Abstract:
A method and apparatus for correcting vision in macular degeneration patients. Following a diagnostic procedure which has been successfully tested to determine the factors needed to correct the vision of a patient with macular degeneration, the present invention describes a prototype correcting procedure and device using a computer program and display device. Through manipulation of a grid and quantitative analysis of the manipulations, the extent and correction factors needed to correct the vision of a macular degeneration patient are discussed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. Section 119(e) of U.S. Provisional Patent Application Ser. No. 61/347,445, filed on May 23, 2010, by Walter Kohn and James Klingshirn entitled “OPTICAL CORRECTION TECHNIQUES FOR MACULAR DEGENERATION”, which application is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to macular degeneration of the eye, and specifically to optical correction techniques that will assist people with macular degeneration to see more clearly. 
     2. Description of the Related Art 
       FIG. 1  illustrates a cutaway view of the eye. 
     Eye  100  is illustrated, with various parts of the eye  100  shown. Those parts that are most familiar to people are the iris  102 , pupil  104 , lens  106 , cornea  108 , and retina  110 . The iris  102 , the “colored” portion of the eye  100 , contracts and expands within an opening of the sclera  112  (the “white” part of the eye  100 ) to change the size of pupil  104 , such that light entering the eye  100  through the cornea  108  and lens  106  passes through the vitreous portion  114  and strikes the retina  110 . The choroid  116 , which lies between the retina  110  and sclera  112 , provides the vascular layer and connective tissue between the retina  110  and sclera  112 , and as the retina  110  is stimulated by incoming light transmits information from retina  110  to the brain. 
     The part of the retina  110  that is responsible for central, i.e. “sharp” vision is the macula  120 . The macula is a small, oval shaped spot on the back of the retina  110 , and is typically about 2.5 to 3 mm in diameter. Near its center is the fovea (not shown), which contains a high concentration of cone cells. Cone cells in the macula  120  detect light and retransmit it as nerve impulses to the brain via the optic nerve  118 . The cone cells in the portion of the retina  110  surrounding the fovea and macula  120  are less dense, and are responsible for the so-called peripheral, blurred vision of eye  100 . 
     The health of the eye  100  depends on many factors, and various conditions affect different portions of the eye  100  described above. One condition which is becoming more common is age-related macular degeneration (MD), which is a chronic eye condition that typically affects people age 50 and older, and is the leading cause of severe vision loss in those over 60. 
     MD affects the macula  120 , which is critical for acute vision, reading, and recognizing faces. MD can occur in people of any age, but usually affects older people. Because of lengthening average life-expectancy, MD has become increasingly common, and thus, the study and treatment of MD has become increasingly more important. 
     In a person with MD, the macula  120  begins to deteriorate in various ways. In particular, distorted central vision occurs in or near the center of the visual field. MD is associated with photoreceptor damage and a roughened macula  120 , often caused by the presence of fluid or blood in the subretinal space. This roughening results in distortion of the patient&#39;s central field of vision. There are two types of MD, “dry MD” and “wet MD.” Symptoms usually develop gradually and painlessly, and vary depending on the form. Most cases of MD start as the dry type, which also is the most common type. In 15 percent of cases, the disease advances to the wet type, often causing rapid vision loss. 
     The current approach to treatment of both types of MD vary depending on the patient and the type of MD. Treatments typically include injectable drug therapy, photodynamic therapy, laser treatment, surgery, and vitamin and mineral supplements to slow the advance of the disease. Research is focused on slowing or stopping the progression of the disease. 
     Thus there is a need in the art for devices that can improve the vision of MD patients. It can also be seen, then, that there is a need in the art for methods, apparatuses, and devices to help those with MD regardless of the current state of a given patient&#39;s vision. 
     SUMMARY OF THE INVENTION 
     To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses various techniques and devices to correct or partially correct the vision of a MD patient. 
