Abstract:
Over the years, eyestrain and headaches have become an increasing problem for computer users, especially those who require eyeglasses. To combat this problem, lenses and a method/system for calculating the characteristics of these lenses have been developed. The method/system takes age, height, and the user&#39;s or wearer&#39;s prescription into account to help optometrists grind lenses that are specifically adapted for use with computers. Therefore, it is now possible to have an automated system that determines characteristics for lenses that are adapted for use with computers.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates generally to determining eyeglass lens characteristics and, more particularly, to a method of determining characteristics for lenses adapted for use with computers. 
       BACKGROUND 
       [0002]    Eyeglasses have been a medical fixture for centuries. As a result of many years of research, two basic lenses are employed: spherical lenses and cylindrical lenses. A spherical lens has the same general uniform curvature over the surface of the lenses whereas the cylindrical lens has a uniform curve relative to an axis. Each of these two lenses is further defined by type as being positive (convex) and negative (concave). The power of such lenses is varied by changing the curvature and shape of the lenses and is measured in diopters, where one diopter is a focal length of one meter. Determining such characteristics for eyeglass lenses is very precise, and this total power/curvature (prescription) is defined by the following equation: 
         [0000]        OD/OS=A±B×C plus±D.   (1) 
         [0000]    OD (right eye) and OS (left eye) designate to total lens strength. “A” is the spherical base curve and type (positive or negative). “×B×C” denotes the cylindrical strength, type, and axis orientation, and “plus±D” indicates bifocal segment strength. Lenses, though, have been specifically refined for “everyday use.” 
         [0003]    Increasingly, however, eye strain and headaches have been a frequent problem for many people who use a computer monitor for long periods of time, especially for people who wear eyeglasses. As a result, glasses for use with computers have been developed and sold, but determining the correct optical characteristics for them has been the result of trial and error or guesswork. Some prior-art examples of methods and systems for providing or determining lens characteristics are U.S. Pat. Nos. 5,204,702, 5,661,539, 6,345,893, 6,592,223, 6,709,101, and 6,726,327 and U.S. patent Publication Nos. 2003/0218721, 2005/0122472, 2005/0231683, and 2005/0270482. None of these reference discloses an automated method or system for calculating characteristics for lenses adapted for use with a computer. 
         [0004]    Therefore, there is a need for a method and/or system that automatically determines the characteristics of lenses adapted for use with computers. 
       SUMMARY 
       [0005]    A preferred embodiment of the present invention, accordingly, provides a method and system for determining characteristics for lenses adapted for use with computers. A plurality of physical characteristics of a human user are input into the system, where the physical characteristics at least include a distance prescription and a work distance. A corrected age and a height factor are each calculated from at least one of the physical characteristics, and a computer work distance prescription is calculated. The computer work distance prescription is a function of a ratio of the corrected age and work distance the distance prescription, and the height factor. 
         [0006]    In accordance with a preferred embodiment of the present invention, the calculation of the corrected age further comprises determining an age of the user and assigning a value. If the user&#39;s age is less than 30, then the corrected age is 30. If the user&#39;s age is between 30 and 60, the corrected age is the user&#39;s age. Finally, if the user&#39;s age is greater than or equal to 60 the corrected age is 60. 
         [0007]    In accordance with a preferred embodiment of the present invention, the calculation of the height factor further comprises determining a height of the user and assigning a value. If the user&#39;s height is greater than or equal to 75 inches, the height factor is zero, and if the user&#39;s height is less than or equal to 75 inches, the height factor is calculated as a function of the user&#39;s height. 
         [0008]    In accordance with a preferred embodiment of the present invention, the calculation of the computer work distance prescription further comprises summing the ratio of the corrected age and work distance, the distance prescription, and the height factor. 
         [0009]    In accordance with a preferred embodiment of the present invention, a work distance and a distance prescription for the user are established. 
         [0010]    In accordance with a preferred embodiment of the present invention, the calculation of the computer work distance prescription further comprises calculating the lens power by summing one percent of the ratio of the corrected age and work distance with the height factor and the distance prescription. 
         [0011]    A preferred embodiment of the present invention, accordingly, also provides a lens for a human user adapted for use with computers comprising a refractive material having a first side and an opposite second side. Each of the first and second sides has a topology and an arcuate profile, and the topologies and arcuate profiles of the first and the second sides are functions of a ratio of a corrected age and a work distance of the user, a distance prescription of the user, and a height factor of the user. 
         [0012]    In accordance with a preferred embodiment of the present invention, the lens is tinted blue, yellow, rose, or lavender. 
         [0013]    In accordance with a preferred embodiment of the present invention, the corrected age is 30 (if a user&#39;s age is less than 30), the user&#39;s age (if the user&#39;s age is greater than 30 but less than 60), or 60 (if the user&#39;s age is greater than or equal to 60). 
         [0014]    In accordance with a preferred embodiment of the present invention, the height factor is 0 (if the user&#39;s height is greater than or equal to 75 inches) or a function of the user&#39;s height for all heights less than 75 inches. 
         [0015]    In accordance with a preferred embodiment of the present invention, the topologies and arcuate profiles of the first and the second sides are a sum of the ratio of the corrected age and work distance, the distance prescription, and the height factor. 
         [0016]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0018]      FIG. 1A  is a cross-sectional view of a lens adapted for use with eyeglasses worn by a computer user in accordance with a preferred embodiment of the present invention; 
