CA2043038A1 - Lens for prebyopia free from short distance and intermediate distance aberration - Google Patents
Lens for prebyopia free from short distance and intermediate distance aberrationInfo
- Publication number
- CA2043038A1 CA2043038A1 CA 2043038 CA2043038A CA2043038A1 CA 2043038 A1 CA2043038 A1 CA 2043038A1 CA 2043038 CA2043038 CA 2043038 CA 2043038 A CA2043038 A CA 2043038A CA 2043038 A1 CA2043038 A1 CA 2043038A1
- Authority
- CA
- Canada
- Prior art keywords
- lens
- aberration
- curvature
- presbyopia
- free
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a lens for presbyopia free from short distance and intermediate distance aberration for use in correcting an old-age eyesight.
In the lens for presbyopia with a front lens face having a smaller radius of curvature than a rear lens face, a lens face has a refractive index successively corrected as the lens face extends radially outwardly away from a geometric center of the lens so that lateral magnifications for all principal rays always equal a lateral magnification for a paraxial range.
This construction is entirely free from distortional aberration, and secures a greatly enlarged range of distinct vision.
This invention relates to a lens for presbyopia free from short distance and intermediate distance aberration for use in correcting an old-age eyesight.
In the lens for presbyopia with a front lens face having a smaller radius of curvature than a rear lens face, a lens face has a refractive index successively corrected as the lens face extends radially outwardly away from a geometric center of the lens so that lateral magnifications for all principal rays always equal a lateral magnification for a paraxial range.
This construction is entirely free from distortional aberration, and secures a greatly enlarged range of distinct vision.
Description
20~3038 LENS FOR PRESB~OPIA FREE FROM SHORT DISTANCE
AND INTERMEDIATE DISTANCE ABERRATION
SUMMARY OF THE INVENTION
This invention relates to a lens for presbyopia free from short distance and intermediate distance aberration for use in correcting an old-age eyesight.
In the lens for presbyopia with a front lens face having a smaller radius of curvature than a rear lens face, a lens face has a refractive index successively corrected as the lens face extends radially outwardly away from a geometric center of the lens so that lateral magnifications for all principal rays always e~ual a lateral magnification for a paraxial range.
This construction is entirely free from distortional aberration, and secures a greatly enlarged range of distinct vision.
BACKGROUND OF THE INVENTION
When presbyopia develops with the crystalline lens in the eyeball has a weakening adjusting power, accom-modation for seeing a close object becomes impossible.
' ~
20~3~38 In this case, generally, spectacles having convexlenses may be used to compensate for the adjusting power.
An example of known convex lenses for presbyopia is shown in Fig. 5. This is a lens 50 for presbyopia with a front face 5OF having a radius of curvature r(l) smaller than a radius of curvature r(2) of a rear face 5OR thereof.
Specifically, take a lens of two degrees or diopters for example, the smaller radius of curvature r(l) is set to 116.754mm, and the larger radius of curvature r(2) to 218.667mm.
In the illustrated known lens for presbyopia, the above radii of curvature r(l) and r(2) are both fixed radially outwardly from a geometric center 51 of the lens 50. Therefore, the ratio of size (lateral magni-fication) between an object and a virtual image seen through the lens 50 varies with the position of the object, which results in a distortional aberration.
This phenomenon is the more salient the higher is the degree of the lens.
In addition, as shown in hatching in Fig. 5, the ~.
:, . ~ . . . .
20~3~38 conventional lens 50 provides a narrow range of dis-tinct vision. When, for example, the user wears lenses of two degrees, a corrected near point on an optical axis a is at a distance of 300mm (which is a distance from the diaphragm of an eyeball 52), and a corrected far point is at a distance of 504mm (the focal length of the lens) assuming that the far point is at infinity when seen in the naked eye of the user. The range of distinct vision is narrow with the near point at 300mm and the far point at 504mm also when the looking direction of the eye ball forms an angle 01 or ~2 of 30 degrees with the optical axis a. This phenomenon is the more salient the higher is the degree of the lens.
Thus, when the lens 50 of the conventional con-struction is used, the range of distinct vision islimited to short distances, and an image becomes deformed by the distortional aberration. This results in the disadvantages of the eyes becoming fatigued after a long period of use in the absence of a comfort-able visual sense.