     A method for quantitatively and non-invasively characterizing a patient&#39;s MD is disclosed and the results are used to provide a cost effective corrective device for the patient. The corrective device can be a computer screen, a camera and a mobile computer, a pair of appropriate MD eyeglasses or contact lenses, or a custom made glass slab which incorporate the correction factors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
         FIG. 1  is a cutaway view of the eye; 
         FIG. 2  illustrates an Amsler Grid; 
         FIG. 3  illustrates an Amsler Grid as seen by a patient with macular degeneration; 
         FIG. 4A  illustrates an Amsler Grid used for quantitative assessment and feedback from the patient in accordance with one or more embodiments of the present invention; 
         FIG. 4B  shows an example of undistorted reading material being displayed on a computer screen as seen by an MD patient; 
         FIG. 4C  illustrates an arbitrary function illustrated in one dimension analyzed with an embodiment of an interpolation function of the present invention; 
         FIG. 5  illustrates the definition of the displacement vector d mn  shown with a coordinate system defined in the perspective of a person with normal vision. The vector d mn  is formed by displacing a grid intersection point from its initial postion r mn  to its final postion r′ mn ; 
         FIGS. 6A-6B  illustrates an arbitrary vector field remapping having both gradient and curl components, and an interpolation of this field to a larger array, in accordance with one or more embodiments of the present invention; 
         FIGS. 6C and 6D  illustrate a computer-based compensation method in accordance with one or more embodiments of the present invention; 
         FIGS. 6E-6G  illustrate a dynamic compensation scheme in accordance with one or more embodiments of the present invention; 
         FIGS. 6H and 6I  illustrate additional embodiments of computer-based compensation devices in accordance with one or more embodiments of the present invention; 
         FIGS. 7A-7B  illustrate an optical correction device in accordance with one or more embodiments of the present invention; 
         FIG. 8  illustrates a process chart in accordance with one or more embodiments of the present invention; and 
         FIGS. 9A-9F  illustrate a timeline of perceptions by a patient and a technician in accordance with one or more embodiments of the present invention. 
         FIG. 10  illustrates the virtual displacement (lateral and/or vertical) of a luminous point on a horizontal plane by viewing it through a glass triangle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     Overview 
     The present invention describes methods and apparatuses for quantitatively characterizing the distorted vision of a MD patient, and for providing methods and apparatuses for quantitatively correcting that distorted vision. 
     Amsler Grid 
       FIG. 2  shows an Amsler Grid. 
     Amsler Grid  200  is a square grid of horizontal lines  202  and vertical lines  204 , with a central spot  206 , that has been used to characterize the health of a person&#39;s central visual field. Typically, the grid  200  is used merely to detect and monitor distortions in the visual field and how these distortions may change over time. Amsler Grid  200  is typically a square grid, typically 10 cm×10 cm divided into 20×20=400 squares. 
     When viewed by a person with healthy central vision, the grid appears to be “undistorted,” e.g., each area defined by horizontal lines  202  and vertical lines  204  appears to be the same, with angles at 90 degrees throughout grid  200 , and no dark spots or changes in contrast are registered by the viewer. 
       FIG. 3  illustrates an Amsler Grid as seen by a patient with MD. 
     When a patient with MD views grid  200 , one or more of the horizontal lines  202  and/or vertical lines  204  appear “distorted,” e.g., that the horizontal line  202  or vertical line  204  does not appear straight, does not appear to cross other lines at 90 degrees, and the area defined by lines  202  and  204 , is not uniform throughout the grid. As such, area  300 , defined by the circle on grid  200 , will look distorted to a given patient. Area  300  can take any shape, and can appear anywhere on grid  200 ; each patient will perceive the grid differently and record those perceptions differently. 
     Since a healthy macula  120  is typically very flat and smooth, any distortions in area  300  and dark spot(s)  302  are called “roughening” of the macula  120  surface, e.g., due to bursting of small blood vessels or new blood vessels growing underneath the macula. 
     To date, the Amsler Grid  200  has been used primarily as a non-quantitative tool to characterize vision. The patient is asked to view the grid, and to describe any perceived distortions. For example, the patient might have been asked if the grid is more distorted than it appeared at the previous check-up. The present invention uses a specialized Amsler Grid as a quantitative tool which is essential for the creation of a correcting device. 
