High-quality eyeglass lenses are anything but mass-produced. They are individually designed and produced for each and every wearer on the basis of thousands of measuring parameters. Needless to say, the first and foremost goal is to correct the wearer’s visual defect that has been measured by the eye care professional. If the worst comes to the worst, however, a pair of glasses may result that do not really meet the wearer’s vision requirements. And the nose may well be the culprit.
Modern techniques now enable eye care professionals to measure many different vision parameters with the utmost precision. And leading-edge computers are so advanced these days that, after receipt of the order, this data is turned in real time into a tailor-made lens sharply focused on each wearer's personal needs. This has all led to a decisive improvement in the performance of high-quality eyeglass in the past 10 to 15 years. The visual defect measured by the eye care professional plays a central role here, of course. Traditionally, it is determined in a process known as subjective refraction (“Is this lens better – or maybe this one?”) for each eye. If the final glasses are to optimally correct the wearer’s vision, the measured visual defect must be supplemented with data on three-dimensional vision, which is obtained using a further test method. Only if the special needs of binocular vision are considered will the wearer feel totally at home with his or her new glasses.
The shape of the wearer’s face is also taken into account: how far are the pupils away from the bridge of the nose, and are they at the same height? These are more or less the “classical” values associated with the lens production process. Individualized lenses go a lot further by incorporating a large number of other parameters. Video measuring systems can measure the position of the eyeglasses in front of the face, also largely determined by the nose, with extreme precision and in three dimensions. Here, aspects like the distance of the lens from the eye and the angle of inclination of the lens relative to an imaginary perpendicular axis are also of major importance. Even the rotation of the eyeball when the line of vision is changed is now factored into the lens design. This all influences the optical power of the lens. In other words, it was the development of new measuring techniques that ultimately opened the door to tailor-made, individualized eyeglass lenses.
A lot has happened in the optimization of eyeglass lenses that display a smooth transition of power from the distance to the near zone – progressive lenses. Here, an in-depth understanding of the complex interaction of the two eyes is crucial as the visual conditions resulting from different corrective powers in the near, intermediate and distance zones must be taken into account. Today, individualized progressive lenses can be perfectly matched to the wearer’s main field of activity. Whether they are used outdoors, for driving, reading or for a hobby requiring meticulous attention to detail, modern, high-tech progressive lenses are designed and produced to precisely meet the intended purpose. Last but not least, there are many different options to further enhance the lens: tints, scratch resistance and dirt- and water-repellent coatings offer further optimization possibilities.
August 22, 2012