The present invention relates to a bifocal or multifocal contact lens as per the preamble of patent claim 1.
Bifocal and multifocal contact lenses serve to correct different visual, defects. By way of example, they allow a nearsighted person, who at the same time suffers from age -dependent hyperopia, which is also referred to as presbyopia, to have visual-acuity correction over a large distance range.
Such bifocal and multifocal contact lenses usually have two or more concentric circular or annular zones with different optical corrections. This is illustrated in
In other embodiments, two correction zones with a correction for distance vision and near vision are applied onto the contact lens, with these zones being separated by a horizontal intermediate zone Z running through the center of the lens. This is illustrated in
WO 2008/002976 moreover discloses a contact lens with at least one near-vision zone and at least one distance-vision zone. The near-vision and distance-vision zones respectively have a circular or elliptical design, and lie within one another. In doing so, they contact one another tangentially at their edges.
EP 0 624 811 shows a multifocal contact lens with a segment-like near-vision-zone region and a circular distance-vision-zone region, which touches an edge of the near-vision-zone region.
EP 0 949 529 describes a toric multifocal contact lens for correcting different corneal curvatures in various optical zones. By way of example, the lens has a circular near-vision-zone region, which is arranged concentrically in a circular distance-vision-zone region.
It is an object of the invention to create a bifocal or multifocal contact lens, which ensures optimized visual acuity for nearby and at a distance, even in the case of strong corrections, more particularly in the combination of severe myopia with age-related presbyopia.
This object is achieved by a contact lens with the features of claim 1.
The bifocal or multifocal contact lens according to the invention with a geometric lens center point has a circle-like near-vision zone with a first geometric center point and a circle-like distance-vision zone with a second geometric center point. The near-vision zone and the distance-vision zone are arranged concentrically, as a result of which the first geometric center point and the second geometric center point coincide and form a common correction center. In doing so, this correction center is situated at a distance from the lens center point,
Thanks to the eccentrically applied circle-shaped and ring-shaped correction, there are no distracting intermediate zones, which can, for example, create reflections that irritate the user. The correction zones preferably merge continuously and abruptly into one another. In place of circle-shaped correction zones, it is also possible to use elliptical, oval or similar shapes. Since the individual correction zones are superposed on one another, the outer correction zones have a ring-like shape. Moreover, it is not necessary for the whole ring or the whole circle to be situated on the lens. Depending on the distance of the correction center from the center point of the contact lens, the circles or rings may only be present in sections.
Thanks to the upward displacement of the center of the correction zones relative to the center of the lens, a downward displacement of the lens, caused by eye movement, brings about an effective distance-vision zone, which is enlarged for distance vision. An upward displacement of the lens brings about an effective correction zone, which is enlarged for near vision.
Thanks to the horizontal subdivision of the correction zones, broad, integral areas are available per correction zone, which allows a continuously increasing utilization of the correction zones if the pupil size increases. As a result, the effective luminosity is additionally increased in the case of good visual acuity.
In the case of an overall negative correction, the lower half, or more or less the lower half, of the contact lens is thicker than the upper half. Hence, the lower half is heavier, as a result of which there is an automatic upward alignment of the contact lens with the center of the optical corrections.
In the case of an overall positive correction, it is advantageous to add a prism correction in order to obtain the desired rotationally secure alignment of the lens. This can easily be attached because the region of the lens adjoining the near-vision zone to the bottom is no longer relevant from an optical point of view. The prism correction can be applied as desired and has no influence on the optical corrections. An upper and/or a lower zone of the contact lens that is not utilized for optical purposes can be used for this correction.
In a first embodiment, the contact lens according to the invention is embodied as a bifocal lens and has a $5 near-vision zone and a distance-vision zone as correction zones.
In other embodiments, the contact lens according to the invention is embodied as multifocal lens. By way of example, it has respectively at least one correction zone for nearby, the middle distance and the long distance.
Since there are no intermediate zones between the individual correction zones in either the bifocal lens or the multifocal lens, even in the case of a large correction difference between the individual correction zones, good visual acuity is ensured in all correction zones. This applies even in the case of small pupil diameters. Compared to varifocal spectacles, a clearer image is obtained.