     To clarify the general principles which apply to all implementations, we begin with a scenario in which a new patient whose macular degeneration has been quantitatively diagnosed, as previously discussed, is seated nest to a technician. They are both in front of a monitor which shows an Amsler grid and textual or other visual material. Before the patient developed macular degeneration they both would have seen all the presented material clearly and correctly, see  FIGS. 9A and 9B . With the patient&#39;s added MD and before correction, he sees this material distorted, see  FIG. 9C , while, of course, the technician&#39;s vision remains unaffected, see  FIG. 9D . When one of the possible corrections is applied to the presented material, the latter is distorted in a compensatory way so that the patients perception is back to normal as shown in  FIG. 9E  while the technician sees the presented material as distorted by the action of the device as shown in  FIG. 9F . Finally, the patient, with now normal vision can walk away with the device, as can the technician without the device. 
     Quantitative Assessment and Feedback 
       FIG. 4A  illustrates an Amsler Grid used for quantitative assessment and feedback in accordance with one or more embodiments of the present invention. 
     Computer  400 , with monitor  402  and input control device  404 , are shown. Computer  400  can be any type of computing device, e.g., a Personal Computer (PC), Macintosh (Mac) computer, or a touch-screen device such as an iPad or touch-screen netbook, without departing from the scope of the present invention. Further, computer  400  can be coupled to a network  406 , either via wires or a wireless connection, to allow for additional processing on the inputs and outputs or delivery of new inputs and/or outputs if desired. Such computing platforms are well known in the art, and the specifics of each of the computers  400  are contemplated within the scope of the present invention, e.g., if the computer  400  is a touch screen, then input device  404  would be the screen of monitor  402  rather than a separate keyboard, mouse, or other device, etc. 
     As shown in  FIG. 4A , a specialized Amsler Grid  408  is shown on monitor  402 . Specialized Amsler Grid  408  is programmed into computer  400 , or is accessible to computer  400  via network  406 . Specialized Amsler Grid  408  has a central point  410 , a plurality of horizontal lines  412   a - 410   s  and a plurality of vertical lines  414   a - 414   s , similar to the Amsler Grid  200  shown in  FIG. 2 . However, Specialized Amsler Grid  408  of the present invention allows a user (patient) to move the horizontal lines  412   a - 412   s  and vertical lines  414   a - 414   s  in a particular way to quantify the distortion seen by the user (patient). 
     The present invention allows the patient to move each line, e.g., horizontal line  412   j  which can be highlighted for the patient&#39;s ease of detection, in specific ways to transform the “distorted” grid that the patient sees into a “normal” grid such as would be perceived by a patient without MD. 
     Diagnostic Test—Grid Transformation 
     Using input control device  404 , the present invention allows the patient to move the intersection points of the horizontal lines  412   a - 412   s  and  414   a - 414   s  of specialized Amsler Grid  408  in such a way that, when completed, the edited grid looks to the patient like a perfect Amsler grid. 
     Initially, specialized Amsler Grid  408  is set up such that it looks to the technician like a “normal” Amsler Grid (e.g. Amsler Grid  200 ). The patient, usually seated with a technician, focuses his vision and attention on center spot  410 , and moves the intersections of the lines  412 - 414  until the modified specialized Amsler Grid  408  appears to the patient to be a “normal” Amsler Grid. 
     In one embodiment of the present invention, the patient is seated next to a technician and viewing the same monitor  404 . The patient&#39;s chin is placed at a fixed distance from monitor  404 , typically in a chin rest, to keep the patient&#39;s eyes at a fixed viewing distance from monitor  404 . 
     The monitor displays a specialized Amsler grid  408 . The ratio of the Amsler grid  408  width and height to the viewing distance is typically 1:4, but can have other values without departing from the scope of the present invention. For example, and not by way of limitation, if the Amsler grid  408  displayed on the monitor is 10×10 cm, then the viewing distance would typically be 40 cm. 
     Detailed Technical Description 
     The procedure of the present invention is typically repeated twice, once for each eye, but can be repeated as many times as desired or only performed once if desired. The eye that is not being tested is typically covered or otherwise blocked. 
     At the beginning of the diagnostic procedure, the patient perceives the grid as distorted, while the technician perceives it as undistorted. During the diagnostic procedure, the patient uses the computer mouse to move the intersection points of the Amsler Grid  408  in such a way that when completed, he perceives the edited Amsler Grid  408  as undistorted. 
     During the editing procedure the computer  400  records the displacement vectors D mn , of all intersection points of the Amsler Grid  408 . These displacements are stored in the computer  400  as a set of displacement vectors:
 
 D   mn   ={u ( x   mn   ,y   mn ), v ( x   mn   ,y   mn )}.
