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sports & performance
Many frame suppliers entrust Lenstec to Glaze their 8 Base prescription eyewear Oakley, Klein, Nike, Police, Rayban, Performer lifestyle and many others also many of the smaller high class manufacturers are producing frames with deep curves of 6D to 8D .
As we all know it becomes increasingly difficult to come up with a new fashion idea, something which is genuinely different and there is no doubt that stylish frames in wrap around format are innovative and attractive for prescription wearers.
Up till now the two main technical problems associated with glazing these frames in a cosmetically and optically satisfactory way have made it virtually a no go area. However recent advances in both these separate areas have combined to defeat the gremlins.
The Panoramic tilt
( wrap angle of the frame)
Creates a ‘Prescription error
This acts as a constraint to the
optical optimization process
during the lens design
The actual optical power
required is different from
the prescription |
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A new glazing technique available from Lenstec Optical Laboratories capable of following accurately the edge of these steeply curved lenses and creating a sophisticated and individually tailored bevel with a unique profile has at last dealt properly with the cosmetics of the glazing.
The difficulties of creating this edge should not be underestimated and the process still requires highly skilled technicians capable of a detailed pre check process and an understanding of the edging process.
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A gauge of this is the need for example to place the bevel on polarised lenses away from the laminate and keep it there for the full rotation of the deep base edging run, requiring not millimetre perfect operation but tenth of a millimetre accuracy.
The second problem encountered with early base 8 glazing was that most wearers experienced significant spatial distortion with the end product. This was highly limiting especially for sportsmen like golfers, cyclists, etc. who are the most likely wearers of the sunglass version of this product.
This was a little baffling at first until it was realised what turning a lens through 20 or 25 degrees of rotation in front of the eye does to the resultant prescription. Now Performer Lifestyle Lenses, a German company have developed software to compensate for this twist around the vertical axis of the lens which can induce changes in the sphere, cylinder, axis and even prism power, so that the delivered prescription in the wrap frame produces the exact equivalent of the trial frame prescription.
This new lens range from Performer has eliminated the high number of grief cases experienced with current unmodified wrap lenses, normal curved 8 base lenses are just not optically suitable to the wearer.
This, of course, requires an accurate measurement of the frontal angle of each frame used, unless one of Performer’s own range of wrap frames are used when they have predetermined that angle.
So whether it is an Oakley, Nike or Performer frame these can now be glazed with utter confidence that no matter how demanding the final user’s vision requirements may be, the result will be successful distortion free vision. And this goes for high index, polarised, mirror coated, and even varifocals.
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