In a preferred embodiment, the correction center is situated outside of the correction zones, i.e. outside of the near-vision, the distance-vision and the possibly present mid-vision zone. An advantage of this embodiment is that the surface design can be perfected during the production of the contact lens. This embodiment can be used not only for bifocal and multifocal contact lenses, but also for contact lenses that have a single correction and hence only a single optically effective correction zone.
In this embodiment, the contact lens or the geometry of the correction area thereof forms an eccentric circle-shaped section from the surface of an imaginary rotational solid. The rotational axis of the rotational solid passes at least approximately through the center of a ball corresponding to the inner face of the lens and is pivoted at least so far upward that it does not pass through the surface of the imaginary ball within the optically utilized surface of the lens. At most, it is pivoted so far upward that the processing tool that rotates about the rotational axis (also referred to as correction axis leaves enough free space for a lens holder for producing the lens.
Thereby it can be achieved that there is no production-technical-dependent center on the optically utilized surface of the contact lens. Here too, a continuous but abruptly separated arrangement of correction zones that adjoin one another is obtained, and hence there are no intermediate zones. Here too, the respectively active correction regions are enlarged in the vertical direction thanks to the eye movement, and so good visual acuity is achieved into the distance and nearby.
Thanks to the horizontal subdivision of the correction zones, broad, integral areas are available per correction zone, which allows a continuously increasing utilization of the correction zones if the pupil size increases. As a result, the effective luminosity is additionally increased in the case of good visual acuity.
The part of the eccentric imaginary rotational solid relevant to the contact lens is defined by a ball in the case of a single correction and by a ball segment and three or four annular ball sections in the case of a multifocal correction.
The imaginary balls on which the imaginary rotational solid is based preferably have a spherical shape. In order to achieve a cylindrical correction, these balls have an ellipsoidal shape. This is achieved by the correction radii of the correction zones being placed outside of the correction axis of the rotational solid. Here, these radii are preferably within a plane set by the correction axis.
It is a further object of the invention to create a production method for contact lenses that allows optimized visual acuity, even in the case of presbyopia.
This object is achieved by a production method having the features of claim 15.
These contact lenses according to the invention can more particularly be embodied as hard, semi-hard or soft lenses.
It is furthermore advantageous that these contact lenses according to the invention can he produced in a simple manner.
Further embodiments are specified in the dependent claims.
In The following text, preferred embodiments of the invention will be described on the basis of the drawings, which merely serve for explanatory purposes and should not be construed as restrictive. In the drawings:
a shows a bifocal contact lens according to the invention during intended use on a human eye;
b shows a longitudinal section through
a shows a trifocal, contact lens according to the invention in the intended usage position on a human eye;
h shows a longitudinal section through
a shows a contact lens as per the prior art in a first embodiment;
b shows a contact lens as per the prior art in a second embodiment;
c shows two contact lenses as per the prior art in a third embodiment; and
d shows two contact lenses as per the prior art in a fourth embodiment.
Identical parts have been provided with the same reference signs,
a shows a first embodiment of a contact lens 5 according to the invention;
The pupil of the eye has been provided with reference sign 2; the cornea respectively the eyeball with reference sign 3. The center of the cornea 3 respectively the pupil 2 is provided with the reference sign 1.
The contact lens 5 preferably has a circular layout. Its circle center point 4 preferably coincides with the center point 1 of the pupil 2 when the user looks forward in a relaxed manner. Hence, the contact lens 5 can be subdivided into an upper and a lower region with respect to the circle center point 4 thereof.
The contact lens 5 has a near-vision zone 10 and a.
distance-vision zone 8. Both zones 8, 10 preferably have a design that is circular, elliptical, oval or of a similar shape. They are preferably applied without an intermediate zone. The two zones 8, 10 lie concentrically with respect to one another, with the distance-vision zone 8 being situated within the near-vision zone 10. Hence, the distance-vision zone 8 has a smaller radius than the near-vision zone 10. The common center of these two zones has been provided with the reference sign 6 in
The near-vision zone 10 extends over a broad region of the contact lens 5, i.e. it extends both in the upper and in the lower region. It preferably extends almost to the edge of the contact lens 5. In the lower region, it merges into a free zone 11, which is not relevant from an optical point of view.