 
 m,n=− 10 to 0 to +10 (or 0-20)
 
     These displacements constitute the diagnosis of the patient&#39;s spatial MD distortions. 
     During the editing procedure, the computer  400  presents the specialized Amsler Grid  408  with most of the lines  412 - 414  in a lighter shade, e.g., grey, and either automatically highlights one of the lines, e.g., line  412   j  as shown in  FIG. 4A , or allows the patient to manually select any of the lines  412 - 414  to edit. 
     Once a grid line  412 - 414  is selected, e.g., grid line  412   j , the endpoints of the selected line  412   j  and/or line  412   j  itself is highlighted, e.g., the color of the line  412   j  is changed to a different color than the remainder of the lines in grid  408 , or the contrast of line  412   j  is changed with respect to the remainder of the lines in grid  408 , such that it is easy for the patient to detect the selected line  412   j.    
     The patient then places a cursor  416  on the selected line  412   j , which is constrained by computer to “snap” to the intersection points between the selected line  412   j  and the other lines (in this case, lines  414   a - 414   s ) in grid  408 . The intersection point that is selected by the placement of cursor  416 , which is being controlled by input control device  404 , is also typically “highlighted” for the user to make it easier for the user to determine when selected line  412   j  has been moved to the proper correction point. Again, this is shown by point  418 , which can be shown in a different color or other visual indicator to show the patient which point  418  of the selected line  412   j  is being moved with input control device  404 . 
     The highlighted intersection point can be manually moved by the patient, by dragging it with input control device  404  until it is in the correct position, or the highlighted intersection point can be automatically moved by the computer, while the patient uses input control device  404  to indicate whether the new position is better or worse than the previous position. The order in which the grid lines are selected, and the order in which the line intersection points are selected can be manually chosen by the patient, or the computer can automatically guide the patient through a preset ordering of lines and intersection points. So for example, and not by way of limitation, the computer  400  can start the patient on line  412   a , and move the point  418  from the intersection of lines  412   a  and  414   a  to the intersection of lines  412   a  and  414   b  upon an input from the patient, can allow the patient to randomly select which line  412 - 414  to start with and where to place point  418 , or any combination thereof. 
     To the technician, prior to the start of the manipulation of grid  408 , grid  408  will appear undistorted, while, to the patient, the grid will appear distorted. While fixing the gaze on the center point  410 , which also may be highlighted or otherwise rendered on monitor  404  to assist the patient in maintaining focus at this point  410 , the patient either systematically, randomly, or with assistance from the computer, edits one grid line  412   a - 412   s  and  414   a - 414   s  at a time. 
     The endpoints of each line are typically maintained at a fixed position on the grid  408 , whereas the intersection points of grid lines  412   a - 412   s  and  414   a - 414   s  are manipulated by the patient. The endpoints of grid lines  412   a - 412   s  and  414   a - 414   s  can be maintained at fixed positions with respect to Amsler Grid  200  because the periphery of the grid  408  is close to the boundary between central and peripheral vision, and is known to be very weakly distorted in an AMD patient. Therefore visual cues for keeping the eye centered, and for helping to straighten the interior of the grid typically reside at the periphery and at the center of grid  408 . Since peripheral vision is typically not color sensitive and has low resolution, peripheral cues, such as the endpoints of grid lines  412   a - 412   s  and  414   a - 414   s , and center point  410 , are typically to be large with high contrast. 
     Grid Editing Procedure 
     Typically, the patient works from the outside into the center, editing one grid line  412   a - 412   s  and  414   a - 414   s  at a time. The selected grid line  412   a - 412   s  and  414   a - 414   s  is highlighted, while all other grid lines  412   a - 412   s  and  414   a - 414   s  are dimmed. 
     After a grid line  412   a - 412   s  or  414   a - 414   s  has been selected, the patient uses the input control device  404 , e.g., computer mouse, touch screen, and/or arrow keys to move the intersection points  418  of the grid  408 . A grid intersection is typically selected by clicking on the point  418  with a mouse; when selected, it is highlighted, dragged with the mouse, and clicked again to fix the point, or some other indication is made by the patient that the dot is in a “correct” position as viewed by the patient. 
