Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1986-04-21
1990-03-06
Arnold, Bruce Y.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
G02C 706
Patent
active
049060902
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to half-eye spectacles.
Half-eye spectacles are spectacles where only that part of the spectacle lens is fitted into the spectacle frame which is not used for distance vision. With the known half-eye spectacles, spherical or toric single vision lenses are used where the "upper lens half" has simply been left off.
The optical power of the known half-eye spectacles is chosen in such a way that it will allow the spectacle wearer clear vision at short distances, i.e. at typical reading distances of about 40 cm. However, this means that the known half-eye spectacles have the disadvantage that they do not permit vision at intermediate distances, that is, for example, at distances of about one meter, with the accustomed visual comfort.
The object of the present invention is to provide half-eye spectacles which will also support visual accommodation in the intermediate area.
In accordance with this invention the focal power of the half-eye spectacle lens increases progressively from the upper rim area towards the bottom of the lens to that value which the spectacle wearer requires for near vision. At least one surface contributes to this increase in the focal power.
In an advantageous further development of the present invention, the prismatic power at the upper rim of the half-eye spectacles is zero so that no irritating image jump occurs when the gaze of the spectacle wearer is lowered (or raised) when he changes his visual direction from distance vision to near vision (or vice versa).
The power of the spectacle lens in the upper rim area may be 0 D. It is, however, particularly advantageous if the spectacle lens has a power other than zero in the upper rim area as the typical wearer of half-eye spectacles, an emmetropic presbyope, looks over the upper rim of the half-eye spectacles when looking into the distance. Only when his gaze is lowered, when he will typically want to see objects at medium visual distances, will the half-eye spectacle wearer look through the upper part of the progressive half-eye spectacles. Half-eye spectacles with a power other than zero in the area of their upper rim will then allow him clear vision for these finite distances, which the spectacle wearer can no longer manage alone through accommodation.
Furthermore, an upper rim area with power other than zero also has the advantage that it increases the "effective" addition of the spectacle lens--in contrast to the "surface theoretical" addition--by the value of the power in the upper rim area. This means that half-eye spectacles with an addition, i.e. with a difference between the power at the near reference point and the distance reference point (no longer present with half-eye spectacles) of 2 D and a power of 1 D in the upper rim area, will have the same power for the spectacle wearer as a surface with an addition of 3 D and a power of 0 D in the upper rim area. However, such a power of about 1 D is required by the emmetropic presbyope just for clear vision at infinite distances of about 1 m. In this way, he will find the corresponding powers on the surface of the half-eye spectacles for this distance and all short distances.
Nevertheless, the progressive surface of the half-eye spectacles still must only be calculated as if it had an addition of only 2 D. Such a surface with an addition of (for example) only 2 D has the advantage over a surface with an addition of (for example) 3 D that the progression corridor is wider: According to Minkwitz' proposition the width of the progression corridor (or the so-called progressive channel) is namely inversely proportional to the power increase.
Naturally both surfaces of the spectacle lens according to this invention for half-eye spectacles can contribute to the power increase from the upper rim area towards the lower portion of the lens. This is, however, of particular advantage if only one surface contributes to this power increase while the other surface has a spheric or toric design. In this way not only is an espec
REFERENCES:
patent: 4315673 (1982-02-01), Guilino et al.
patent: 4592630 (1986-06-01), Okazaki
Arnold Bruce Y.
Callaghan Terry S.
Optische Werke G. Rodenstock
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