           [0019]      FIG. 1B  is a front elevation view of the lens of  FIG. 1A ; and 
           [0020]      FIGS. 2A and 2B  are flow charts depicting the method for calculating the characteristics of lenses adapted for use with computers of  FIGS. 1A and 1B . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    In the discussion of the Figures the same reference numerals will be used throughout to refer to the same or similar components. 
         [0022]    Referring to  FIGS. 1A and 1B  of the drawings, the reference numeral  100  generally designates a lens. Specifically, the lens  100  is adapted for use in eyeglasses worn by a computer user. As with conventional eyeglass lenses, lens  100  is made of refractive or transparent materials, such as glass or plastic. The lenses (such as lens  100 ) are, preferably, ground or molded to form optical lenses that have different focal lengths and other optical characteristics based on the needs of the wearer. Conventional eyeglass lenses are then used to treat such conditions as myopia, hyperopia, astigmatism or presbyopia. 
         [0023]    Also, as with conventional eyeglass lenses, lens  100  has topologies and arcuate profiles to refract light as needed for the specific wearer. Lens  100  comprises a first side  102  that is designed to receive light from a source and an opposite second side  104  that faces the wearer. Each of the sides  102  and  104  has a distinct arcuate profile or curvature(s), which can be seen in  FIG. 1A . As can be seen in  FIG. 1B , contour lines  106  are shown on first side  102 , which depict the different elevations or contours that appear and denote curvature. The combination of these contour features (depicted by contour lines  106 ) constitutes the topology of the first side  102 . In addition, the surfaces of one or both of sides  102  and  104  are not necessarily smooth, such as some bifocal and trifocal lenses. 
         [0024]    In addition to having different topologies and arcuate profiles, the lens can also be tinted according to the lighting requirements of the user. It has been known to tint lenses for a long period of time, but tinting was primarily done for aesthetic reasons and not functional ones. However, it has been found that having a slightly (and even a heavy) blue tint for florescent lighting conditions assists in reducing headaches and eyestrain, while yellow, rose, or lavender are better suited for incandescent lighting. Thus, it is also advantageous to provide a blue, yellow, rose, or lavender tint in lens  100 . 
         [0025]    Conventionally, lenses are ground or formed to treat vision deficiencies such as nearsightedness, farsightedness, astigmatisms, or the like. Different regions of the lenses may have different characteristics for different vision problems, for example bifocal and trifocal lenses that have lower regions formed to address near-vision defects and upper regions formed to address far-vision defects. 
         [0026]    Eyeglass wearers using computers, though, present different needs from normal, “every day” eyeglasses. Computer use presents a medium distance/field/vision difficulty not often accounted for by lens prescriptions. Specifically, according to the present invention, the topologies and curvatures of the sides  102  and  104  (i.e. the lens prescription or lens characteristics) are varied to account for height, age, and so forth so as to provide a lens that will reduce incidences of headaches and eyestrain when the wearer uses a computer. Referring to  FIG. 2A  of the drawings, the reference numeral  200  generally designates a flow chart depicting the method of determining the lens characteristics for these lens (of  FIGS. 1A and 1B ) adapted for use with a computer. 
         [0027]    This process can be done without computing tools; however, for the sake of convenience and efficiency, this method is performed in an electronic data processing system or computer. To make the calculation, a number of physical characteristics about the wearer or user are determined and then entered into the computer. In particular, the calculation uses the wearer&#39;s age (A) (entered in step  202 ), the wearer&#39;s height (H) (entered in step  204 ), the wearer&#39;s distance lens prescription (R x ) (entered in step  206 ), the wearer&#39;s average computer work distance (WD) (entered in step  208 ), and the wearer&#39;s bifocal power (ADD) (entered in step  209 ). 
         [0028]    Each of the physical characteristics, themselves, may not be sufficient to determine the necessary lens characteristics. Specifically, the age alone may simply not be sufficient and may need to be modified. Thus, in steps  210  through  220 , the corrected age is calculated and is represented by the following expressions: 
         [0000]      CA=30, if Age&lt;30   (2) 
         [0000]      CA=Age, if 30≦Age≦60   (3) 
         [0000]      CA=60, if Age&gt;60   (4) 
         [0000]    Namely, a determination is made in step  210  if a wearer is less than or equal to 30 years of age. If so, in step  212 , the corrected age is equal to 30. Otherwise, a further determination is made in step  214  as to whether a user is between 30 and 60 years of age. If so, in step  216 , the corrected age is equal to the wearer&#39;s age. Otherwise, in steps  218  and  220 , the corrected age is 60. 
         [0029]    One other physical characteristic that is modified is the height of the wearer. Based on the height (H), an adjusted number or height factor (H f ) is calculated and the formulas are as follows: 
         [0000]      H f =0, if H≧75   (5) 
         [0000]        H   f =0.75-0.01 *H , if  H&lt; 75   (6) 
         [0000]    Based on this formula, the height factor provides an adjusted number for a person under 75 inches tall. The reason for this adjusted number is that for a very tall person (notably over 75 inches tall), the distance from the screen is greater than for a shorter person. In addition, height is an important determinant on the ergonomic demands of the computer user. Thus, the prescription is adjusted slightly because shorter persons are nearer to the screen. Specifically, in step  222 , a determination is made as to whether the wearer&#39;s height is greater than or equal to 75 inches. If so, in step  224 , the height factor is set to 0. Otherwise, the height factor is calculated in accordance with equation (6) above in step  226 . 
         [0030]    Once all of the relevant factors have been calculated, the lens power is calculated in step  228 . Referring to  FIG. 2B  of the drawings, the calculation of the lens power (step  228 ) is depicted in more detail. 
         [0031]    In step  302 , the computer work distance prescription (C WD ) is calculated. The formula for calculating C WD  is as follows: 
         [0000]    
       