By contrast, the distance-vision zone 8 is preferably only in the upper region of the contact lens. It is preferable for the circle center point 4 of the lens 5 to lie at the lowermost edge of the distance-vision zone 8. However, it can also be situated near to, within or outside of the distance-vision zone 8.
By way of example, the diameter of the contact lens is 10 mm in the case of a pupil, diameter of 3 mm and an iris diameter of 11.5 mm. The distance-vision zone preferably has a diameter of 4.0 mm in this case, and the breadth of the near-vision zone is approximately the same and the diameter thereof is slightly smaller than the diameter of the contact lens.
It is possible to identify in
In the position as per
The contact lens 5 is preferably matched to the outer edge of the cornea 3 such that it can be displaced upwards and downwards by at least 0.5 mm during the above-described upward and downward movements of the eyeball.
a and 5b illustrate a further embodiment of the contact lens 5 according the invention. This is a trifocal contact lens, which therefore has three different optical correction regions.
Here the correction zones 8, 9, 10 also have a circle-like design, more particularly a design that is circular, elliptical or oval. They are embodied in a concentric manner and therefore have a common geometric center on the lens surface—the correction center 6. According to the invention, this correction center 6 once again lies eccentrically with respect to the center point 4 of the lens 5. In the intended usage position, it is situated above this center point 4.
The trifocal contact lens 5 has a distance-vision zone a mid-vision zone 9 and a near-vision zone 10. Furthermore, there is a free zone 11, which is not used from an optical point of view, under the near-vision zone. The distance-vision zone 8 and near-vision zone 10 are arranged as in the first example. The mid-vision zone 9 is situated between the distance-vision zone 8 and near-vision zone 10.
The lower edge of the distance-vision zone 8 preferably ends at a distance from the center point 4 of the contact lens 5. As a result, this center point 4 lies in the region of the mid-vision zone 9.
According to
An at least approximately ball-shaped rotational solid is illustrated in
Hence, the contact lens 5 forms a circular section 31 (calotte) of the imaginary rotational solid 24. The rotational, axis 25 of the rotational solid. 24 lies at an angle 27 to the axis 29 of the lens 5. In this case, the rotational axis 25 is pivoted upwards in respect of the lens axis 29. The common correction center 6 of the optically effective concentric correction zones 8, 9, 10 in this case lies outside of the lens body 5, as can be identified from
In this case, the correction zones 8, 9, 10 are also circle-like, more particularly circular, elliptical or oval. They are concentric with respect to one another and merge continuously, and cleanly separated, into one another. There are no intermediate zones present in this case either. Their common transition diameters are illustrated in the figures with reference signs 35 and 36. The transition diameter of the near-vision zone 10 to the mid-vision zone 9 is denoted by 36. The transition diameter from the mid-vision zone 9 to the distance-vision zone 8 is denoted by 35.
As per
It is possible to identify from
Since the near-vision zone 10 is situated at the bottom, the radii 19, 23, 20 become shorter from top to bottom. In order to achieve this, the start point 32, 33, 34 of the radii 19, 20, 23 on the correction axis should be displaced upwards, which results in a change of the start angle with respect to the end angle of the upper zone. This is illustrated in
Cylindrical corrections are achieved by displacing the centers 32, 33, 34 of the correction radii 19, 20, 23 outward or inward along the correction axis 25. Hence, the resultant rotational solid 24 becomes slightly ellipsoidal. Prism corrections required as a result of the eye position are achieved by pivoting 30 the lens holder 28 about, the center 4 of the contact lens in the vertical or horizontal direction.
Weight corrections for aligning the lens can be made in this case by changing the radius, as required, in the free zones 11 and 11′, which are not used from an optical point of view. By pivoting 26 the lens holder about the center 4 of the lens 5 the whole lens surface can be set in the vertical direction such that an overweight of the lower lens part for the correct alignment of the lens is achieved or increased.
In
In
The contact lens according to the invention ensures optimized visual acuity without intermediate zones, particularly in the case of presbyopia. Moreover, it can be produced in a simple and cost-effective fashion.
Number | Date | Country | Kind |
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1507/09 | Sep 2009 | CH | national |
915/10 | Jun 2010 | CH | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CH10/00232 | 9/28/2010 | WO | 00 | 3/29/2012 |