Precision is of the essence when it comes to eyeglass lenses: numerous measuring parameters and points are the key to the performance of modern, personalized eyeglass lenses.

Did You Know…

…that the Production of a Modern Eyeglass Lens Also Takes Your Nose Into Account?


High-quality eyeglass lenses are anything but mass-produced goods. They are individually designed and produced for each wearer on the basis of thousands of measuring parameters. Of course, the first thing that comes to mind is the correction of the vision defects in both eyes. However, in a worst case scenario, the pair of glasses produced may be of little use to the wearer. And the nose may well be the culprit.

Modern measuring techniques now enable opticians to capture all kinds of vision data with great precision. And state-of-the-art computer systems are so advanced that it is possible to design a customized eyeglass lens to meet the individual wearer’s particular vision requirements shortly after receiving the order from the optician. This has dramatically improved the performance of high-quality eyeglass lenses in the past 10 to 15 years. Naturally, the measured value of the vision defect plays an important role. Traditionally, it has been determined in a process known as subjective refraction (“Can you see better with this – or with this?”) for each eye. For corrective glasses to work well, however, this information has to be supplemented by data on stereoscopic vision, which is obtained by a further test method. Only when the special requirements of seeing with both eyes (binocular vision) have been properly taken into account will wearers feel comfortable using their new glasses.

The shape of the wearer’s face is also included in the calculations: How far are the pupils from the root of the nose, and are they at the same height? So far, all of these values are part of what could be called the “classic” program. However, individually designed eyeglass lenses incorporate a whole host of other parameters as well. For instance, video measuring systems can determine the position of the eyeglasses in front of the face – something that also largely depends on the nose – with a high degree of precision and in three dimensions. Conditions such as the distance of the eyeglass lens from the eye and the angle of inclination of the lens relative to an imaginary vertical axis in front of the face are of major importance as well. Even the rotation of the eyeball when shifting the line of vision is factored into today’s eyeglass lens design. All of these are critical factors influencing the optical effectiveness of the lens. Ultimately, it was the development of new measuring techniques that opened up the door to customized eyeglass lenses.

A lot has changed when it comes to perfecting eyeglass lenses that have different strengths for seeing up close and far away, i.e. the progressive lenses. It is particularly the understanding of the complex interaction of both eyes in tandem that is essential, for this is where the visual conditions resulting from different corrective strengths for seeing near, far, and in-between have to be taken into account. Today, individualized progressive lenses can be perfectly adapted to match how the wearer makes primary use of them. Depending on whether they are used outdoors or for driving, reading, or a hobby requiring meticulous attention to detail, modern, high-tech progressive lenses are designed and produced to precisely fit the particular requirements concerned. Last but not least, the wearer can freely choose among many different lens “extras”: tints, scratch resistance, dirt- and water-repellent coatings offer further personalization options.

 

21 August 2012

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