. ~ ~
` 2~3038 OBJECTS OF ~HE INVENTION
A principal object of this inventlon is to providea lens for presbyopia free from short distance and intermediate distance aberration, which involves no distortional aberration and realizes a greatly in-creased range of distinct vision.
Another object of this invention is to provide a lens for presbyopia free from short distance and intermediate distance aberration, which, when used, involves no deformation of an object and realizes a comfortable visual sense to cause little fatigue of the eye after a long period of use.
Other objects of this invention will be apparent from the following description of the preferred embodi-ment.
BRIEF DESCRIPTION OF THE ~RAWINGS
The drawings show an embodiment of this invention,in which:-Fig. 1 is an explanatory view of a lens for presbyopia free from short distance and intermediatedistance aberration according to this invention, .
Fig. 2 is an explanatory view showing a state of a front face of the lens before a correction, Fig. 3 is an explanatory view showing a state of the front face of the lens after the correction, Fig. 4 is an explanatory view showing a range of distinct vision of the lens according to this inven-tion, and Fig. 5 is an explanatory view showing a range of distinct vision of a conventional lens.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A lens with a front face having a corrected refractive index will be described in detail as an embodiment of this invention with reference to the drawings.
The drawings show a lens for presbyopia free from short distance and intermediate distance aberration.
In Fig. 1, a lens 11 for presbyopia defines a front face llF having a radius of curvature smaller than a radius of curvature r~2) of a rear face llR thereof.
The radius of curvature r'(l) of the front face llF of the lens 11 is successively corrected as the front face : .
.. . ~ .
, . .
extends radially outwardly away from a geometric center of the lens 11, so that the radius of curvature r'(l) progressively increases to have a lateral magnification for all principal rays equaling a lateral magnification for a paraxial range.
Figs. 1 and 2 show a radius of curvature r(l) prior to the correction in phantom lines. Figs. 1 and 3 show the radius of curvature r'(l) after the correc-tion in solid lines. The radius of curvature r(l) is corrected such that the radius of curvature r'(i) is progressively greater than the radius of curvature r(l) as the front face llF of the lens 11 extends radially outwardly away from the geometric center 12 of the lens.
A specific construction of the lens 11 for presbyopia will be described hereinafter, taking a lens of two degrees fro example.
When the lens 11 is used as shown in Fig. 1, a distance E'P' on an optical axis a between the front face of the diaphragm of an eyeball 13 and the rear ; face Rll of the lens 11 is set to 18mm, the lens 11 has a thic~ness d(l) on the optical axis a set to 3mm, a ', "
, - .-21~3~
distance d(0) on the optical axis a between the front face Fll of the lens 11 and an object 14 is 300mm, the radius of curvature r(2) of the rear face llR of the lens 11 is 218.667mm, and the radius of curvature r(l) of the front face Fll of the lens 11 is 116.754mm. A
lateral magnification ~ for a paraxial range is 2.44136 which is derived from the refractive index of air N'(0) which is 1 and the refractive index N'(l) of the lens 11 formed of a transparent acrylic resin which is 1.492. A distance on the optical axis a between the rear face llR of the lens 11 and a virtual image 15 is -731.11mm.
Next, when the height y(0) of the object 14 is lOmm, the radius of curvature r'(l) of the front face llF which is 116.?54mm is corrected to be 116.8539962768555mm so that the virtual image 15 has a - - height y'(3) equaling the above lateral magnification ~, whereby the virtual image 15 having a height y(3) prior to the correction is changed to the height y'(3) which is 24.413mm. Then, the lateral magnification is y'(3)/y(0) = 2.44134.
. . .
20~3~3~
That is, the radius of curvature of the front face Fll of the lens 11 is increased from r~1~ to r'(1) so that a horizontal length x(1) and a vertical length y(1) of coordinates of an intersecting point between a principal ray and the curved face as shown in Fig. 2 are corrected to be a horizontal length x'(1) and a vertical length y'(1) of coordinates of the intersect-ing point between the principal ray and the curved face.
