Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2002-06-20
2004-09-21
Epps, Georgia (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
C351S168000
Reexamination Certificate
active
06793340
ABSTRACT:
The present invention relates to a progressive ophthalmic lens and in particular to a progressive ophthalmic lens exhibiting improved functionality and ease of adaptation, particularly for the first-time or part-time wearer, and taking into account wearer sensitivity to swim, 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.
However, prior art progressive lenses present the wearer with significant adaptation difficulties. For example, a wearer who utilises progressive lenses for reading purposes may generally be inconvenient t)y the limited width of vision for near tasks. Similarly, new progressive spectacle wearers may be sensitive to swim and may be unable or unwilling to learn new head postures dictated by prior art progressive lenses.
It would be a 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 intermediate and near tasks in particular and thus make adaptation to a progressive prescription easier.
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 ophthalmic 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 lens surface including
a relatively high, relatively wide lower viewing zone; and
a relatively wide intermediate zone.
The present invention accordingly provides a progressive ophthalmic lens element exhibiting a balance in zone sizes which provides the wearer with significantly improved near and intermediate vision, thus making spectacles including the progressive ophthalmic lenses more acceptable to the first time or part-time wearer, or a wearer with a near vision priority, and making adaptation thereto a much simpler task.
We may estimate the size of she zone on the lens surface available for clear vision by ray tracing the lens in the as worn configuration for a specific object distance and calculating the area within an Add/4 diopter contour of the RMS power error inside a circle of the 22 m radius centred on the geometric centre (GC).
Preferably, the area of the lower viewing zone when ray traced to a 0.4 m object distance is over 150 mm
2
.
In a further preferred aspect, the progressive lens design according to this aspect of the present invention may be such that the ratio of the area of clear vision of the upper (or distance) viewing zone to the lower (or near) viewing zone is in the range between approximately 2.50 and 3.00.
This clear vision size ratio is indicative of effective relative zone sizes and illustrates the improved balance of zone sizes between the distance and near viewing zones in the ophthalmic lens elements for wearers with a near vision priority according to the present invention.
By the term “Add” as used herein we mean surface addition power of the lens element.
In a further preferred aspect the progressive design lens according to this aspect of the present invention includes a surface design of the peripheral regions of the lens to reduce or minimise the phenomenon of “swim”. By the term “swim” as used herein, we mean wearer perception of the unnatural movement of objects within the visual field during dynamic visual tasks, which may lead to a sense of unsteadiness, dizziness or nausea.
The applicants have found that the lens surface areas that are critical for reducing the swim sensation are within a pair of generally horizontally disposed opposed segments approximately ±22.5° above and below a generally horizontal axis passing through the fitting cross.
The opposed segments may have a radius of approximately 15 mm from the fitting cross, preferably approximately 20 mm, more preferably approximately 25 mm.
The minimisation of the swimming sensation may be achieved by reducing optical aberrations contributing to swim. A surface correction(s) may provide a reduction in the sagittal addition power within the opposed segments. The surface(s) may be such that the difference between maximum and minimum sagittal addition power is less than approximately 0.75*Add diopters. This may significantly reduce the phenomenon of swim for a wearer, in use.
This may have the result of increasing blur in the peripheral regions of the lower (or near) viewing zone. However, such blur increase in these regions is an acceptable trade-off in achieving wearer satisfaction with the progressive lenses.
In a still further preferred aspect of the present invention, the progressive lens design may exhibit a small amount of addition power (eg. 0.05 D to 0.4 D), proximate the fitting cross depending on the nominal addition power of the lens element and the base curve.
Applicants have found that the introduction of a small amount of addition power at the fitting cross aids the wearer in adapting to the progressive ophthalmic lens, particularly in respect of intermediate vision. The corridor of the intermediate viewing zone is thus effectively extended a small distance into the upper (or distance) viewing zone, allowing peripheral blur values to be reduced and the zone available for clear vision at intermediate distances to be increased.
It will be understood that the ophthalmic lens element according to the present invention may form one of a series of lens elements.
Accordingly, in a further aspect of the present invention, there is provided a series of progressive ophthalmic 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 ophthalmic lens series including
lens elements having a base curve suitable for use in providing a range of distance prescriptions for one or more of emmetropes, hyperopes and myopes, each lens element differing in prescribed addition power and including a progressive design including
a relatively high, relatively wide lower viewing zone and
a relatively wide intermediate zone; the dimensions of the intermediate and lower viewing zones being related to the prescribed addition power of the wearer.
The present invention accordingly relates to a progressive ophthalmic 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 swim and natural eye movements. The progressive lens element within the series also exhibits a distance
ear zone balance more appropriate for a part-time wearer or a wearer with a near vision priority than those provided by ge
Fisher Scott Warren
Morris Michael Alan
Pope David Robert
Varnas Saulius Raymond
Burns Doane , Swecker, Mathis LLP
Epps Georgia
Sola International Holdings Ltd.
Thomas Brandi
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