         
           
             
               
                 
                   
                     C 
                     WD 
                   
                   = 
                   
                     
                       
                         CA 
                         WD 
                       
                       * 
                       0.01 
                     
                     + 
                     
                       R 
                       x 
                     
                     + 
                     
                       H 
                       f 
                     
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
         [0000]    This formula essentially allows one to determine the topologies and arcuate profiles of lens  100 . In other words, equation (7) above calculates the total lens power in the absence of or with a small bifocal power, allowing an optometrist to vary the lens characteristics accordingly to allow the wearer to have a pair of eyeglasses specifically adapted for use with a computer. 
         [0032]    Under conditions, though, where a wearer uses stronger bifocal lenses, C WD  is insufficient as a sole lens characteristic. The reason for the insufficiency is that bifocal lenses allow a wearer to have different lens powers for different distances, i.e. infinite and less than 1 meter. As one can understand, the wearer&#39;s proximity to a computer monitor may fall within a distance between the lens powers, requiring one or both of the distance prescription and bifocal prescription to be adjusted accordingly. 
         [0033]    When a bifocal is used by a wearer, a computer preadd (PA) is calculated in addition to C WD  in step  304 . In particular, the formula for calculating PA is as follows: 
         [0000]        PA=R   x   +ADD−C   WD    (8) 
       This formula determines a precursor that is employed in later determining the bifocal power of a lens adapted for use with a computer. 
       [0034]    Once PA has been calculated, a determination is made as to the value of a corrected C WD  (CC WD ) in steps  306 ,  308 , and  310 . Specifically, in step  306 , C WD  is compared against the sum of R x  and ADD. If C WD  is greater than the sum of R x  and ADD, then CC WD  is equal to C WD  (step  308 ). Otherwise, CC WD  is equal to the sum of R x  and ADD (step  310 ). 
         [0035]    Then, the Distance Computer Prescription (DCR x ) or spherical base and cylindrical strength is calculated based on the value of the ADD. Specifically, in step  312 , a determination is made as to if ADD is less than 0.5. If ADD is less than 0.5, then DCR x  is equal to C WD  (total lens power in the absence of or with a small bifocal power as stated above) in step  316 . Otherwise, DCR x  is equal to CC WD  in step  314 . 
         [0036]    In addition to calculating the DCR x , the bifocal power for the computer use lenses (CpA) is determined in steps  318 ,  320 , and  322 . In step  318 , a determination is made as to whether PA is less than 0.3. If so, CpA is equal to PA (step  320 ). Otherwise, CpA is zero (step  322 ). 
         [0037]    Furthermore, the above method can be further applied to contact lenses. In step  324 , a determination is made as to if contact lenses are used, and in step  326  the contact lens prescription (CLR x ) is entered. The contact lens DCR x  is set equal to DCR x  (calculated in steps  312 ,  314 , and  316 ) minus CLR x  in step  328 . Additionally, the contact lens bifocal power is set equal to CpA in step  330 . 
         [0038]    Thus, an optometrist is able to easily calculate all of the lens characteristics that are standard components of lens prescriptions for these lenses that are adapted for use with a computer. More particularly, the optometrist can utilize a very simple automated system or program to calculate large numbers of prescriptions for lenses adapted for use with computers with ease and with a reduced number of errors. 
         [0039]    Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.