Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
1999-08-09
2001-04-10
Epps, Georgia (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S176000
Reexamination Certificate
active
06213603
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a progressive ophthalmic lens.
2. State of the Art
Progressive ophthalmic lenses are, by way of illustration, known from DE-C-30 16 935 or WO 95/27229. Moreover, reference is explicitly made to the latter publication regarding all terms not defined in detail herein.
The known generic progressive ophthalmic lenses have one or two surfaces with continuously varying power (progressive surface). On a progressive surface, the power increases from the respective suited-for-distant-vision value BK [dpt] in the distance reference point with the coordinates x=0 mm, y=8 mm (selected within the scope of the present application) in the lower region of the distant vision part along a sinuous line to a suited-for-near-vision value BF [dpt] in the near vision reference point, which is located in the upper region of the near vision part. The value BF is higher by the amount Add [dpt] of the addition than the power BK in the lower region of the distant vision part.
The course of the sinuous line, which hereinafter is also referred to as the principal line, is selected in such a manner that it coincides at least approximately with the principal line of vision when the glance is lowered, i.e. with the point of penetration of the visual ray through the surface with continuously varying power when the glance is lowered. With ophthalmic lenses, in which only one surface, usually the front surface, of the ophthalmic lens contributes to the power variation, the eye-side surface is designed to be spherical or aspherical in the case of an astigmatic prescription, toric or atoric.
In the known progressive ophthalmic lenses of the type mentioned in the preceding, the distant vision zone is relatively large so that it grants the wearer a good general view over a wide range without any turning of the head.
However, the near vision zone is relatively narrow so that the head already has to be turned when reading a newspaper in order that several columns may be viewed. In the state of the art, particularly ophthalmic lenses which have negative power in the distant vision zone and are made of a high-refracting material, have an especially narrow near vision zone.
DESCRIPTION OF THE INVENTION
The object of the present invention is to provide a progressive ophthalmic lens, which can have negative power, in particular, in the distant vision reference point and is made of a material with a refractive index of >1.58 and which has a relatively wide near vision zone.
According to element of the present invention the surface astigmatism of at least one of the surfaces contributing to the power variation along at least one intersection of the ophthalmic lens with a horizontal plane (y=const., hereinafter referred as horizontal intersection) has a local maximum value, which is at a distance of not more than 4 mm, preferably not more than 2 mm, from the principal line, and at least one local minimum value, which does not lie on the principal line, and which is at a greater distance from the principal line than the local maximum value.
Thus, the concept of the progressive ophthalmic lens of the present invention breaks with the conventional manner of proceeding: in the known progressive lenses the surface astigmatism on the principal meridian or the principal line has a minimum value, usually even an absolute minimum value. In ophthalmic lenses in which the principal line is designed as a so-called umbilical line, i.e. as a sequence of points at which the surface astigmatism is 0 dpt, this is already yielded by Minkwitz's principle, according to which the surface astigmatism increases perpendicularly to an umbilical line with a gradient having twice the value of that of the surface power on the umbilical line,
Even for ophthalmic lenses, in which the surface astigmatism on the principal line is not 0 dpt, but a certain amount of the surface astigmatism is selectively “taken into account” in order to reduce the peripheral aberrations, the amount of the surface astigmatism on the horizontal intersections on the principal line has a minimum value, usually an absolute minimum value. With regard to this, reference is made to DE-C-30 16 935 mentioned in the preceding, in which the progressive lenses are described with a surface astigmatism on the principal line of vision, which, in order to correct the peripheral aberrations, deviates from the value of 0 dpt in the progression zone. DE-C-30 16 935 imparts, in particular, the teaching that astigmatism in the progression zone starting from a value of 0 dpt at the lower edge of the distant vision zone should attain a maximum value in the progression zone and subsequently should drop again to a value of 0 dpt in the upper region of the near vision zone.
In accordance with the present invention it has been recognized that an improved ophthalmic lens with an, in particular, wider near vision section is yielded by forfeiting this traditional concept.
A distant vision zone is provided, which is disposed in the upper part of the ophthalmic lens and in which the near vision zone(s) is (are) disposed in the lower part of the ophthalmic lens, it is especially preferred if the horizontal intersection(s) on which a local maximum value of the surface astigmatism occurs, lies in the lower part of the progression zone and/or in the upper part of the near vision region. In this way a near vision zone is yielded, which is at least 25% wider than the near vision zone in known generic progressive ophthalmic lenses. It is assumed in accordance with the usual definition, that the delimitation line of the near vision zone is the line on which the amount of the overall astigmatism, thus not the surface astigmatism, has a value of 0.5 dpt.
Within the scope of the coordinate systems selected in the present application, numerical y-values, in which a local maximum value of the surface astigmatism occurs on the principal line or in the immediate vicinity thereof for all the horizontal intersections.
The surface astigmatism in the upper part of the progression zone and in the distant vision zone has a minimum value on the principal line. This teaching contradicts that of DE-C-30 16 935.
It is explicitly pointed out that the concept of the invention for the course of the surface astigmatism along the horizontal intersections does not mean that the overall astigmatism also has a topologically similar course.
Rather, the overall astigmatism on the principal line on each horizontal intersection has at least a minimum between y=15 mm, and y=−20 mm, that can assume absolutely very small values and, in particular, the value of 0 [dpt].
Consequently the concept of the present invention means that, at least in the lower region of the progression zone and in the upper region of the near vision zone, the principal line is not an umbilical line. Therefore, it is particularly advantageous if the surface astigmatism increases approximately linearly along the principal line in the lower region of the distant vision part. Yielded is a “soft” transition from the “essentially surface astigmatism-free” distant vision zone, in which there is no or only minimal surface astigmatism on the principal line and in a large surrounding region, to the parts of the surface, in which the principal line has surface astigmatism.
The transition can occur by the gradient of the function of the surface astigmatism on the principal line being a function of the base curve and of the addition.
Furthermore, in accordance with the present invention, it has been realized that a better corrected ophthalmic lens is yielded if the gradient of the horizontal intersections on the site of the principal line as a function of y is not strictly monotonous. The correction can be further improved if the gradient of the horizontal intersections on the site of the principal line as the function of y is not only not strictly monotonous, but according is not monotonous at all.
It is, in particular, only necessar
Altheimer Helmut
Barth Rudolf
Esser Gregor
Fuess Monika
Haimerl Walter
Antonelli Terry Stout & Kraus LLP
Epps Georgia
Optische Werke G. Rodenstock
Schwartz Jordan M.
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