Line Free Bifocals For Baby Boomers Join The Digital Age
Boomers past the age of forty know what its like to have arms that suddenly are too short for reading. The lens inside the eye grown throughout your life and as it becomes larger and more rigid the focusing muscle become inadequate for clearing up near vision. That happens around the age of 40 in the United States, earlier in some countries like India. The first response is to push reading material a little farther away so less focusing is needed. Unfortunately, our arms have a limited length and sooner or later you have to make an appointment with the optometrist for that dreaded bifocal lens visit. But today we have the line free bifocal progressive lenses so only your eye doctor knows! The first successful line free lenses were the original Varilux eyeglass lenses and optometrists had to attend a training session and receive certification to dispense this new lens. If the truth be told, mostly eye doctors needed to be trained on convincing eye patients to actually wear the early forms of line free lenses since they had so much distortion of vision to the side and very narrow channels of intermediate sight. That was over 30 years ago and many generations of improvements have been made. The new Varilux lenses and their competitors such as the Autograph lens are vastly improved. Close to 98% of eyecare patients readily adapt to the line free prescription lenses that have been available the last 5-10 years-But things are taking a quantum leap as lens technology is going digital.
These are not Your Fathers Bifocals!
Traditionally, line-free progressive lenses have been manufactured on rounded metal tools referred to as laps. The manufacturer places the multifocal additive power component of the lens on the front surface in a molding process then then optical laboratory uses the tools to grind your distance prescription on the back side. Several different steps are required to polish and finish the lens. Today, optical lens suppliers are moving to a technology usually referred to as freeform. Freeform technology allows a lens to be ground by altering discrete areas of the lens instead of having to grind the whole surface with one large tool. A diamond tool is used to cut curves on the back side of the lens in points that have been digitized and fed to the cutting machine with proprietary software.The equipment is referred to as computed numerically controlled (CNC) machine tools and they allow cutting the lens in three different axes so any complex multi-curvature lens surface desired can be manufactured. The accuracy greatly exceeds traditional lens methods. In the past lenses were ground to .12 diopters, the unti of lens strength. Today they can be ground to .01diopters and each point can be ground to .1 microns (about a millionth of a meter! It actually is much higher than your optometrist can test for at this time.
Progressive Addition Lenses That Make Your Vision Better
Currently, this precise level of accuracy in manufacturing PALS (line free bifocals) is utilized by your optometrist to make vast improvements in your eyeglass prescription lenses. The frame size and shape, the distance to your eyes, and the angle of tilt of the eyewear can all be compensated for. Freefrom lenses now have atoric designs on he back surface of the lens. Since Freeform eyeglass progressive lenses are made in an aspheric design, but unlike previous generations of lenses, the aspheric component is ground on the back of the lens instead of being molded on the front. This allows the lens to flatten out towards the edges and provides a thinner, lighter, more cosmetically appealing lens. Because the asphericity ison the back it can be custom ground and correct for optical errors created by astigmatism, allowing every lens to be individually customized. Also, the progressive additive power for reading can also be ground on the back surface of the lens, creating moderate improvements in the peripheral vision. SOme new designs are splitting the near part on he front and back which increases the optical design.
Made to Order Custom Eyeglass Lenses of the Future
Progessive addition lenses have come a long way. No longer are we in the era of lined bifocal lenses, most people will not accept the performance limitations they impose. Linefree lenses will continue to improve as our capacities to test eyesight also improve. The future looks clearer every day!