Next, when the height y(0) of the object 14 is 20mm, the radius of curvature r'(1) of the front face llF is corrected to be 116.9539947509766mm so that the virtual image 15 has a height y'(3) equaling the above lateral magnification ~, whereby the virtual image 15 having the height y(3) prior to the correction is changed to a height y'(3) which is 48.44166mm. Then, the lateral magnification B is y'(3)iy(0) = 2.44166.
Next, when the height y(0) of the object 14 is 30mm, the radius of curvature r'(1) of the front face llF is corrected to be 117.453987121582mm so that the virtual image 15 has a height y'(3) equaling the above lateral magnification B, whereby the virtual image 15 , .
, . . .
AND INTERMEDIATE DISTANCE ABERRATION
SUMMARY OF THE INVENTION
This invention relates to a lens for presbyopia free from short distance and intermediate distance aberration for use in correcting an old-age eyesight.
In the lens for presbyopia with a front lens face having a smaller radius of curvature than a rear lens face, a lens face has a refractive index successively corrected as the lens face extends radially outwardly away from a geometric center of the lens so that lateral magnifications for all principal rays always e~ual a lateral magnification for a paraxial range.
This construction is entirely free from distortional aberration, and secures a greatly enlarged range of distinct vision.
BACKGROUND OF THE INVENTION
When presbyopia develops with the crystalline lens in the eyeball has a weakening adjusting power, accom-modation for seeing a close object becomes impossible.
' ~
20~3~38 In this case, generally, spectacles having convexlenses may be used to compensate for the adjusting power.
An example of known convex lenses for presbyopia is shown in Fig. 5. This is a lens 50 for presbyopia with a front face 5OF having a radius of curvature r(l) smaller than a radius of curvature r(2) of a rear face 5OR thereof.
Specifically, take a lens of two degrees or diopters for example, the smaller radius of curvature r(l) is set to 116.754mm, and the larger radius of curvature r(2) to 218.667mm.
In the illustrated known lens for presbyopia, the above radii of curvature r(l) and r(2) are both fixed radially outwardly from a geometric center 51 of the lens 50. Therefore, the ratio of size (lateral magni-fication) between an object and a virtual image seen through the lens 50 varies with the position of the object, which results in a distortional aberration.
This phenomenon is the more salient the higher is the degree of the lens.
In addition, as shown in hatching in Fig. 5, the ~.
:, . ~ . . . .
20~3~38 conventional lens 50 provides a narrow range of dis-tinct vision. When, for example, the user wears lenses of two degrees, a corrected near point on an optical axis a is at a distance of 300mm (which is a distance from the diaphragm of an eyeball 52), and a corrected far point is at a distance of 504mm (the focal length of the lens) assuming that the far point is at infinity when seen in the naked eye of the user. The range of distinct vision is narrow with the near point at 300mm and the far point at 504mm also when the looking direction of the eye ball forms an angle 01 or ~2 of 30 degrees with the optical axis a. This phenomenon is the more salient the higher is the degree of the lens.
Thus, when the lens 50 of the conventional con-struction is used, the range of distinct vision islimited to short distances, and an image becomes deformed by the distortional aberration. This results in the disadvantages of the eyes becoming fatigued after a long period of use in the absence of a comfort-able visual sense.
. ~ ~
` 2~3038 OBJECTS OF ~HE INVENTION
A principal object of this inventlon is to providea lens for presbyopia free from short distance and intermediate distance aberration, which involves no distortional aberration and realizes a greatly in-creased range of distinct vision.
Another object of this invention is to provide a lens for presbyopia free from short distance and intermediate distance aberration, which, when used, involves no deformation of an object and realizes a comfortable visual sense to cause little fatigue of the eye after a long period of use.
Other objects of this invention will be apparent from the following description of the preferred embodi-ment.
BRIEF DESCRIPTION OF THE ~RAWINGS
The drawings show an embodiment of this invention,in which:-Fig. 1 is an explanatory view of a lens for presbyopia free from short distance and intermediatedistance aberration according to this invention, .
Fig. 2 is an explanatory view showing a state of a front face of the lens before a correction, Fig. 3 is an explanatory view showing a state of the front face of the lens after the correction, Fig. 4 is an explanatory view showing a range of distinct vision of the lens according to this inven-tion, and Fig. 5 is an explanatory view showing a range of distinct vision of a conventional lens.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A lens with a front face having a corrected refractive index will be described in detail as an embodiment of this invention with reference to the drawings.
