Progressive multifocal ophthalmic lens

Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks

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G02C 706

Patent

active

057084939

ABSTRACT:
A progressive multifocal ophthalmic lens is provided having an aspherical surface with a mean sphere and a cylinder at every point. The aspherical surface has a distance vision portion, with a control point for distance vision, a near vision portion with a control point for near vision, and an intermediate vision portion between the near vision portion and the distance vision portion. A power addition value A is defined as a variation in mean sphere between the control point for distance vision and the control point for near vision portion. A base B is defined as a value of mean sphere at the control point for distance vision. A width of the near vision portion varies not only as a function of the power addition value A, but also as a function of the value B of the base. The invention thereby ensures the presence of a substantially constant object field for all values of the power addition and of the base.

REFERENCES:
patent: 5000559 (1991-03-01), Takahashi et al.

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