Patent Publication Number: US-2019196224-A1

Title: Dual defocus lens

Description:
This application claims priority for Taiwan patent application no. 106145914 filed on Dec. 27, 2017, the content of which is incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention is related to a lens, particularly related to a dual defocus lens. 
     Description of Related Art 
     In order to solve the poor vision more efficiently and correctly, the design of the lens is focused on the correcting the refractive error instead of on improving the visual resolution. Take the myopia as an example, the images of different incident angles should be imaged on different positions of the retina  21  having a curved surface. The retinal image is quite poor owing to the only one diopter provided via the lens  5   a.  No different incident angles of lights can be generated via the lens  5   a.  The light L through the lens  5   a  is split and only some part of the split light corresponding to the central region of the retina  21  can form a clear retinal image while other part of the split light is focused behind the retina  21  (illustrated as the dashed line) cannot form the retinal image at all. As illustrated in  FIG. 1A , the retina  21  will deform backwards after long-time usage of the lens  5   a.  Consequently, the diopter cannot be improved, and the vision gets worse either. 
     Later, a multifocal lens is developed and is illustrated in  FIG. 1B . Generally, the multifocal lens  5   b  comprises many concentric-ring optical regions, as illustrated as the dashed line. The inner central region  513  is surrounded via the outer concentric-ring regions  511  and  512 , as illustrated in  FIG. 1B . The inner central region  513  has a first focal length, the outer concentric-ring region  511  has a second focal length and the concentric-ring region  512  has a third focal length, wherein the first, second and the third focal lengths are different. Hence, the light L passing through the inner central region  513  images on the corresponding region of the retina  21 ; the light L passing through the outer concentric-ring regions  511  and  512  image on the corresponding region of the retina  21  as well. The multifocal lens  5   b  can be suitable for both myopia vision and hyperopia vision, however, the rapid and frequent of relaxation and contraction of the ciliary muscle lead to instant vertigo or short-sighted blindness during the transition of myopia vision to hyperopia vision or hyperopia vision to myopia vision. Besides, most of the multifocal lenses are mainly non-contact type. The reason is that the optical regions having different focuses can be more easily processed because the non-contact hard lenses have rigid material properties and larger area. Comparing to the soft lenses having soft material properties and smaller area, the focal lengths for each of optical regions can be precisely controlled under the lower cost situation for the non-contact hard lenses. 
     Accordingly, the dual defocus lens disclosed in the present invention can correct vision not only via reversion regulation of the diopter for slowing down the increasement of the diopter but also via imaging the retinal images in front of the retina. Thus, the retina would not deform backwards after long-time usage of the dual defocus lens disclosed in the present invention. 
     BRIEF SUMMARY OF THE INVENTION 
     The main purpose of the present invention is to provide a dual defocus lens including a central optical region and two defocus regions having different radii of curvatures. The retinal image of the central optical region is imaged within the central area of the retina. The image of the first defocus region is concentric to the retinal image of the central optical region; the image of the second defocus region is imaged in the front of the retina. Thus, the images of the defocus regions will not be imaged behind the retina and the diopter can be controlled via avoiding the deformation of the retina after a long-time usage of the dual defocus lens of the present invention. 
     Another purpose of the present invention is to provide a lens made of hydrogel or silicone hydrogel, which has a refractive-error correction part with various focuses. The refractive-error correction part includes the central optical region, the first defocus region, closely adjacent to the central optical region, and the second defocus region, positioned within the first defocus region. The corrections of the diopter for each of the regions are different. Comparing to the conventional hard lens, the lens of the present invention fits to the eyeball so that the correction of the diopter and the accuracy of the defocus are performed better. Meanwhile, the comfort and the effect of the diopter correction can be greatly improved. 
     Another purpose of the present invention is to provide a diopter correction from +0.25 D to +8.0 D progressively via the first defocus region. Hence, the correction of the diopter can be design within a range according to the demands. Unlike the conventional multifocal lens, in the present invention, the second defocus region is positioned within the first defocus region to ensure that the image can be imaged in front of the retina. The instant vertigo or short-sighted blindness caused via the rapid and frequent of relaxation and contraction of the ciliary muscle during the vision transition can be avoided. 
     Another purpose of the present invention is not only to provide better diopter correction but to reduce the production cost via improving the yield ratio for the design of the second defocus region as well. 