The drawings show a lens for presbyopia free from short distance and intermediate distance aberration.
In Fig. 1, a lens 11 for presbyopia defines a front face llF having a radius of curvature smaller than a radius of curvature r~2) of a rear face llR thereof.
The radius of curvature r'(l) of the front face llF of the lens 11 is successively corrected as the front face : .
.. . ~ .
, . .
extends radially outwardly away from a geometric center of the lens 11, so that the radius of curvature r'(l) progressively increases to have a lateral magnification for all principal rays equaling a lateral magnification for a paraxial range.
Figs. 1 and 2 show a radius of curvature r(l) prior to the correction in phantom lines. Figs. 1 and 3 show the radius of curvature r'(l) after the correc-tion in solid lines. The radius of curvature r(l) is corrected such that the radius of curvature r'(i) is progressively greater than the radius of curvature r(l) as the front face llF of the lens 11 extends radially outwardly away from the geometric center 12 of the lens.
A specific construction of the lens 11 for presbyopia will be described hereinafter, taking a lens of two degrees fro example.
When the lens 11 is used as shown in Fig. 1, a distance E'P' on an optical axis a between the front face of the diaphragm of an eyeball 13 and the rear ; face Rll of the lens 11 is set to 18mm, the lens 11 has a thic~ness d(l) on the optical axis a set to 3mm, a ', "
, - .-21~3~
distance d(0) on the optical axis a between the front face Fll of the lens 11 and an object 14 is 300mm, the radius of curvature r(2) of the rear face llR of the lens 11 is 218.667mm, and the radius of curvature r(l) of the front face Fll of the lens 11 is 116.754mm. A
lateral magnification ~ for a paraxial range is 2.44136 which is derived from the refractive index of air N'(0) which is 1 and the refractive index N'(l) of the lens 11 formed of a transparent acrylic resin which is 1.492. A distance on the optical axis a between the rear face llR of the lens 11 and a virtual image 15 is -731.11mm.
Next, when the height y(0) of the object 14 is lOmm, the radius of curvature r'(l) of the front face llF which is 116.?54mm is corrected to be 116.8539962768555mm so that the virtual image 15 has a - - height y'(3) equaling the above lateral magnification ~, whereby the virtual image 15 having a height y(3) prior to the correction is changed to the height y'(3) which is 24.413mm. Then, the lateral magnification is y'(3)/y(0) = 2.44134.
. . .
20~3~3~
That is, the radius of curvature of the front face Fll of the lens 11 is increased from r~1~ to r'(1) so that a horizontal length x(1) and a vertical length y(1) of coordinates of an intersecting point between a principal ray and the curved face as shown in Fig. 2 are corrected to be a horizontal length x'(1) and a vertical length y'(1) of coordinates of the intersect-ing point between the principal ray and the curved face.
Next, when the height y(0) of the object 14 is 20mm, the radius of curvature r'(1) of the front face llF is corrected to be 116.9539947509766mm so that the virtual image 15 has a height y'(3) equaling the above lateral magnification ~, whereby the virtual image 15 having the height y(3) prior to the correction is changed to a height y'(3) which is 48.44166mm. Then, the lateral magnification B is y'(3)iy(0) = 2.44166.
Next, when the height y(0) of the object 14 is 30mm, the radius of curvature r'(1) of the front face llF is corrected to be 117.453987121582mm so that the virtual image 15 has a height y'(3) equaling the above lateral magnification B, whereby the virtual image 15 , .
, . . .
2~30~
having the height y(3) prior to the correction is changed to a height y'(3) which is 73.24796mm. Then, the lateral magnification B is y'(3)/y(0) = 2.4416.
Thereafter, the height y(0) of the object 14 is successively increased lOmm, and the radius of curva-ture r'(1) of the front face llF is increased as above until y(0) equals 170mm. Only numeric values will be set out for expediency of explanation.
When y(0) is 40mm, r'~1) = 118.1539764404297mm, y'(3) = 97.6602mm, and ~ = 2.4415.
