Abstract:
A virtual aperture integrated into an intraocular lens is disclosed. Optical rays which intersect the virtual aperture are widely scattered across the retina causing the light to be virtually prevented from reaching detectable levels on the retina. The use of the virtual aperture helps remove monochromatic and chromatic aberrations yielding high-definition retinal images. For a given definition of acceptable vision, the depth of field is increased over a larger diameter optical zone. In addition, thinner intraocular lenses can be produced since the optical zone can have a smaller diameter. This in turn allows smaller corneal incisions and easier implantation surgery.

Description:
FIELD OF THE INVENTION 
     Cross Reference to Related Applications 
       [0001]    None 
       FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    The human eye often suffers from aberrations such as defocus and astigmatism that must be corrected to provide acceptable vision to maintain a high quality of life. Correction of these defocus and astigmatism aberrations can be accomplished using a lens. The lens can be located at the spectacle plane, at the corneal plane (a contact lens or corneal implant), or within the eye as a phakic (crystalline lens intact) or aphakic (crystalline lens removed) intraocular lens (IOL). 
         [0004]    In addition to the basic aberrations of defocus and astigmatism, the eye often has higher-order aberrations such as spherical aberration and other aberrations. Chromatic aberrations, aberrations due to varying focus with wavelength across the visible spectrum, are also present in the eye. These higher-order aberrations and chromatic aberrations negatively affect the quality of a person&#39;s vision. The negative effects of the higher-order and chromatic aberrations increase as the pupil size increases. Vision with these aberrations removed is often referred to as high definition (HD) vision. 
         [0005]    Presbyopia is the condition where the eye loses its ability to focus on objects at different distances. Aphakic eyes have presbyopia. A standard monofocal IOL implanted in an aphakic eye will restore vision at a single focal distance. To provide good vision over a range of distances, a variety of options can be applied, among them, using a monofocal IOL combined with bi-focal or progressive addition spectacles. A monovision IOL system is another option to restore near and distance vision—one eye is set at a different focal length than the fellow eye, thus providing binocular summation of the two focal points and providing blended visions. 
         [0006]    Monovision is currently the most common method of correcting presbyopia by using IOLs to correct the dominant eye for distance vision and the non-dominant eye for near vision in an attempt to achieve spectacle-free binocular vision from far to near. Additionally IOLs can be bifocal or multifocal. Most IOLs are designed to have one or more focal regions distributed within the addition range. However, using elements with a set of discrete foci is not the only possible strategy of design: the use of elements with extended depth of field (EDOF), that is, elements producing a continuous focal segment spanning the required addition, can also be considered. These methods are not entirely acceptable as stray light from the various focal regions degrade a person&#39;s vision. 
         [0007]    What is needed in the art is an improved virtual aperture IOL to overcome these limitations. 
       SUMMARY OF THE INVENTION 
       [0008]    Disclosed is a virtual aperture integrated into an intraocular lens (IOL). The construction and arrangement permit optical rays which intersect the virtual aperture and are widely scattered across the retina, causing the light to be virtually prevented from reaching detectable levels on the retina. The virtual aperture helps remove monochromatic and chromatic aberrations, yielding high-definition retinal images. For a given definition of acceptable vision, the depth of field is increased over a larger diameter optical zone IOL. 
         [0009]    An objective of the invention is to teach a method of making thinner IOLs since the optical zone can have a smaller diameter, which allows smaller corneal incisions and easier implantation surgery. 
         [0010]    Another objective of the invention is to teach a virtual aperture IOL that exhibits reduced monochromatic and chromatic aberrations, as well as an extended depth of field, while providing sufficient contrast for resolution of an image over a selected range of distances. 
         [0011]    Still another objective of the invention is to teach a virtual aperture IOL that provides a smaller central thickness compared to other equal-powered IOLs. 
         [0012]    Another objective of the invention is to teach a virtual aperture that can be realized as alternating high-power positive and negative lens profiles. 
         [0013]    Yet still another objective of the invention is to teach a virtual aperture that can be realized as high-power negative lens surfaces. 
         [0014]    Another objective of the invention is to teach a virtual aperture that can be realized as high-power negative lens surfaces in conjunction with alternating high-power positive and negative lens profiles. 
         [0015]    Yet another objective of the invention is to teach a virtual aperture that can be realized as prism profiles in conjunction with alternating high-power positive and negative lens profiles. 
         [0016]    An objective of the instant invention is to overcome these limitations by providing a phakic or aphakic IOL which simultaneously: provides correction of defocus and astigmatism, decreases higher-order and chromatic aberrations, and provides an extended depth of field to improve vision quality. 