     For achieving the purposes mentioned above, a dual defocus lens is disclosed in the present invention. The dual defocus lens includes a refractive-error correction part, a positioning part and a periphery part. The refractive-error correction part comprises a central optical region, a first defocus region and a second defocus region, wherein the second defocus region is positioned within the area of the first defocus region and is closer to the positioning part. The first defocus region is positioned closely adjacent to the central optical region. The first defocus region, the second defocus region, the positioning part and the periphery part are all concentric to the central optical region having the same center as the refractive-error correction part. The dual defocus lens has various diopters so that the image of defocus region is imaged in front of the retina. Thus, the retina will not be elongated or deformed gradually due to the image beyond the retina and the myopia can be greatly controlled. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1A  illustrates a cross-section view of a conventional single-focal hard lens. 
         FIG. 1B  illustrates a cross-section view of a conventional multifocal hard lens. 
         FIG. 2  illustrates a top view and its corresponding cross-section view of a dual defocus lens of the present invention. 
         FIG. 3  illustrates a schematic diagram of retinal image imaged via a dual defocus lens of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments of the present invention will be further illustrated by the following associated drawings. The skilled in the art can make various changes and modifications based on the contents of the present invention. Refer to the  FIG. 2 , it illustrates a top view and its corresponding cross-section view of a dual defocus lens of the present invention. The dual defocus lens  1  includes a refractive-error correction part  11 , a positioning part  13  and a periphery part  15 . The refractive-error correction part  11  comprises a central optical region  111 , a first defocus region  112  and a second defocus region  113 . The center of the central optical region  111  is positioned in the center of the refractive-error correction part  11 . The central optical region  111 , the first defocus region  112  and the second defocus region  113  are concentrically positioned. That is, the regions  111 ,  112  and  113  of the refractive-error correction part  11  are concentric. Also, the positioning part  13  and the periphery part  15  are concentric to the central optical region  111  of the refractive-error correction part  11 . The first defocus region  112  is closely adjacent to the central optical region  111 . The second defocus region  113  is positioned entirely within the first defocus region  112  and has no contact with both the central optical region  111  and the positioning part  13 . The positioning part  13  is closely adjacent to the first defocus region  112 ; the outer edge of the positioning part  13  is directly contacted with the periphery part  15 . 
     Besides, based on the curvature of the dual defocus lens  1 , the first defocus region  112  and the central optical region  111  are concentric. The second defocus region  113 , the positioning part  13  and the periphery part  15  can be concentric or non-concentric. The reference center is the center of the refractive-error correction part  11 . 
     In order to achieve the purposes and to take the comfort as consideration, the material of the dual defocus lens  1  can be selected from hydrogel or silicone hydrogel. The specifications of the dual defocus lens  1  are illustrated as follow. The width W 1  of the central optical region  111  the refractive-error correction part  11  is ranging from 3.00 mm to 6.00 mm. The width W 2  of the first defocus region  112  is ranging from 1.00 mm to 3.00 mm. The width W 3  of the second defocus region  113  is ranging from 0.10 mm to 0.15 mm. The width W 4  of the positioning part  13  is ranging from 3.00 mm to 5.00 mm. The width W 5  of the periphery part  15  is approximately 0.50 mm. 
     Further, refer to  FIG. 2  and  FIG. 3  illustrates a schematic diagram of retinal image imaged via a dual defocus lens of the present invention. The refractive-error correction part  11  is mainly the area for correction of the diopter. The light L passing through the eyeball  2  passes through the central optical region  111  and images a retinal image on central area of the retina  21 . The image imaged via the first defocus region  112  is concentric to the retinal image imaged via the central optical region  111 . The image imaged via the first defocus region  112  is positioned on the retina  21 . Depending on characteristic of eyeball  2  and its related diopter, the position of the image imaged via the first defocus region  112  may be slightly varied. Generally, the correction of diopter of the first defocus region  112  is ranging from +0.25 D to +8.0 D. The image imaged via the second defocus region  113  is positioned behind the retina  21  instead of on the or in front of the retina  21  due to the curvature of the second defocus region  113 . Hence, the retina  21  will not be elongated or deformed after a long-time usage. In order to achieve the purposes mentioned above, within the refractive-error correction part  11 , the radius of curvature R 1  of the central optical region  111  is larger than the radius of curvature R 2  of the first defocus region  112 ; the radius of curvature R 2  of the first defocus region  112  is larger than the radius of curvature R 3  of the second defocus region  113 . As for the parts  11  and  13 , the radius of curvature R 4  of the positioning part  13  is larger than the radius of curvature R 1  of the central optical region  111 . For the refractive-error correction part  11 , the positions of the images imaged via the central optical region  111 , the first defocus region  112  and the second defocus region  113  are determined via the radii of curvatures R 1 , R 2  and R 3 . Comparing to the radii of curvatures R 1  and R 2  of the central optical region  111  and the first defocus region  112  respectively, the radius of curvature R 3  of the second defocus region  113  is apparently smaller than the radii of curvatures R 1  and R 2  so that the image imaged via the second defocus region  113  is positioned in front of the retina  21 . Basically, the ratio (R 3 /R 1 ) of the radius of curvature R 3  of the second defocus region  113  to the radius of curvature R 1  of the central optical region  111  is ranging from 0.30 to 0.80. 
