| 摘要 |
The invention relates to a multifocal ophthalmic lens, comprising an aspherical surface with a mean sphere and a cylinder at every point thereof, characterized by the equation:where L is equal to the ratio (Smax-Smin)/gradSmax, the ratio of the difference between the maximum and minimum values of the mean sphere in a region of a 40 mm diameter circle centered on the geometric center of the lens, this region being limited by vertical straight lines at 1 mm from this center on the temporal side and at 4 mm from this center on the nasal side, on the one hand, to the maximum value of the gradient of the mean sphere in this same region, on the other hand, andwhere R is equal to the ratio Cmax/(Smax-Smin), the ratio of the maximum cylinder value inside said circle to the difference between the maximum and minimum values of the mean sphere in said region.The invention provides a progressive lens with a small progression length, and a near vision region which is high on the lens. It is suitable for frames of small size, and is less tiring in extended use.
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