     Internally the computer  400  uses a coordinate system that makes grid  408  look horizontal and vertical to the technician. When the patient edits a vertical line  412   a - 412   s , the grid  408  intersection of the selected line  412   a - 412   s  is constrained by the computer  400  so that the intersection can only be moved to the left and right in the computer&#39;s coordinate system. Because of his macular degeneration the patient will in general perceive this movement as not exactly vertical. 
     In the first phase, the patient will straighten out all of the vertical lines  412   a - 412   s  as well as can be performed given time and peripheral vision of the patient. When this phase is completed, all of the vertical lines  412   a - 412   s  will look perfectly straight to the patient and pass through the appropriate boundary points at the periphery of grid  408 . In the second phase, without regard to the vertical lines, the patient similarly straightens out all horizontal lines  414   a - 414   s . Computer  400 , similarly, constrains movement of the intersections of horizontal lines  414   a - 414   s  to move only up and down in the computer&#39;s coordinate system. However, because of the macular degeneration, this second phase alignment by the patient slightly disturbs the alignment of the vertical lines. Therefore the entire process may need to be iterated one or more times. 
     The distortion seen by the patient at the beginning of the procedure, and the distortion seen by the technician at the end of the procedure are called complementary. The distortion seen by the technician at the end will have the same magnitude but will have the opposite sign, e.g., movement seen by the patient in a positive x-direction will be seen by the technician as a movement in the negative x-direction. 
     Two Dimensional Discretized Displacement Vectors 
     The coordinates of the undistorted Amsler grid intersections are denoted by 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 r mn  = (x m, n , y m, n ) 
                 m, n = 0, 1, 2 . . . N 
                 N = 20 
               
               
                   
                   
               
             
          
         
       
     
     The 21×21 displacement vectors defined at all the points on the Amsler grid  408 , which are necessary to remove the distortions of the grid  408  perceived by the patient, are denoted as
 
 d   mn =( u   mn   ,v   mn )
 
     These displacement vectors represent the quantitative diagnosis of the geometry of each patient&#39;s macular degeneration. 
     u mn , v mn  Displacement Vector Components 
     All grid coordinates are defined in cartesian coordinates from the perspective of a normal viewer. Since the edges of the Amsler Grid  408  are constrained as fixed with respect to a “normal” Amsler Grid  200 , these components vanish on the edges of the Amsler grid  408 . 
     The intersection points of the distorted grid are denoted by r′ mn . They are characterized by the original grid coordinate positions plus the displacement vectors:
 
 r′   mn   =r   mn   +d   mn  
 
     The movement of individual grid  408  intersections and the use in determining the correction factors are discussed with respect to  FIG. 5 . 
     The two dimensional set of vectors associated with the N 2  displacement intersections constitute the patient&#39;s diagnosis d mn . The displacement vectors d nm  are used to compute the distorted image that looks to the patient like a perfect image. A high resolution version of the a digital distortion field, when applied to the page of a book, will be easier for the patient to read, as discussed with respect to  FIG. 4B . 
     Displacement Vector Field Interpolation 
     The displacement vector field that is defined by the quantitative diagnosis has about 400 vectors with the resolution of 20×20 cells within the Amsler grid  408 . For practical applications, higher resolution may be required. A typical digital image has a resolution of several million pixels. For example, a moderately priced digital camera has resolution of 3648×2736 pixels, for a total resolution of approximately 10 million pixels. A two-dimensional interpolation scheme is used to increase the resolution of the displacement vector field from the original 20×20 resolution, to a resolution that matches the image that is being distorted. The patient obviously cannot move 10 million individual pixels into new positions, and thus interpolation must be employed. 
     Sine Transform for Two-Dimensional Interpolation 
     The two-dimensional displacement vectors associated with the N 2  intersections of the Amsler Grid  408  express the diagnosis, and the present invention utilizes an interpolation schema to increase the resolution of the diagnosis. Although described with respect to a particular interpolation method herein, other methods of interpolation are possible within the scope of the present invention. 
       FIG. 4C  illustrates an arbitrary function illustrated in one dimension analyzed with an embodiment of an interpolation function of the present invention. 
     Function  454 , also referred to as arbitrary function d m , is drawn as a function of variable x. The values of d m  at each grid  408  position x m  are known, and are designated d(x m ). The interpolation functions create a function that passes exactly through each point d(x m ) and provides an expression d(x) for arbitrary values of x. 
