Abstract:
A subjective ophthalmic refractor is improved for operator visibility in a darkened examination room by forming a cylinder axis scale of the refractor as a light-transmitting component having opaque scale gradations and installing a polar array of illumination sources to project light through the cylinder axis scale, which preferably includes a translucent material for diffuse illumination. In an alternative embodiment, the cylinder axis scale includes a photoluminescent material to which the scale gradations are applied. The refractor is further improved by installing respective illumination sources near a cylinder power readout and a sphere power readout of the refractor. The disclosure additionally relates to a method for retrofitting an ophthalmic refractor to illuminate the cylinder axis scale, cylinder power readout, and sphere power readout.

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to ophthalmic instruments, and more particularly to subjective ophthalmic refractors for evaluating refractive characteristics of a patient&#39;s eye. 
     II. Description of the Related Art 
     A subjective ophthalmic refractor typically comprises left-eye and right-eye batteries each having a defined viewing path along which an operator may selectively introduce combinations of testing lenses having known refractive properties. During examination, the patient is positioned in a darkened room with his or her eyes aligned to view a projected target chart along the viewing paths defined by the left-eye and right-eye batteries. The operator then performs well-known refracting procedures, including refraction using astigmatic charts and the Jackson cross-cylinder test. A goal of the examination procedure is to determine the sphere power, cylinder power, and cylinder axis of each eye in order to prescribe a suitable pair of corrective lenses. 
     In order to assess sphere power, the operator must rotate a strong sphere control knob and a weak sphere dial on the associated refractor battery to position chosen spherical power lenses in series in the viewing path. The numerical diopter value of the resultant sphere power introduced in the viewing path is reported to the operator by a sphere power readout provided on the refractor battery. A rotatable cylinder power control knob enables the operator to adjust the power of a cylinder lens introduced in the viewing path, and a numerical diopter value of the cylinder power is displayed by a cylinder power readout on the refractor battery. The axis orientation of the cylinder lens is controlled by a cylinder axis knob that includes a pair of diametrically opposite cylinder axis pointers. The cylinder axis knob is mounted for rotation relative to a coaxially arranged cylinder axis scale circumferentially surrounding the cylinder axis knob and having angular scale gradations. Typically, the scale gradations are marked in five-degree increments, and two complementary protractor scales of one-hundred eighty degrees surround the cylinder axis knob. 
     Because the examination room is darkened for purposes of target chart projection, the task of reading the sphere power and cylinder power readouts, and of finding the location of the cylinder axis pointers with respect to the cylinder axis scale, is a difficult one for the operator. During the course of a day in which the operator sees many patients, fatigue becomes a factor and the likelihood of errors in reading the refraction data increases. Operators have been known to use a pocket ophthalmoscope to illuminate the sphere and cylinder power readouts and the cylinder axis scale, however this is not the intended use of an ophthalmoscope. 
     The R. H. Burton Company of Grove City, Ohio has addressed this problem by providing an ophthalmic refractor wherein the sphere power readout, the cylinder power readout, and the cylinder axis scale are illuminated according to an arrangement described in U.S. Pat. No. 5,281,984. This patent teaches the use of a single light bulb supplying light to a light guide mounted on the refractor battery housing of each refractor battery. The light guide is formed of transparent material and is configured to provide a first transparent output around the periphery of the cylinder axis scale, a second transparent output adjacent to the cylinder power readout, and a third transparent output adjacent to the spherical power readout. While this arrangement solves the problem in a suitable manner, it does have certain drawbacks. For example, when the bulb burns out, illumination is ceased at the sphere power readout, the cylinder power readout, and the cylinder axis scale all at once. Another drawback is that the specially configured light guide is not retrofittable to older refractor models from R. H. Burton Company and to ophthalmic refractors from other manufacturers. Finally, the patent contains no teaching of how to arrange a power supply cord connected to the bulb in a manner that will not interfere with the patient or operator. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide an ophthalmic refractor with means for illuminating a sphere power readout, a cylinder power readout, and a cylinder axis scale of the refractor such that they may be readily and clearly viewed by an operator in a darkened examination room. 
