Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1995-06-05
1999-11-30
Epps, Georgia
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
351176, G02C 706
Patent
active
059929987
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an ophthalmic lens having a progressive optic power, the line being provided with at least one surface having a surface power which changes in such a manner that, starting from at least one region, in which the optic power of the ophthalmic lens is practically constant, the optic power of the ophthalmic lens changes along at least one line (hereinafter referred to as the main line) which may lie in a plane or be sinuous and on which there is a prescribed astigmatism which is not identical with zero diopter.
STATE OF THE ART
Ophthalmic lenses having a progressive effect according to the introductory part of claim 1 are, by way of illustration, known from DE 30 16 935 C2, DE-PS 1 145 820 or GB-PS 775 007.
In the case of the ophthalmic lenses having a progressive effect known from the patent literature and/or available on the market, the inevitable surface astigmatism present on a surface having a varying surface refractive power is rather regarded as an accompanying factor to be taken into account, the amount of which should not, at least on the main meridian respectively main line, exceed a physiologically disturbing value; with regard to this reference is made to the previously mentioned DE 30 16 935 C2 or EP 0 027 339 A2. It has even been frequently proposed to form the main meridian as the umbilical line, i.e., as the line in which the surface astigmatism is zero; with regard to this reference is made, by way of example, to DE-AS 20 44 639 or DE-PS 28 14 936. The axial position of the astigmatism finds no consideration in these printed publications.
Apparently, it is accepted that the axial position of the surface astigmatism is set according to surface theoretical considerations and not according to physiological ones: as the overall astigmatism is yielded by the geometric addition of the surface astigmatism and the oblique astigmatism, the axial position of the overall astigmatism varies along the main meridian respectively the main line (which may follow approximately the main line of vision) in such a manner that a clear-vision-preventing variation of the axial position of the overall astigmatism along the main meridian respectively along the main line is yielded.
If an ophthalmic lens having a toric respectively astigmatic effect suited for corrective purposes can now be realized with the state of the art progressive surfaces, the astigmatic effect required for correction is achieved solely due to the design of the second surface: in this event, the second surface is designed as a toric respectively an atoric surface (cf., e.g., DE 30 16 936 C2). The term "atoric" means a surface with an astigmatic power, in which at least one main section is not spherical, namely the shape of one main section departs from the shape of a circle.
Only DE-PS 1 145 820 mentioned in the introduction describes a surface the surface astigmatism of which has a constant amount over the entire surface yielding, taking the second surface into consideration, an ophthalmic lens having a specific astigmatism which can also serve corrective purposes. In this state of the art ophthalmic lens, the axial position of the surface astigmatism of progressive surfaces is constant along the plane main meridian, noteably 0.degree. respectively 90.degree..
An axial position deviating therefrom has therefore to be realized by means of the second surface, nonetheless yielding, in the event of use of a toric second surface, a physiological, possibly, disturbing variation of the overall astigmatism while taking into consideration oblique astigmatism.
DESCRIPTION OF THE INVENTION
The present invention is based on the fundamental concept of improving an ophthalmic lens with a progressive effect having at least one surface with a surface power which changes in such a manner that, starting from at least one region in which the effect or the optic power of the ophthalmic lens is at least approximately constant, the optic power of the ophthalmic lens changes along a line (hereinafter referred to
REFERENCES:
patent: 4613217 (1986-09-01), Fuerter et al.
patent: 4786160 (1988-11-01), Furter
patent: 4854689 (1989-08-01), Dufour et al.
patent: 5488442 (1996-01-01), Harsigny et al.
Altheimer Helmut
Haimerl Walter
Pfeiffer Herbert
Epps Georgia
Optische Werke G. Rodenstock
Schwartz Jordan M.
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