     Equation  455  which is the expression for d(x m ), is a summation of N sine functions with successively decreasing wavelength. The first term in the series, sin(1π/L) has a half wavelength of L, where L is the length of the side of the grid  408 . The second term has a full wavelength across the grid  408  width, etc., and the final component has a component sin (20π/L) which has a half wavelength within a single square in grid  408 . 
     The A α  terms are the amplitudes of the individual sine functions for each of the sine components within the series. Equation  456  which is the Fourier inversion of equation  455  gives an expression for finding the A α  terms. Equation  457 , the interpolation function, uses the A α  amplitudes to provide an expression d(x) for arbitrary values of x. 
     The straightforward generalization of the above one dimensional equations into two dimensions results in equations  458  and  459 . Equation  458  gives a function that can be evaluated to find the displacement value d(x,y) for arbitrary values of x and y. Equation  459  is the inverse Fourier transformation of equation  458 , which provides the amplitude coefficients A αβ . 
     Thus, the resolution of grid  408  defines the minimum size of a visual defect that the present invention can correct; for example, and not by way of limitation, if the grid  408  square is 0.5 cm on a side, then the highest resolution sine function will have a wavelength of 0.5 cm. However, by using different grid  408  sizes, or, for example, having the grid  408  have a smaller resolution in specific areas, smaller defects can be corrected for using the present invention. So, for example, grid  408  can have smaller grid sizes in the center (where the center of the visual field has a much higher resolution and therefore needs more exact correction), and larger squares at the periphery of grid  408 . 
     Displacement of Amsler Grid Lines 
       FIG. 5  illustrates a displacement of specialized Amsler Grid lines in accordance with one or more embodiments of the present invention. 
     Grid  500  shows a “normal” Amsler grid with lines  412   j  and  414   m  that are unmodified and viewed as linear and perpendicular by computer  400  and a healthy eye, and lines  512   j  and  512   m  after being edited by a patient with AMD to correct for his perceived distortion. 
     In the standard coordinate system, point  502  is where lines  412   j  and  414   m  intersect. However, as described herein, the patient has moved these intersection points, and, in the example shown in  FIG. 5 , has moved this to point  502 . Computer  400  can now compute the magnitude change in both horizontal and vertical directions for point  502  now moved to point  504 , as well as for all other intersection points for each of the lines  412  and  414  (now moved to lines  512  and  514 ) in grid  408 . By remapping the grid  408  into this new coordinate space, monitor  402  now has correction factors based on the displacement vectors  503  to apply to a given image displayed on the monitor  402  to allow the image to appear “normal” to the patient (and to be distorted to a viewer with healthy vision).  FIG. 6A  illustrates an example vector field  600 , showing such a mapping of grid  408 , and  FIG. 6B  illustrates a 100×100 interpolated displacement vector field  602  generated by interpolating the diagnostic results shown in  FIG. 6A . 
     Computer Corrective Optics 
     The present invention corrects the distorted vision caused by MD by applying a compensating distortion to the material displayed on a computer screen.  FIG. 4B  shows an example of undistorted reading material (text  450 ) being displayed on a computer screen as seen by the MD patient. The distortions perceived within the circle  456  by the MD patient can be corrected by applying the compensating distortion which improves the patient&#39;s reading ability. 
     Normally as a person reads, his eye scans the page from left to right. For the MD patient, the compensatory distortion needs to be centered at the center of the patient&#39;s field of view. This implies that the compensating distortion should move from left to right as the eye scans from left to right. The present invention has a mode where the distortion field repeatedly sweeps across the reading material following the text, from left to right, starting at the top of the page, and moving downward, at a speed controlled by the patient. The patient keeps his eyes fixed on the center of the distortion field as it sweeps, aided for example by a cross-hair indicator. 
     Another embodiment of the present invention keeps the distortion field centered on the reading material. The reading material is streamed through the distortion field at a speed controlled by the patient. 
     Each of the patient&#39;s eyes will require its own compensating distortion field. The patient might cover one eye, and read with the better eye. Alternatively, a stereo vision approach could be employed. 