     It is another object of the present invention to provide an ophthalmic refractor with means for independently illuminating a sphere power readout, a cylinder power readout, and a cylinder axis scale of the refractor such that an illumination source failure with respect to one of these elements does not affect illumination of the other elements. 
     It is a further object of the present invention to provide an ophthalmic refractor with means for connecting a power source to various illumination sources thereof such that power cords or the like are unobtrusive to the patient and operator. 
     It is a further object of the present invention to provide an ophthalmic refractor with means for illuminating a sphere power readout, a cylinder power readout, and a cylinder axis scale of the refractor that is retrofittable to a wide range of ophthalmic refractor models. 
     It is a further object of the present invention to provide a method of retrofitting an ophthalmic refractor with means for illuminating a sphere power readout, a cylinder power readout, and a cylinder axis scale of the refractor. 
     The present invention involves improvement of a subjective ophthalmic refractor of the type comprising left-eye and right-eye batteries, a mounting bracket for pivotally suspending the left-eye and right-eye batteries from a stand, each battery having a patient viewing path, a strong sphere control knob for selectively positioning a strong sphere lens of chosen power in the patient viewing path, a weak sphere control dial for selectively positioning a weak sphere lens of chosen power in the patient viewing path, a sphere power readout for displaying the cumulative power of the chosen strong and weak sphere lenses to an operator, a cylinder power knob for selectively positioning one or more cylinder lenses of chosen power in the patient viewing path, a cylinder power readout corresponding to the cylinder power knob for displaying the resultant power of the cylinder lenses to an operator, a polar cylinder axis scale, and a cylinder axis knob coaxial with and rotatable relative to the cylinder axis scale for adjusting the cylinder axis of the cylinder lenses, wherein the cylinder axis knob includes at least one cylinder axis pointer cooperating with the cylinder axis scale for indicating the cylinder axis to an operator. An ophthalmic refractor of the above-mentioned type is improved by forming the cylinder axis scale as a light-transmitting component having opaque scale gradations, and installing a polar array of illumination sources arranged to project light through the cylinder axis scale. The cylinder axis scale preferably includes a translucent material for diffuse illumination. In an alternative embodiment, the cylinder axis scale simply includes a photoluminescent material having scale gradations applied thereto. To enhance the visibility of the cylinder axis pointers with respect to the cylinder axis scale, the cylinder axis pointers are preferably formed as light-transmitting areas on the cylinder axis knob that overlap with the cylinder axis scale, or the pointers are opaque markings on an annular translucent flange overlapping with the cylinder axis scale. 
     The ophthalmic refractor is further improved by installing a cylinder power illumination source near the cylinder power readout, and by installing a sphere power illumination source near the sphere power readout. 
     In a preferred embodiment of the invention, the light sources are light-emitting diodes connected to a power source via a slip ring arranged to conduct electricity through the pivotal connection between the mounting bracket and the remainder of the refractor, whereby external power cords in the region of the patient or the operator can be avoided. 