     The shape of eyeball  2 , such as corneal curvature, pupil size, shape of retina and so on, the focal length and so on are all the important factors for the width design and curvature design of the dual defocus lens  1 . For instance, the radius of curvature R 1  of the central optical region  111  of the refractive-error correction part  11  is larger than 8.00 mm, the radius of curvature R 2  of the first defocus region  112  is less than 8.00 mm, and the radius of curvature R 3  of the second defocus region  113  is ranging from 3.00 mm to 8.00 mm. The distance between the second defocus region  113  and an outer edge of the central optical region  111  is ranging from 1.00 mm to 5.00 mm, and the distance between the second defocus region  113  and an outer edge of the first defocus region  112  is less than 1.50 mm. Although the second defocus region  113  is concentric to the first defocus region  112  and the central optical region  111 , the second defocus region  113  is positioned closer to the outer edge of the first defocus region  112 , that is, the second defocus region  113  is closer to the positioning part  13  and away from the central optical region  111 . It is noted that the image is mainly determined via the position of the second defocus region  113 . For instance, too much light L would be pre-focused far away from the retina  21  and the image would be blurry or out-of-focus if the second defocus region  113  is positioned too close to the central optical region  111 . Too much light L would pass through the first defocus region  112  and the image would be imaged only via a single diopter if the second defocus region  113  is positioned too far away from the central optical region  111  (too closer to the positioning part  13 ). Under this circumstance, the effect of the correction of diopter becomes poor. In order to solve this problem, the multiple defocus lens is required. However, the processes of the multiple defocus lens are complicated, low yield ratio and high production cost. Thus, the position of the second defocus region  113  must be positioned away from the central optical region  111  and be closer to the positioning part  13  surrounding the first defocus region  112 . 
     Refer to  FIG. 2 , the thicknesses of the main regions of the dual defocus lens  1  are almost identical except the outer region of the periphery part  15 . The thickness t is ranging from 0.10 mm to 0.20 mm. The distance D from the bottom to the top of the dual defocus lens  1  is approximately 3.50 mm±10%. 
     Furthermore, some more details are designed for the dual defocus lens of the present invention. Such that the slope of the central optical region and the first defocus region is smaller than a slope of the first defocus region and the positioning part. The reason for this design is that the central optical region and the first defocus region of the refractive-error correction part are mainly exerted for correction of diopter so the angle between the central optical region and the first defocus region is almost limited for fitting the eyeball smoothly and completely. In fact, a tear meniscus is exited between the refractive-error correction part and the cornea. The tear meniscus, a space filled with tears, has the function of defocus as well. However, in order to fit the lens to the eyeball smoothly and completely, the positioning part of the dual defocus lens of the present invention fits to the eyeball so that the larger slope exits between the first defocus region and the positioning part. 
     Accordingly, the dual defocus lens disclosed in the present invention provides the correction of the diopter not only via the central optical region of the refractive-error correction part but also via the first defocus region closely adjacent to the central optical region for imaging images with different focuses. Meanwhile, the second defocus region positioned within the first defocus region can shorten the focus of image so that some part of the light can be shaded. The light for imaging on the retina of the eyeball will not reach to behind the retina and the retina will not be elongated or deformed. Hence, the vision deterioration can be efficiently controlled. 
     The embodiments described above are intended only to demonstrate the technical concept and features of the present invention so as to enable a person skilled in the art to understand and implement the contents disclosed herein. It is understood that the disclosed embodiments are not to limit the scope of the present invention. Therefore, all equivalent changes or modifications based on the concept of the present invention should be encompassed by the appended claims.