     After completion of the diagnostic procedure, and with the aid of interpolation, the perceived spatial distortions can be corrected by application of compensating distortions. When the patient views an object using the compensation method, his perceived macular distortions will be eliminated (or at least substantially corrected). 
     Compensating for Distortion by Computer 
       FIGS. 6C and 6D  illustrate a computer-based compensation method in accordance with one or more embodiments of the present invention. 
     In a computer  400  based compensation method, reading material can be scanned, photographed, or otherwise converted into an array of pixels. It appears distorted to the patient, as shown in image  604  of  FIG. 6C . Computer  400  software corrects the distortions by displacing each pixel using displacements obtained from the diagnostic procedure described herein. When viewed at the appropriate distance, the text now appears undistorted as shown in image  606  of  FIG. 6D . 
     Dynamic Compensation 
       FIGS. 6E-6G  illustrate a dynamic compensation scheme in accordance with one or more embodiments of the present invention. 
     Patients need to read entire pages, not just the small circles such as in  FIG. 4   b . The solution is to apply the compensation dynamically.  FIG. 6E  shows an example of a computer-based dynamic compensation method, where text  611  flows through the distortion field (shown highlighted as area  612 ) in a ticker-tape manner. The patient typically fixes his or her gaze at a fixed dot in the center of the area  612 . The computer  400  then applies the compensating (anti-distortion) displacement field to the text or image within the area  612 , so that it appears undistorted to the patient. 
       FIG. 6F  shows that the text  611  has been moved to the left (the area  612  has moved to the right) in image  614 . Of course, area  612  can be moved in any direction without departing from the scope of the present invention.  FIG. 6G  shows in image  616  that the text has moved further to the left, i.e., area  612  has moved farther to the left, to allow the patient to properly view the text in a flowing manner. Area  612  can move at varying speeds based on user inputs or automatic inputs to computer  400  without departing from the scope of the present invention. 
     Additional Embodiments of Computer-Based Correction Implementations 
       FIG. 6H  illustrates a handheld computer  614 , e.g., cellular telephone, PDA, digital camera, etc., with a built in video camera and screen. The AMD patient scans the device  614  over the reading material. The compensating distortion is applied to the video image in real time. 
       FIG. 6I  illustrates existing glasses  616  for watching videos. Glasses  616  can be adapted for an AMD patient by adding a composite device comprising a small computer and video camera. The computer would apply the anti-distortion compensation to the video stream. The video glasses would then display the corrected result. A picture-in-picture technique can be employed to simultaneously display the corrected and uncorrected front view if desired. 
     Non-Computer Corrective Optics 
     Glass—Plastic—and Other Corrective Optics 
     It is well known that spectacles or contact lenses correct nearsightedness, farsightedness and astigmatism. The present invention employs a similar approach to solve a geometrically more challenging problem. 
     The present invention explains the general scheme of correcting for MD caused visual distortion, and discusses two broad approaches: One—computer based without glass or glasslike components; the other, based on refractive materials, typically glass and/or plastic, or based on deformable reflective materials, typically metal or plastic. Needless to say, these particular choices are not necessarily exhaustive. 
     The distorted vision created by MD is quantitatively characterized as a 2D discrete vector field d mn . The present invention corrects the distortion caused by MD by appropriately modifying the top surface of a plate of optical glass. The modified surface causes light rays to be appropriately refracted as they travel from the reading material or other object viewed by an MD patient, through the glass, to the patient&#39;s eye. The glass is machined or otherwise processed such that the modified surface causes an apparent displacement of the reading material or other viewed object. The corrugation is typically smooth and compensates for the spatial distortion caused by the MD. 
     Using the results of the present invention, an arbitrary, smooth macular distortion can be corrected by a suitably patterned slab of optical material. 
     A refractive optical device, machined from glass or optical grade plastic, is designed using the compensating distortions on the surface of the device so that the surface contours and spatially varying thicknesses of the device cancel the distortions caused by the patient&#39;s Macular Degeneration. 