     The invention further encompasses a method for retrofitting an ophthalmic refractor of the above-mentioned type. The method comprises the steps of removing the cylinder axis knob and cylinder axis scale from each battery housing, opening each battery housing, fixing a polar array of illumination sources within each battery housing, arranging power lines leading to each polar array of illumination sources for enabling a power source to be connected the arrays, closing each battery housing, and installing a replacement cylinder axis scale over each polar array of illumination sources, the replacement cylinder axis scale being formed as a light-transmitting component having opaque scale gradations, and mounting either the original cylinder axis knob or a replacement cylinder axis knob to be coaxial with the replacement cylinder axis scale. Where the original cylinder axis knob is reused, machining a cut-out area in place of a cylinder axis pointer on the cylinder axis knob is a preferred additional retrofit step. The method preferably comprises the further steps of installing a cylinder power illumination source in each battery housing proximate the respective cylinder power readout, and installing a sphere power illumination source in each battery housing proximate the respective sphere power readout. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
     FIG. 1 is a front elevational view of an ophthalmic refractor formed in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a side elevational view thereof; 
     FIG. 3 is a rear elevational view of a right-eye battery of the ophthalmic refractor shown in FIGS. 1 and 2; 
     FIG. 4 is a front elevational view of the right eye-battery shown in FIG. 3; 
     FIG. 5 is a transparent perspective view of the right eye battery shown in FIG. 3, with knobs removed for sake of clarity; 
     FIG. 6 is a view taken generally along the section line I—I in FIG. 3; 
     FIG. 7 is a view taken generally along the section line II—II in FIG. 4; 
     FIG. 8 is a cross-sectional view showing an alternative construction of a cylinder axis scale in accordance with the present invention; 
     FIG. 9 is cross-sectional view showing another alternative construction of a cylinder axis scale in accordance with the present invention; and 
     FIG. 10 is a view taken generally along the section line III—III in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is directed initially to FIGS. 1 and 2 of the drawings showing an ophthalmic refractor  10  having a left-eye battery  12 L and a right-eye battery  12 R. Batteries  12 L and  12 R depend from an upper slider track  14  held by a central support  15  of refractor  10  to allow for adjustment of interpupillary distance to fit the patient. Central support  15  is pivotally connected to a mounting bracket  16 , whereby the refractor  10  can be supported on a stand (not shown) and positioned in front of the face of a patient. Right-eye battery  12 R will now be described in further detail, it being understood that left-eye batter  12 L is a mirror image of the right-eye battery. 
     Right-eye battery  12 R includes a housing  18  comprising a front half-shell  20  and a rear half-shell  22 , and a viewing path  24  through the housing. Referring also now to the sectional view of FIG. 6, it can be seen that housing  18  encloses a strong sphere lens disc  26  carrying a plurality of strong sphere lenses  28  each having a different optical power. For example, strong sphere lens disc  26  preferably includes a polar array of twelve sphere lenses (including a zero-power opening) differing in power by steps of three diopters, and is rotatable by means of a strong sphere control knob  30  operatively connected thereto for enabling an operator to position a chosen strong sphere lens in viewing path  24 . Housing  18  also encloses a weak sphere lens disc  32  having a plurality of weak sphere lenses  34  each having a different optical power. For example, weak sphere lens disc  32  preferably includes a polar array of twelve sphere lenses (including a zero-power opening) differing in power by steps of one-quarter diopter, and is rotatable by means of a weak sphere dial  36  to allow the operator to position a chosen weak sphere lens in viewing path  24 . The chosen strong sphere lens  28  and weak sphere lens  34  combine in an additive manner to provide a resultant refracting sphere power along viewing path  24 . In the ULTRAMATIC® RX MASTER PHOROPTOR® refracting instrument manufactured by Reichert Ophthalmic Instruments, a division of Leica Microsystems Inc. (assignee of the present application), the resultant sphere power can be adjusted through a range from −19.00 diopters through +16.75 diopters in quarter diopter increments. The numerical diopter value of the resultant sphere power is displayed at a sphere power readout  38  visible through a transparent cover portion  40  of housing  18 . 
     Housing  18  further encloses a strong cylinder lens carrier  42  comprising an array of strong cylinder lenses  44  (including a zero-power opening), and a weak cylinder lens carrier  46  comprising an array of weak cylinder lenses  48  (including zero-power openings). Cylinder lens carriers  42  and  46  are rotatably mounted within housing  18 , and cylinder lenses  44  and  48  are specified according to a graded series of cylinder power. The rotational positions of cylinder lens carriers  42  and  46  are controlled in tandem by rotating a cylinder power knob  50  operatively linked to cylinder lens discs  42  and  44 , whereby different combinations of a strong cylinder lens  44  and a weak cylinder lens  48  are positionable in viewing path  24 . By way of example, in the PHOROPTOR® refracting instrument mentioned above, the resultant cylinder power can be adjusted through a range from 0.00 diopters through 6.00 diopters in quarter diopter increments. The numerical diopter value of the resultant cylinder power is displayed at a cylinder power readout  52  through housing  18  near cylinder power knob  50 . 
