Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Reexamination Certificate
2000-08-04
2001-11-27
Schwartz, Jordan M. (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
Reexamination Certificate
active
06322213
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a progressive multifocal contact lens suitable for compensating presbyopia or, more generally, an ametropia associated with presbyopia.
The state-of-the-art multifocal contact lenses for the purposes set out above comprise physically defined optical zones for generating a double focalization of a single object.
In particular, GB 2288033 A reveals a contact lens for correcting presbyopia in which the central part is aspherical and corrects the near vision, while the peripheral annular part is spherical and corrects the far vision, where the aspherical part is multifocal, while the spherical part has a single focus.
The principal drawback of the known lenses is that a sufficiently valid vision is obtained only if and when the lens achieves and maintains adequate dynamics, that is to say, an adequate movement on the surface of the cornea. But even when this result is obtained, it will be accompanied by a fractionation of the radiant energy flux, which is effectively divided by the two areas of different dioptric power with a consequent loss of visual capacity of the wearer of the lens as regards mesoptic and nocturnal vision.
SUMMARY OF THE INVENTION
A long series of experiments has led to the present invention, which is capable of obviating these drawbacks and providing advantages that will be explained in due course. The invention is a progressive multifocal contact lens that makes the optical power vary with respect to the base dioptric power from the centre to the periphery of the entire optical zone, the power variation being such that it first diminishes, then remains constant and eventually rises again; this lens is capable of compensating the optical effect of presbyopia or other anomalies of the accommodation system.
The inventors deem that the new and unforseeable results obtained by their experiments could find explanation in the capacity of the combined system constituted by the eye and the brain of selecting the most suitable focal point for furnishing a clear perception of what the viewer wants to see within the scenario that engages his attention. Starting from what is currently known about the image perception mechanism, the inventors have- as it were- followed the path of the light rays backwards from the retina to the external surface of the contact lenses. It was simulated with the help of a computer and, using software specially created for this purpose, the optical zone of the contact lens was then processed and re-elaborated to define an uninterrupted bundle of clearly perceptible focal zones; this led to the construction of a rather complex surface, but which furnishes a far vision exactly equal to that of a normal monofocal contact lens and an excellent vision at both intermediate distances (desk, computer)and near distances (books, wristwatch, etc.)
The present description employs a number of terms that are to be conventionally understood as having the following meanings:
(i)—lens—stands for contact lens;
(ii)—internal—and—external—, when referred to the surfaces or the profiles of a lens, stand respectively for the side in contact with the eye and the side facing away from it;
(iii)—progression—indicates the fundamental characteristic of the invention: it is the function according to which the optical power of the lens varies with the distance from the centre and right through to the periphery of the lens;
(iv)—profile—of the lens is used to indicate the profile, generally the external one, that is presented by a radial section of a lens (the terms—profile—and—external surface, or internal surface—may at times be used indifferently to express one and the same concept;
(v) the—base dioptric power—is used herein for what is also known as the neutral power or the value of the ametropia or the far vision power of the lens;
(vi) the diagramme in which the progression of the lens is to be represented has the distance from the centre to the periphery of the optical zone of the lens as its abscissa and the optical power of the lens as ordinate (it will be the diagram of a rotation figure around the centre of the lens);
(vii) the expressions—to see from close by—and—to see from far away—are simplified into respectively—for near vision—and—for far vision—.
The progression has the characteristic of presenting three tracts, each joined to its immediate predecessor: a) a first tract in which the lens functions for near vision, which commences from a peak at the centre to decrease very rapidly to the base dioptric power; b) a second tract in which the lens functions for far vision and remains substantially parallel to the abscissa at the level of the base dioptric power; c) a third tract comprising a first progressively increasing part and a second part parallel to the abscissa, corresponding to the powers at which the lens functions progressively in the first part for intermediate distances and in the second part in a constant manner for near vision.
It has been found that the first and the third tract, a) and c), separated by the second tract, b), influence each other and are both indispensable for furnishing an adequate vision for intermediate distances and for nearby.
It can be readily understood that the progression creates a series of concentric optical zones on the surface of the lens: a first central and circular zone and others in annular form of greater or lesser width in the radial direction, each of the latter obviously having equal optical characteristics throughout its radial and circular extension, and it can also be seen that, for each person suffering from a particular refraction status, the progression, though always characterized by the aforesaid three tracts, will have a peculiar pattern of its own, generally different from all others.
The lens of the invention can be either of the soft, hydrogel or rigid gas-permeable type.
REFERENCES:
patent: 4976534 (1990-12-01), Miege et al.
patent: 5024517 (1991-06-01), Seidner
patent: 5112351 (1992-05-01), Christie et al.
patent: 5530491 (1996-06-01), Baude et al.
patent: 5682223 (1997-10-01), Menezes et al.
patent: 5691797 (1997-11-01), Seidner et al.
patent: 6221105 (2001-04-01), Portney
patent: 0 822 439 A1 (1998-02-01), None
patent: 2 288 033 A (1995-10-01), None
Altieri Andrea
Filippo Alessandro
Euro Lens Technology S.p.A.
Schwartz Jordan M.
Wenderoth , Lind & Ponack, L.L.P.
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