Until Progressive Add Lenses (PAL) showed up multifocal lenses were a choice of Bifocal and Trifocal lenses. Bifocal lenses had only to distinct power ranges: One for seeing far and the other for seeing up close. Trifocals lenses gave us three areas and added the intermediate range focusing capability. Neither of these, though, gave us the smoother transitions between focusing on near and far objects. Bifocal wearers would often be seen bobbing their head up or down, or turning their head to bring things into focus. And many objects just couldn’t be properly focused with the fixed optical distance built into the lens segments. The hard, visible lines in the Bifocal and Trifocal lenses provided no way to avoid the abrupt jump in the focus of the object being viewed. There is no way to solve the fixed limitation of the depth of field in Bifocal and Trifocal lenses.
Bifocal lenses can put the wearer at greater risk of CVS (computer vision syndrome) that occurs when the user has to constantly tilt their heads back to see through the near distance lens segment at the bottom of the Bifocal lens. Wearers attempt to see objects at this “intermediate” range more clearly by making these adjustments and find themselves often in unnatural posture for hours at a time and this leads to muscle, neck and eye strain along with the other symptoms associated with CVS. clearly, bifocal wearers must bob their heads up and down, alternately looking through the top and then the bottom of their bifocals, to determine which part of the lens works better.
Since Progressive lenses more closely mimic natural vision wearers report more comfort and satisfaction with their eyeglasses. Progressive lenses are true multifocal lenses that provide smooth and seamless progression between lens powers that provide greater confidence to the wearer who has entered presbyopia. With clear vision across the room, up close and all distances in between, Progressive lenses are the modern answer to an age old problem.
Today advances in Progressive lens design has taken us into the digital age. So-called “high definition” progressive lenses are a great advance that is beginning to make the old cast lens styles less attractive as the software and equipment that creates digital progressive lenses improves. Computers today can use CNC (computer numerical control) lathe technology to literally sculpt the eyeglass lens to conform to the precise corrective requirements of the eye and return a much more tailored lens than old designs could hope to provide. There is nothing wrong with the older Progressive lens manufacturing processes but with the advance of computers and lathing equipment in the optical industry the future is bright and promising for the digital era of progressive lenses. At EyeglassUniverse.com we are able to extend the prescriptive range we can solve for our patients using the digital Progressive lens and digital lens versions are available across the range of lenses we offer including single vision lens products, task specific lenses, and soon, we’re sure, other types as well.