| 摘要 |
The invention concerns a progressive multifocal ophthalmic lens, comprising an aspherical surface, with equal addition value to the mean sphere difference between a reference point of the near-vision region and a reference point of the far-vision region. It has a progression length less than 12 mm, the progression length being equal to the vertical distance between a mounting cross and the point of the meridian where the mean sphere value is higher by 85 % of the addition value than the sphere value at the reference point for far-vision. To provide the lens with good vision characteristics, not only about the meridian, but also in the extrafoveal vision regions, the ratio between the product of the cylinder by gradient norm of the sphere and the square of the addition value is less than 0.08 mm-1 at any point of a disc with a diameter of 40 mm centred on the lens centre. Additionally, the cylinder in the part of the disc located above the mounting cross in less th an 0.5 times the addition value. Said characteristics ensure optical performanc es of the lens, despite the low value of the progression length.
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