         [0017]    Another objective of the invention is to teach a virtual aperture that can be employed in phakic or aphakic IOLs, a corneal implant, a contact lens, or used in a cornea laser surgery (LASIK, PRK, etc.) procedure to provide an extended depth of field and/or to provide high-definition vision. 
         [0018]    Another objective of the invention is to teach replacement of the virtual aperture with an actual opaque aperture and realize the same optical benefits as the virtual aperture. 
         [0019]    Other objectives and further advantages and benefits associated with this invention will be apparent to those skilled in the art from the description, examples and claims which follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  illustrates the basic method of reducing monochromatic aberrations using pupil size; 
           [0021]      FIG. 2  (A&amp;B) illustrates the basic method of reducing chromatic aberrations using pupil size; 
           [0022]      FIG. 3  (A&amp;B) illustrates the basic concept of the virtual aperture to limit the effective pupil size; 
           [0023]      FIG. 4  illustrates the virtual aperture as a high-power lens section integrated into an IOL; 
           [0024]      FIG. 5  illustrates the virtual aperture as a negative lens section; 
           [0025]      FIG. 6  (A&amp;B) illustrates the virtual aperture as a negative lens (or prism) section in conjunction to a high-power lens section; and 
           [0026]      FIG. 7  (A&amp;B) illustrates using the virtual aperture to prevent the negative effect of a small optic zone. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    Detailed embodiments of the instant invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific functional and structural details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representation basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
         [0028]      FIG. 1  illustrates a single converging lens  1  centered on an optical axis  2 . An incident ray  3  is parallel to the optical axis and will intersect the focal point  4  of the lens. If the observation plane  5  is located a further distance from the focal point, the incident ray will continue until it intersects the observation plane. If we trace all incident rays with the same ray height as incident ray  3 , we will locate a blur circle  6  on the observation plane. Other incident rays with ray height less than incident ray  3  will fall inside this blur circle  6 . One such ray is incident ray  7  which is closer to the optical axis than incident ray  3 . Incident ray  7  also intersects the focal point  4  and then the observation plane  5 . Tracing all incident rays with a ray height equal to incident ray  7  traces out blur circle  8  which is smaller than blur circle  6 . 
         [0029]    The optical principle represented here is that as the height of parallel incident rays is reduced, the corresponding blur circle is also reduced. This simple relationship is applicable to the human eye. Stated another way, for a given amount of defocus (dioptric error) in the eye, vision is improved as the height of incident rays is reduced. This principle is used when someone squints in an attempt to see an out-of-focus object more clearly. 
         [0030]    The tracing in  FIG. 1  is for a single wavelength of incident light. For polychromatic light, three wavelengths in this case, we have the situation in  FIG. 2 . It is well known for the components of the eye and typical optical materials that, as wavelength increases, the refractive index decreases. In  FIG. 2A , a converging lens  21  has optical axis  22 . An incident ray  23  consists of three wavelengths for blue (450 nm), green (550 nm), and red (650 nm) light. Due to different indices of refraction for the three wavelengths, the blue light ray  24  is refracted more than the green light ray  25 , and the green light ray is refracted more than the red light ray  26 . If the green light ray is in focus, then it will cross the observation plane  27  at the optical axis. The chromatic spread of these three rays lead to a chromatic blur circle  28  on the observation plane. In  FIG. 2B , the incident chromatic ray  29  has a lower ray height than the chromatic ray  23  in  2 A. This leads to the smaller chromatic blur circle  33  at the observation plane. Thus, just as for the monochromatic of  FIG. 1 , chromatic blur is decreased as the chromatic ray height is decreased. 
         [0031]      FIGS. 1 and 2  illustrate that decreasing ray height (decreasing the pupil diameter) decreases both monochromatic and chromatic aberrations at the retina, thus increasing the quality of vision. Another way to describe this is that the depth of field is increased as the ray height is decreased. 
         [0032]      FIG. 3A  illustrates a converging lens  34  with optical axis  2  and aperture  35 . Incident ray  36  clears the aperture and thus passes through the lens focal point  37  and intersects the observation plane  38  where it traces a small blur circle  39 . Incident ray  40  is blocked by the aperture, and thus it cannot continue to the observation plane to cause a larger blur circle  41 . An aperture which limits the incident ray height reduces the blur on the observation plane. In  FIG. 3B  we illustrate what we describe as a “virtual aperture”. That is, it is not really an aperture that blocks rays, but the optical effect is nearly the same. Rays  43  which propagate through the virtual aperture  42  are widely spread out so there is very little contribution to stray light (blurring light) at any one spot on the observation plane. This is the principal mechanism of operation of the IOL invention. 
