.
It is widely believed that Duke Elder made the world’s first commercially available PAL (Progressive Addition Lens) in 1922 and was based on an arrangement of aspherical surfaces. These sold for a short time but were not met with a great reception. The Varilux & Carl Zeiss lenses were the first PAL of modern design. Developed by Bernard Maitenaz in 1953 and introduced by the Société des Lunetiers (which later became part of Essilor) in 1959. The breakthrough for the adaptation and the comfort of the progressive lens occurred in 1972 with the market introduction of Varilux 2. Bernard Maitenaz discovered the importance of the design periphery for the peripheral and dynamic vision. So while for Varilux the surface structure was close to the characteristics of the bifocal lens, Varilux 2 was distinguished by a totally aspheric design. Since that time very little has changed in the production of progressive lenses other than clever marketing.
To simplify how progressive lenses work we can say that the lenses starts with a certain curve that fits directly over your eye when you are looking straight ahead with you chin level. As you move down the lens that curve gets greater creating more magnification giving you focal points for your intermediate and reading distances. In order to do this properly only a small portion of the lens can be focused on to achieve the proper curve. This area is referred to as the “channel”. This channel is where the prescription is held, has an hour glass shape and is where you must look through in order to see properly. While the channel is the reason you have to move your head in order to look through the correct portion of the lens, outside of this channel lies the astigmatic aberrations which, is a distorted area in the lens that does not bend light to the proper focusing point for you to see clearly out of. These astigmatic aberrations are what cause the distortion is what makes the edges creating the blur as well as the swaying feeling when moving your head from side to side.
While there are these small issues with progressive lenses nearly all people adjust to these issues, after a short adaption period, and overall are pleased with how they look and work. The adaption period, generally, is just a handful of days with. At Schmidt’s Optical and Hearing™ Stuart FL we fabricate progressive lenses in house and can have a new pair ready for you in as little as an hour. Visit us at 2341 SE Federal HWY, Stuart, FL. 34994 and pick out a great looking pair or two.