     The strong cylinder lenses  44  and weak cylinder lenses  48  are mounted in their respective carriers  42  and  46  by lens holders  54  that enable rotation of each cylinder lens relative to the carrier about an axis of the lens, thereby allowing for adjustment of the cylinder axis orientation. When a selected strong cylinder lens  44  and weak cylinder lens  48  are aligned in viewing path  24 , a cylinder axis knob  56  is operatively linked to lens holders  54  such that rotation of cylinder axis knob  56  causes a corresponding rotation of the lens holders  54  and the associated strong and weak cylinder lenses for adjustment of the cylinder axis. A polar cylinder axis scale  58  is fixedly mounted on housing  18 , and more particularly on a turret island  19  of housing  18 , in coaxial surrounding relation to cylinder axis knob  56 , which includes a pair of diametrically opposite cylinder axis pointers  60  pointing to angular gradations indicated on cylinder axis scale  58 . Once again by way of example, the cylinder axis scale of the PHOROPTOR® refracting instrument provides two complementary 180° protractor scales having angular values indicated at five-degree intervals. Thus, the operator rotates cylinder axis knob  56  to adjust the angular orientation of the cylinder axis, and this orientation is indicated by the location of cylinder axis pointers  60  with respect to cylinder axis scale  58 . 
     To this point in the detailed description, the elements of ophthalmic refractor  10  are well-known as prior art and are generally familiar to ophthalmic practitioners. The present invention departs from the prior art, and represents an improvement in ophthalmic refractors of the type described above, with respect to illumination of the cylinder axis scale  58 , the cylinder power readout  52 , and the sphere power readout  38  of ophthalmic refractor  10 . 
     Attention is directed now to FIGS. 5 through 7, wherein an arrangement for illuminating cylinder axis scale  58  is shown. More specifically, the cylinder axis scale  58  is formed as a light-transmitting component having opaque scale gradations  62 , and a polar array of illumination sources  64  is arranged to project light through the light-transmitting cylinder axis scale. In a preferred embodiment, illumination sources  64  are light-emitting diodes on a flexible circuit board  66  installed behind cylinder axis scale  58  within a bore  61  through turret island  19 . Cylinder axis scale  58  is preferably formed of a translucent material, resulting in a diffusely illuminated cylinder axis scale and substantially eliminating localized bright spots at locations corresponding to illumination sources  64 . The scale gradations  62  can be printed or otherwise applied directly to the front surface of cylinder axis scale  58 , and are preferably opaque for sake of contrast. In an alternative construction shown in FIG. 8, cylinder axis scale  58 ′ is formed in two layers fixed to one another. A first layer  68  closest to illumination sources  64  is formed of a translucent material for light diffusion, and a second layer  70  is formed of a transparent material that lends itself more readily to printing or otherwise applying scale gradations  62 . 
     The present invention encompasses another alternative construction of cylinder axis scale  58 ″ according to FIG.  9 . Here, cylinder axis scale  58 ″ is made of a photoluminescent material  72  having scale gradations  62  applied thereto. Consequently, cylinder axis scale  58  “glows in the dark,” and its luminescence is recharged when the examination room lights are brightened. 
     While illumination of cylinder axis scale  58  as described above substantially solves the problem with respect to enabling the operator to comfortably read the cylinder axis angle, it is nevertheless desirable to also improve the visibility of cylinder axis pointers  60  on cylinder axis knob  56  in conjunction with the cylinder axis scale. Because pointers  60  are commonly provided on a beveled flange portion  74  of cylinder axis knob  56  that overlaps an inner annular region of cylinder axis scale  58 , pointers  60  can be formed as light-transmitting areas  76  through flange portion  74 , as shown in FIGS. 6 and 7. In a particularly simple reduction to practice, light-transmitting areas  76  are cut-out areas formed through flange portion  74 . Another possible approach is to construct beveled flange portion  74  from a transparent or translucent material, and applying opaque markings as pointers  60  to the flange portion. 