When y(0) is 50mm, r'(1) = 118.9539642333984mm, y'(3) = 122.077mm, and ~ = 2.44154.
When y(0~ is 60mm, r'(1) = 120.0539474487305mm, y'(3) = 146.481mm, and ~ = 2.44136.
When y(0) is 70mm, r'(1) = 121.1539306640625mm, g _ .
- 20~303~
y'(3) = 170.903mm, and ~ = 2.44147.
When y(0) is 80mm, r'(1) = 122.5539093017578mm, S y'(3) - 195.306m~, and ~ = 2.44133.
When y(0) is 90mm, r'(1) = 123.9538879394531mm, y'(3) = 219.731mm, and B = 2.44145.
When y(0) is lOOmm, r'(1) = 125.6538619995117mm, y'(3) = 244.129mm, and ~ = 2.44129.
When y(0) is llOmm, r'(1) = 127.3538360595703mm, y~(3) = 268.551mm, and ~ = 2.44137.
When y(0) is 120mm, r'(1) = 129.25390625mm, y'(3) = 292.957mm, and ~ = 2.44131.
.
20~30~o When y(0) is 130mm, r'(1) = 131.1540222167969mm, y'(3) = 317.386mm, and ~ = 2.44143.
When y(0) is 140mm, r'(1) = 133.254150390325mm, y'~3) = 341.793mm, and ~ = 2.44138.
When y(0) is 150mm, r'(1) = 135.4542846679687mm, y'(3) = 366.194mm, and ~ = 2.4413.
When y(O) is 160mm, r'(1) = 137.6544189453125mm, y'(3) = 390.615mm, and ~ = 2.44134.
When y(0) is 170mm, r'(1) = 139.9545593261719mm, y'(3) = 415.024mm, and ~ = 2.44132.
In this way, the radius of curvature r'(1) of the front face F11 of the lens 11 is successively increased "~ ~
20~3038 so that the lateral magnifications for all the princi-pal rays equal the lateral magnification B for the paraxial range. Since the front face Fll of the lens has a unique, aspherical structure, the distortional aberration is completely eliminated to produce the effect of realizing a lens free from aberration.
In addition, a greatly increased range of distinct vision is secured as shown in hatching in Fig. 4. Take the lens 11 of two degrees for example, the near point on the optical axis a is at 300mm and the far point at 504mm. In a state in which principal rays b form an angle ~1 or 02 of 30 degrees with the optical axis a, the range of distinct vision is greatly increased with the near point at about 373mm and the far point at about 780mm. This effect is the more salient the higher is the degree of the lens.
Thus, when the lens 11 of the above construction is used, there occurs no fluctuation of the image due to movement of the eyeball, and a clear field of view is secured covering from a short distance range to an intermediate range. Thus, a comfortable visual sense is secured and the fatigue of the eye resulting from a ~043~8 long period of use is reduced.
Further, since, as described above, the radius of curvature of the front face F11 of the lens 11 is successively increased (i.e. the refractive index of the lens is successively reduced), the front face F11 projects only a small amount, i.e. has a small swell.
The lens may be thinned by the corresponding amount, which produces the effects of securing a brighter field of view and allowing the lens 11 to be lightweight.
In the foregoing embodiment, the radius of curva-ture of the front face of the lens is successively increased to successively decrease the refractive index of the lens. The correction is not limited to the front face of the lens, but may of course be effected to the rear face only or to both the front and rear faces.
,:
having the height y(3) prior to the correction is changed to a height y'(3) which is 73.24796mm. Then, the lateral magnification B is y'(3)/y(0) = 2.4416.
Thereafter, the height y(0) of the object 14 is successively increased lOmm, and the radius of curva-ture r'(1) of the front face llF is increased as above until y(0) equals 170mm. Only numeric values will be set out for expediency of explanation.
When y(0) is 40mm, r'~1) = 118.1539764404297mm, y'(3) = 97.6602mm, and ~ = 2.4415.
When y(0) is 50mm, r'(1) = 118.9539642333984mm, y'(3) = 122.077mm, and ~ = 2.44154.
When y(0~ is 60mm, r'(1) = 120.0539474487305mm, y'(3) = 146.481mm, and ~ = 2.44136.
