US 6,318,859 B1 · Set of progressive multifocal ophthalmic lenses

Abstract

The invention concerns a set of progressive multifocal opthalmic lenses, each having a first progressive multifocal surface and a second surface preferably spherical. It proposes to define the set of lenses with regard to the optical characteristics of the lenses, and particularly wearer power and oblique astigmatism, in worn conditions. For this purpose, the invention defines an ergorama associating with each sight direction in worn conditions a target object point, and a given power. This ergorama supplies a power target for a definition by optimisation of the lenses, and is used in a radii plotting programme for calculating the optical characteristics during optimisation. The set of lenses has substantially identical optical performances for a given addition, whatever the power of the far vision reference point.

Claims20

Dependent claims

A set of progressive multifocal ophthalmic lenses determined by means of ergoramas that associate to each direction of glance a nearness in the object space and a power, for a given ametropia and a given addition of a standard person wearing the lens,

in which, for a lens under the conditions in which it is worn, a wearer power is defined in a direction of glance and for an object point, as the sum of the the degree of nearness of an object and the degree of nearness of the image of said object point,
in which each one of said lenses has:
a first and a second surface, said first surface being a progressive multifocal surface;
a far vision region, a near vision region and a main meridian of progression passing through said two regions, said far vision region, near vision region and meridian being sets of directions of glance under the wearing conditions;
a power addition A equal to a variation in wearer power for the point towards which the glance is directed in the ergorama, between a reference direction of glance in the far vision region and a reference direction of glance in the near vision region;
and in which variations in wearer power along said meridian, for the said point towards which the glance is directed in the ergorama are substantially identical for each one of the lenses of a set having the same power addition.

3 more elements

A method for determining an ergorama for a set of progressive multifocal ophthalmic lenses, said ergorama associating, for each lens and for each direction of glance, a nearness in the object space and a power, for a given ametropia and a given addition of a standard person wearing the lens, the method comprising the steps of

defining standard characteristics of a wearer, and notably ametropia and power addition;
defining an environment in the form of a set of object points to be looked at, for the standard wearer;
calculating the direction of glance for a reference object point for near vision, using a thin lens approximation, for a power calculated from said ametropia and said power addition;
calculating accommodation from the direction of glance for said reference object point for near vision and from the distance between pupils;
determining the wearer's Donders curve, from accommodation and convergence for said reference object point for near vision;
determining a direction of glance for other object points in an environment, using an iterative process, for a thin lens approximation, based on said Donders curve.

3 more elements

Dependencies are inferred from the claim text.

Set of progressive multifocal ophthalmic lenses

Life of this patent

Set of progressive multifocal ophthalmic lenses

Life of this patent

Abstract

Claims20