Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2002-02-28
2003-11-25
Sugarman, Scott J. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
Reexamination Certificate
active
06652096
ABSTRACT:
The present invention relates to a progressive opthalmatic lens and in particular to a progressive opthalmatic lens exhibiting reduced sensitivity to fitting errors, improved functionality and ease of adaptation, designed to more closely follow the natural eye movements of the wearer and taking into account wearer sensitivity to blur, and to a process for producing such lenses.
Numerous progressive lenses are known in the prior art. Progressive lenses have heretofore been designed on the basis that they have distance, near and intermediate viewing zones. The intermediate zone joins the near and distance zones in a cosmetically acceptable way, in the sense that no discontinuities in the lens should be visible to people observing the lens of the wearer. The design of the intermediate zone is based on a line called the “eye path” along which the optical power of the lens increases more or less uniformly.
Prior art progressive lenses do not address the depth of field factor, which defines wearer sensitivity to blur. They also did not attempt to tailor the blur gradients to wearer preferences.
A further disadvantage of prior art progressive lenses is that they are difficult to fit. Such lenses must be fitted to a carefully measured pupillary height relative to the lower frame edge, and to a carefully measured pupillary distance relative to the nasal frame edge. Errors of as little as 1 or 2 mm in either measurement can cause significant reduction in lens utility.
It would be a significant advance in the art if a progressive opthalmatic lens could be designed with reduced sensitivity to horizontal fitting errors (such as errors in pupillary distance measurement of the wearer) and vertical fitting height errors ascribed to frame and face conformation measurement errors. This would make such lenses more similar in ease of fitting to single vision reading lenses.
It would be a further significant advance in the art if the progressive lens could more closely relate to the requirements of the individual wearer and to the natural eye movements of a wearer in performing distance, intermediate and near tasks.
Accordingly, it is an object of the present invention to overcome, or at least alleviate, one or more of the difficulties and deficiencies related to the prior art. These and other objects and features of the present invention will be clear from the following disclosure.
Accordingly, in a first aspect of the present invention, there is provided a progressive opthalmatic lens element including a lens surface having
an upper viewing zone having a surface power corresponding to distance vision,
a lower viewing zone having a greater surface power than the upper viewing zone to achieve a refracting power corresponding to near vision; and
an intermediate zone extending across the lens element having a surface power varying from that of the upper viewing zone to that of the lower viewing zone and including
a corridor of relatively low surface astigmatism; the corridor exhibiting a power progression from that of the upper viewing zone to that of the threshold of the lower viewing zone,
the corridor and lower viewing zone exhibiting a power progression profile having at least two segments the slopes of which being related at least in part to the prescribed addition power and/or the depth of focus of the wearer.
It will be understood that the present invention permits the progressive lens design to be tailored to improve functionality and/or ease of adaptation, depending on the wearer's prescription.
It will be understood that the opthalmatic lens element according to the present invention may form one of a series of lens elements. The lens element series may be of the type described in International patent application PCT/EP97/00105, to applicants, the entire disclosure of which is incorporated herein by reference.
The present invention accordingly relates to a progressive opthalmatic lens series exhibiting improved functionality and ease of adaptation, as it takes into account factors including one or more of the following: wearers' sensitivity to blur, natural eye movements, preferences for the blur gradients across the boundaries of the peripheral zones. These factors may be dependent on the wearer's prescription.
Accordingly, in a further aspect of the present invention, there is provided a series of progressive opthalmatic lens elements, each lens element including a lens surface having
an upper viewing zone having a surface power to achieve a refracting power corresponding to distance vision;
a lower viewing zone having a greater surface power than the upper viewing zone to achieve a refracting power corresponding to near vision; and
an intermediate zone extending across the lens element having a surface power varying from that of the upper viewing zone to that of the lower viewing zone and including a corridor of relatively low surface astigmatism;
the progressive opthalmatic lens series including
a first set of lens elements having at least one base curve suitable for use in providing a range of distance prescriptions for myopes, emmetropes or hyperopes, each lens element within a set differing in prescribed addition power and including a progressive design, the corridor and lower viewing zone exhibiting a power progression profile having at least two segments the slopes of which are related to the prescribed addition power and/or depth of focus of the wearer;
each lens element within a set
having an addition power of from approximately 0.75 D to 1.50 D, exhibiting a relatively shallow power progression in the first segment and a relatively steep power progression in the second segment; and
having an addition power of from approximately 1.75 D to 3.00 D, exhibiting a relatively steep power progression in the first segment and a relatively shallow power progression in the second segment.
The opthalmatic lens element, at low addition powers, for example from approximately 0.75 D to 1.50 D, where accommodation reserve is relatively high, may exhibit a relatively shallow power progression within the upper part of the corridor; and a relatively steep power progression from the lower part of the corridor to the near measurement point (NMP). This makes a functionally better progressive lens for those wearers that do not have much need for addition power when viewing objects at intermediate distances. They have sufficient amount of accommodation to be able to view most objects at intermediate distances through the distance zone of the lens.
The opthalmatic lens element, at high addition powers, for example from approximately 1.75 D to 3.00 D, may exhibit a relatively steep power progression within the upper part of the corridor; and a relatively shallow power progression from the lower part of the corridor to the near vision measurement point.
It will be understood that the provision of, for example, a relatively steep power progression within the upper part corridor of the opthalmatic lens element provides an increased level of freedom in lens design within the lower or near viewing zone, thus permitting an improvement in optical quality within the zone. This is very important for high add wearers that are likely to lead a more sedentary lifestyle and have high demands on the near vision performance of their spectacles.
It will be further understood that the opthalmatic lens element according to this aspect of the present invention exhibits a power progression profile which is divided into at least two segments. The slopes of the segments are related to the addition power, accommodation reserve, and the depth of focus of the wearer.
The two segments may exhibit a length ratio, for example, of approximately 2:1): fitting cross (FC) to the “highest reading point” (HRP) and the tail between the HRP and the full addition power at the near vision measurement point (NMP).
The first segment may be characterised by a steep rise of power making the effective length of the corridor very short, for example approximately 11 mm, for addition powers up to approximately 2.50 D and increasing
Miller Anthony Dennis
Morris Michael Alan
Varnas Saulius Raymond
Sola International Holdings Ltd.
Sugarman Scott J.
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