When y(0) is 70mm, r'(1) = 121.1539306640625mm, g _ .
- 20~303~
y'(3) = 170.903mm, and ~ = 2.44147.
When y(0) is 80mm, r'(1) = 122.5539093017578mm, S y'(3) - 195.306m~, and ~ = 2.44133.
When y(0) is 90mm, r'(1) = 123.9538879394531mm, y'(3) = 219.731mm, and B = 2.44145.
When y(0) is lOOmm, r'(1) = 125.6538619995117mm, y'(3) = 244.129mm, and ~ = 2.44129.
When y(0) is llOmm, r'(1) = 127.3538360595703mm, y~(3) = 268.551mm, and ~ = 2.44137.
When y(0) is 120mm, r'(1) = 129.25390625mm, y'(3) = 292.957mm, and ~ = 2.44131.
.
20~30~o When y(0) is 130mm, r'(1) = 131.1540222167969mm, y'(3) = 317.386mm, and ~ = 2.44143.
When y(0) is 140mm, r'(1) = 133.254150390325mm, y'~3) = 341.793mm, and ~ = 2.44138.
When y(0) is 150mm, r'(1) = 135.4542846679687mm, y'(3) = 366.194mm, and ~ = 2.4413.
When y(O) is 160mm, r'(1) = 137.6544189453125mm, y'(3) = 390.615mm, and ~ = 2.44134.
When y(0) is 170mm, r'(1) = 139.9545593261719mm, y'(3) = 415.024mm, and ~ = 2.44132.
In this way, the radius of curvature r'(1) of the front face F11 of the lens 11 is successively increased "~ ~
20~3038 so that the lateral magnifications for all the princi-pal rays equal the lateral magnification B for the paraxial range. Since the front face Fll of the lens has a unique, aspherical structure, the distortional aberration is completely eliminated to produce the effect of realizing a lens free from aberration.
In addition, a greatly increased range of distinct vision is secured as shown in hatching in Fig. 4. Take the lens 11 of two degrees for example, the near point on the optical axis a is at 300mm and the far point at 504mm. In a state in which principal rays b form an angle ~1 or 02 of 30 degrees with the optical axis a, the range of distinct vision is greatly increased with the near point at about 373mm and the far point at about 780mm. This effect is the more salient the higher is the degree of the lens.
Thus, when the lens 11 of the above construction is used, there occurs no fluctuation of the image due to movement of the eyeball, and a clear field of view is secured covering from a short distance range to an intermediate range. Thus, a comfortable visual sense is secured and the fatigue of the eye resulting from a ~043~8 long period of use is reduced.
Further, since, as described above, the radius of curvature of the front face F11 of the lens 11 is successively increased (i.e. the refractive index of the lens is successively reduced), the front face F11 projects only a small amount, i.e. has a small swell.
The lens may be thinned by the corresponding amount, which produces the effects of securing a brighter field of view and allowing the lens 11 to be lightweight.
In the foregoing embodiment, the radius of curva-ture of the front face of the lens is successively increased to successively decrease the refractive index of the lens. The correction is not limited to the front face of the lens, but may of course be effected to the rear face only or to both the front and rear faces.
,:
Claims
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a lens for presbyopia with a front lens face having a smaller radius of curvature than a rear lens face, a lens for presbyopia free from short distance and intermediate distance aberration comprising a lens face having a refractive index successively corrected as the lens face extends radially outwardly away from a geometric center of the lens so that lateral magnifica-tions for all principal rays always equal a lateral magnification for a paraxial range.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2043038 CA2043038A1 (en) | 1991-05-22 | 1991-05-22 | Lens for prebyopia free from short distance and intermediate distance aberration |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2043038 CA2043038A1 (en) | 1991-05-22 | 1991-05-22 | Lens for prebyopia free from short distance and intermediate distance aberration |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2043038A1 true CA2043038A1 (en) | 1992-11-23 |
Family
ID=4147636
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2043038 Abandoned CA2043038A1 (en) | 1991-05-22 | 1991-05-22 | Lens for prebyopia free from short distance and intermediate distance aberration |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2043038A1 (en) |
-
1991
- 1991-05-22 CA CA 2043038 patent/CA2043038A1/en not_active Abandoned
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