     The problem of illuminating cylinder power readout  52  is solved, according to the present invention, by providing a cylinder power illumination source  78  near cylinder power readout  52  as depicted in FIG.  7 . Cylinder power illumination source  78  is independent from the array of illumination sources  64  described above, and is dedicated solely to the illumination of cylinder power readout  52 . In a currently preferred construction, cylinder power illumination source  78  is a light-emitting diode and, due to the proximity of cylinder power readout  52  to cylinder axis scale  58 , is provided on the same circuit board  66  that carries the polar array of illumination sources  64 . Cylinder power illumination source  78  can be located along an edge of turret island  19  as shown in FIG.  3 . 
     Similarly, at least one sphere power illumination source  80  is located near sphere power readout  38  for enhancing visibility of the readout, as can be understood with reference to FIGS. 5 and 9. FIG. 5 shows two slightly spaced illumination sources  80 , however one central illumination source  80  may also be used with desired results. Illumination sources  80  are preferably light-emitting diodes on a flexible circuit board  82  fastened to the inside surface of a wall  84  of housing  18  that extends alongside sphere power readout  38  and abuts with an edge of transparent cover portion  40 , with corresponding portals  86  being provided through wall  84  to allow light to reach the area of sphere power readout  38 . 
     The circuit boards  66  and  82  are connected in series by wires  88  and  90  for connecting a power source to the various illumination diodes. In order to keep power cords out of the way of both the patient and the operator, wire  88  is preferably routed through housing  18  and central support  15  to the location where the central support is pivotally connected to mounting bracket  16 . In accordance with the present invention, a slip ring  92  is provided to conduct current across the pivot junction between central support  15  and mounting bracket  16 . The wiring then continues as wire  93  through mounting bracket  16  to an externally accessible female connection jack  94  on the mounting bracket which receives a male plug (not shown) from a power transformer (also not shown) connected to a wall outlet. 
     A major advantage of the refractor illumination scheme of the present invention is that it is well suited for application to existing ophthalmic refractors through a retrofitting procedure. During a retrofit in accordance with the present invention, cylinder power knob  50 , cylinder axis knob  56 , and cylinder axis scale  58  are removed from housing  18 . Typically, these elements are removably attached using readily accessible set screws. Other elements, such as a cross-cylinder and prism turret  17  and turret island  19  are also removed as necessary to permit housing  18  to be opened by unscrewing fasteners that hold front half-shell  20  and rear half-shell  22  together. In preparation for sphere power illumination source  80 , portal  86  is machined through the wall  86 . Circuit boards  66  and  82  are then fixed in place by adhesive, screws, or other suitable means, and power lines  88  and  90  leading thereto are arranged to extend within open spaces in housing  18 . A hole may be drilled through the housing to permit a connection jack to be mounted for external access, or a slip ring  92  may be installed at the mounting bracket as described above to allow less conspicuous arrangement of the wiring leading to a more remotely located connection jack. The battery housing is then closed by reattaching front half-shell  20  to rear half-shell  22 . 
     Next, light-transmitting cylinder axis scale  58  is installed in place of the original cylinder axis scale overtop the ring of diodes  66  on circuit board  66 . The original cylinder axis knob  56  can then be replaced, preferably after machining cut-out areas defining cylinder axis pointers  60 . As an alternative, a new pre-fabricated cylinder axis knob can be installed that already has cut-out areas defining pointers  60 , or that has a translucent flange portion  74  with opaque pointer markings. The original cylinder power knob  50  is reinstalled to complete reassembly. 
     As will be appreciated from the foregoing description, the improvement and method of the present invention provide reliable and effective illumination of the cylinder axis scale, cylinder power readout, and sphere power readout of a conventional ophthalmic refractor using commercially available components. The invention is applicable to original equipment to help new purchasers, and through retrofit to help existing ophthalmic refractor users.