         [0033]      FIG. 4  illustrates a basic layout of an IOL which employs the virtual aperture. In this figure, a central optical zone  46  provides correction of defocus, astigmatism, and any other correction required of the lens. Generally, for an IOL using a virtual aperture, the central optical zone diameter is smaller than a traditional IOL. This leads to a smaller central thickness which makes the IOL easier to implant and allows a smaller corneal incision during surgery. The virtual aperture  48  is positioned further in the periphery and the IOL haptic  50  is located in the far periphery. The virtual aperture is connected to the optical zone by transition region  47  and the haptic is connected to the virtual aperture by transition region  49 . The transition regions  47  and  49  are designed to ensure zero-order and first-order continuity of the surface on either side of the transition region. A common method to implement this is a polynomial function such as a cubic Bezier function. Transition methods such as these are known to those skilled in the art. 
         [0034]    In the preferred embodiment, the virtual aperture zone is a sequence of high-power positive and negative lens profiles. Thus, light rays which intersect this region are dispersed widely downstream from the IOL. These profiles could be realized as sequential conics, polynomials (such as Bezier functions), rational splines, diffractive profiles, or other similar profiles, as long as the entire region properly redirects and/or disperses the refracted rays. The preferred use is smooth high-power profiles over diffractive profiles as this simplifies manufacturing the IOL on a high-precision lathe or with molds. As known to those skilled in the art, the posterior side of the haptic should include a square edge to inhibit cell growth leading to posterior capsule opacification. 
         [0035]      FIG. 5  illustrates another profile for the virtual aperture zone  51 , namely a diverging lens profile. Note that this requires a thicker edge profile than the approach in  FIG. 4 . In  FIG. 6A  we show a close up of the preferred high-powered alternating positive and negative lens profiles with the incident and transmitted rays.  FIG. 6B  illustrates the effect of combining the profile in  6 A with either an underlying prism or negative lens. In this case not only are the emergent rays scattered widely, they are directed away from the eye&#39;s macula, or central vision section of the retina, again, at the cost of a wider lens edge. 
         [0036]      FIG. 7A  illustrates a high-power IOL  60 , usually with a relatively small optical diameter and large central thickness. When the eye&#39;s pupil is larger than the optical zone, incident rays  64  can miss the optic entirely and only intersect the haptic  61  on their way to the retina  63 . This situation would cause noticeable artifacts in the peripheral vision of the eye. Incident rays  62 , which intersect the optic zone as expected, are correctly refracted to the central vision of the retina. In  FIG. 7B  we illustrate the same optic, but now with a virtual aperture  65  between the optic and the haptic. In this case, incident rays  64  which intersect the lens outside of the optical zone, are dispersed across the retina causing no apparent artifacts. 
         [0037]    Taken together, these characteristics of an IOL which incorporates the virtual aperture can accurately be described as high definition (HD) and extended depth of field (EDOF). 
         [0038]    The basic layout of the virtual aperture IOL is illustrated in  FIG. 4 . In the preferred embodiment, the diameter of the central optical zone  46  is 3.0 mm and the width of the virtual aperture  48  is 1.5 mm. Thus, the combination of central optical zone and virtual aperture is a 6.0-mm diameter optic, which is similar to common commercially available IOLs. 
         [0039]    The central optical zone can be designed using standard IOL design concepts to provide sphere, cylinder, and axis correction, as well as higher-order correction such as spherical aberration control. These design concepts are known to those skilled in the art. 
         [0040]    The preferred virtual aperture profiles illustrated in  FIG. 4  have alternating positive and negative lens profiles with focal lengths on the order of +/−1.5 mm. These lens surface profiles can be generated using conics, polynomials (such as cubic Bezier splines), rational splines, and combinations of these and other curves. The geometry of the lens profiles is selected to adequately disperse the transmitted optical rays across the retina and at the same time be relatively easy to manufacture on a high-precision lathe or with a mold process. It is also possible to place a smooth surface on one profile (for example the front surface) and the small high-power lens profiles on the other surface profile (for example the back surface). 
         [0041]    Using the preferred virtual aperture profiles illustrated in  FIG. 4 , the edge thickness of the IOL and the center thickness of the central optical zone can be quite small, even for high-power IOLs. The material of the lens is the same as those used for other soft or hard IOL designs. 
         [0042]    The IOL design provides very good, high-definition, distance vision and the range of “clear vision” can be controlled by specification of what is meant by “clear vision” (e.g., 20/40 acuity), and the relative size of the central optic zone and the virtual aperture width. A simple equation [Smith G, Relation between spherical refractive error and visual acuity, Optometry Vis. Sci. 68, 591-8, 1991] for estimating the acuity given the pupil diameter and spherical refractive error is given in equation (1a and 1b). 
         [0000]        A=kDE   (1a)
 