       FIG. 10  illustrates the correction of MD by Optical Refraction. A standard Amsler grid is placed on a flat surface and viewed from above. We represent the Amsler grid by a collection of closely spaced luminous points lying on the regular grid points. An MD patient will perceive the pattern of the Amsler grid points as distorted. Each point needs to be laterally moved so as to create a perfect grid. This can be accomplished by viewing the Amsler grid (one eye at a time) from a height of about 40 cm through a 10 cm by 10 cm slab of transparent material (glass, plastic) where the top surface z=z(x,y) is patterned so as to eliminate the macular distortions. This is illustrated in  FIG. 10 , where a single luminous point P is laterally displaced to a virtual point P′. For clarity,  FIG. 10  illustrates the virtual displacement of point P using a refractive triangle. This can be generalized to the geometry of an arbitrary refractive surface, by rotating and displacing the triangle in such a way that at each ray/surface intersection point, its slope matches the instantaneous slope of the arbitrary surface. In  FIG. 10 , a light ray, r is drawn from the luminous point P to the eye. The ray is bent by refraction at the surface of the triangle, creating ray r′. A second ray r p  from luminous point P, perpendicular to the triangle surface is chosen. The virtual point P′ exists at the intersection point of r′ and r p . 
     Another method of using a refracting optical device for correcting macular distortion would take the form of specially designed contact lenses. Each lens would be designed with spatially varying thickness custom made to cancel the macular distortions. Existing methods for astigmatic patients can be employed to maintain the proper orientation of each lens. 
     Schematic Views of Corrective Devices 
       FIGS. 7A-7B  illustrate an optical correction device in accordance with one or more embodiments of the present invention. 
       FIG. 7A  illustrates schematic  700 , showing eye  702  viewing sailboat  704 . Device  706  is placed between eye  702  and sailboat  704 , such that light  708  reflected by or emitted from sailboat  704  is viewed through device  706  by eye  702 . 
     A person with MD looking at sailboat  704  without device  706  of the present invention would see distorted image  710 . When a correcting device  706  of the present invention is interposed, the distortion is eliminated, and the person would see a distortion corrected image  712 . 
       FIG. 7B  illustrates a perspective view of a device in accordance with one or more embodiments of the present invention.  FIG. 7B  illustrates a slab made from glass or optical quality plastic, with dimensions such as 10×10×2 cm. The pattern on the top surface and the plate thickness are custom made so as to cancel the distortions created by the individual patient&#39;s macular degeneration. 
     Device  706 , as shown in  FIG. 7B , has been modified to include correcting surface  732 , which has been determined for a given patient as described herein. To create correcting surface  732 , device  706  can be machined and/or polished from top  730  down, which would reduce height  720  to a new height, or built from bottom  729  up. Although shown as a random surface, correcting surface  732  can take any shape as required by the present invention to eliminate or reduce the distortion. 
     Correcting surface  732  might also be formed in other ways, e.g., through the buildup of films or various materials on one or more surfaces of device  706 . Various films, with different indices of refraction, or various materials, whether heterogeneous or homogeneous, can be used to create device  706  within the scope of the present invention. 
     Correcting surface  732  can be combined with other visual corrections, e.g., those found in typical eyeglasses, in that top  730  and/or other surfaces of device  706  can be curved or otherwise shaped to correct for astigmatism, nearsightedness, farsightedness, magnification, etc. Further, device  706  can be combined with the computer-based solution described within the scope of the present invention. 
     Device  706  can be employed in several embodiments within the scope of the present invention; for example, and not by way of limitation, device  706  can be used over the lens of a digital camera, such that the digital camera displays the image through device  706  to a user. Further, device  706  can be integrated into a pair of eyeglasses, which the present invention refers to as “Macular Degeneration (MD) spectacles,” or used as contact lenses. Correcting surface  732  can further be placed on either or both sides of device  706 , e.g., opposite top  730 , such that ophthalmic devices  706  would allow for fitting to the eye or better corrective action produced by device  706 . 
     Process Chart 
       FIG. 8  illustrates a process chart in accordance with one or more embodiments of the present invention. 
     Box  800  illustrates preparing, on a computer, a standardized Amsler grid having a plurality of horizontal lines and a plurality of vertical lines. 
     Box  802  illustrates manipulating, using an input device to the computer, at least one intersection of the plurality of horizontal lines and the plurality of vertical lines. 
     Box  804  illustrates computing a difference between an original position of the at least one intersection and the manipulated position of the at least one intersection. 
     Box  806  illustrates applying the difference to an incoming image to correct a perception of the image. 
     CONCLUSION 
     This concludes the description of one or more preferred embodiments of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.