         [0000]        A =√{square root over (1+( kDE ) 2 )}  (1b)
       A=acuity in minutes of arc (A=Sd/20), that is, the minimum angle of resolution   k=a constant determined from clinical studies, mean value of 0.65   D=pupil diameter in mm   E=spherical refractive error in diopters   Sd=Snellen denominator       
 
         [0048]    The second equation is postulated as being more accurate for low levels of refractive error, and gives a reasonable result. 
       For E=0, A=1 min of arc or 20/20. 
       [0049]    Solving (1b) for E yields equation (2). 
         [0000]    
       
         
           
             
               
                 
                   E 
                   = 
                   
                     
                       
                         
                           A 
                           2 
                         
                         - 
                         1 
                       
                     
                     
                       k 
                        
                       
                           
                       
                        
                       D 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    Equation (1b) tells us the acuity A given the range of depth of field (E×2) in diopters and the pupil diameter D.
 
Equation (2) tells the range of depth of field in diopters given the acuity A and the pupil diameter. D. For example, for:
 
         [0050]    Acuity of 20/40, A=40/20=2 min arc 
         [0051]    D=3.0 mm 
         [0052]    k=0.65 
         [0000]    
       
         
           
             E 
             = 
             
               
                 
                   
                     2 
                     - 
                     1 
                   
                 
                 
                   0.65 
                   × 
                   3.0 
                 
               
               = 
               0.89 
             
           
         
       
     
         [0000]    Depth of field=2E=1.8 D. Using (1b), 
         [0000]        A =√{square root over (1+(0.65×3.0×0.89) 2 )}=2
 
         [0053]    The concept of the virtual aperture can be employed in phakic or aphakic IOLs, a corneal implant, a contact lens, or used in a cornea laser surgery (LASIK, PRK, etc.) procedure to provide an extended depth of field and/or to provide high-definition vision. Also, it would be possible to replace the virtual aperture with an actual opaque aperture and realize the same optical benefits as the virtual aperture. 
         [0054]    It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein. 
         [0055]    One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.