Apparatus for determining prescription for prism lenses for diplopic patients

An apparatus is provided for finding and defining a prescription for prism glasses for Diplopic patients and AMD patients whose Macula and Fovea are damaged enough that the patients have double vision, but, still have relatively good acuity. The apparatus positions lenses in infinitely variable locations horizontally and vertically in front of the patient's eyes until the patient indicates that he/she sees the two images fuse. The H-V coordinates of the location of the Optic center of each lens axis in relation to the patient's visual axis are decentration dimensions indicated for each eye by the H and V dials on the apparatus and are thus the basis for an accurate prescription for prism lenses.

BACKGROUND

Many people suffering from Adult-onset Macular Degeneration (AMD) have damage to the Macula that has repositioned the Fovea (center of the Macula) causing a new visual-axis to be slightly offset from the original (normal) visual-axis. This is very common in older people. The result, in many cases, is Diplopia. Double vision occurs when the image that one eye sees does not coincide with the image that the other eye sees when looking with both eyes at the same time at the same physical object, making it appear that there are two of everything in the field of view of the Macula and Fovea. The brain can accommodate for slight differences, but, when the offset becomes too great for the brain to accommodate-double vision results. Peripheral vision is not affected by AMD.

Many AMD patients still have relatively good acuity in the AMD eye but the offset of the visual-axis still results in double vision. For patients with AMD in both eyes, the result most likely will be double vision. Another cause of double vision is Strabismus of which there are several types and which sometimes is a result of the right and left eye muscles' inability to coordinate to focus in on an object and make the two images fuse. Double vision sufferers have to find their own method of coping with the problem. For some people, surgery is the answer. For the other people, one way to cope is to close one eye while viewing. This quickly becomes tiring. Another method is to wear an eye-patch instead of closing the eye. The eye-patch interferes with eyeglasses making that option also unsatisfactory. A problem with both methods is that the person loses the peripheral vision in that eye. Losing peripheral vision can actually be dangerous if the person is in a dangerous industrial setting, or driving a vehicle where it is important to see danger approaching with the periphery of one's vision. One crude method of addressing the problem has been the use of Prism Bars held in front of one eye by Ophthalmologists to guess at the amount of induced prism required in eyeglass lenses by the patient to bring the two images together as one. That method is not accurate and has been the source of much dissatisfaction on the part of patients as well as the Ophthalmologists. There are also hand held rotary prisms available. Here again hand held means not very accurate.

Thus, there has always been a need for a more accurate and satisfactory way of improving the seeing ability of such individuals.

SUMMARY

I have had AMD for a number of years and relied on the methods mentioned in the BACKGROUND above and found them to be very unsatisfactory. I was constantly on the lookout for a way that was better. I noticed one day, while using a magnifying glass, that as the magnifying glass is moved across a page in one direction that the words on the printed page appeared to move in the opposite direction. Well, that was not news to me. What was new was me thinking that there may be a new way to use the prism effect. So I theorized that if my reading glasses lens were relocated within their frames, let's say move one up and out (away from the nose) and the other one down and out in infinitely variable distances and combinations, that at some point an image of an object would focus on the center of each Fovea of my two eyes. In other words, the images might be relocated just the exact distance and direction to fuse and appear to me as one image (single vision) instead of two images (double vision) for each object viewed. Through experimentation I found my theory to be correct. As a matter of fact, it worked even better than I had hoped. So, it became obvious to me that there was a need for an apparatus that could quickly and accurately determine what those distances and directions are for any Diplopic patient. Those distances and directions plus the diopter strengths (and other requirements of the eye) would then be the prescription for eyeglass lenses for a Diplopic patient. Hereinafter those distances and directions are referred to as “offset distances (H-V coordinates)”. Ideally the apparatus should be infinitely variable within its limits, and would split the induced prism equally but oppositely between the two lenses, to provide maximum accuracy and comfort.

DETAILED DESCRIPTION

All references to “right” and “left” in these Specifications and Claims are relative to the patient's perspective while viewing through a right lens29and a left lens30shown inFIG. 7, the front view of the preferred embodiment, also further clarified by the graphic of a patient's-eye74shown inFIG. 9, a side view.

Like referenced elements are represented by like reference numbers throughout the drawings. Referenced components shown in a particular Figure but not described therein under that Figure's heading is because the referenced component has already been described in detail in a discussion of a previous Figure.

FIG. 1is a side orthographic view of a normal eye (Emsley Standard Reduced 60-diopter eye) hereinafter referred to as ESR60-DE2A, and it is assumed that it is normal except for farsightedness. Here it is shown viewing an object7through a first-magnifying-lens6A the diopter strength of which has been determined by a conventional eye exam. A first-image8A of the object7is formed upside down on a first-Fovea4A and surrounding first-Macula5A (size exaggerated for clarity). Surrounding the first-Macula5A is a first-Retina11A. For the purpose of illustrating how the first-image8A is formed, light rays emanating from the object7, and a first-magnifying-lens-axis3A, and a first-visual-axis1A are also shown.

FIG. 2is an orthographic side view of an eye (Emsley Standard Reduced 60-diopter eye) hereinafter referred to as AMD-ESR60-DE2B, and it is assumed that in addition to farsightedness it is affected by AMD. Here it is shown viewing the object7through a second-magnifying-lens6B. In this view the effects of AMD has shifted a second-Fovea4B downward a small second-distance10. A second-magnifying-lens-axis3B of the second-magnifying-lens6B is shifted upward an exact first-distance9required to cause a second-image8B to form on the center of the second-Fovea4B and (if large enough), on a second-Macula5B which will make the object7appear to be in the same location in space as the normal eye (without AMD) sees it. Surrounding the second-Macula5B is a second-Retina11B. Thus with both eyes focusing on the object7the two images fuse.

If the second-magnifying-lens-axis3B were to be aligned with a second-visual-axis1B, that existed prior to the onset of AMD, then with both eyes open, the patient would see two separate objects7(one above the other). This is the case because the image formed in AMD-ESR60-DE2B would not be centered on the second-Fovea4B as it is in ESR60-DE2A, thus the patient would see two objects7that do not fuse (coincide).

Where a negative diopter lens is required for the patients eye, the image will be shifted in a direction that is opposite to the direction of a positive diopter lens.

FIG. 3is a graphic representation of how a standard Amsler Grid looks to a pair of normal eyes. It also represents how a standard Amsler Grid looks to a pair of eyes in which one or both of them has mild AMD but are viewing through prism lenses embodying the principles of the present invention. The Amsler Grid may appear slightly blurry due to mild loss of acuity caused by AMD, but the lines will appear straight. Prism lenses inherently introduce slight blurring caused by dispersion.

FIG. 4is a graphic representation of how the standard Amsler Grid might look to an eye with mild AMD, such as AMD-ESR60-DE2B, viewing through an ordinary magnifying lens, where the Fovea4B (center of the Macula) has shifted downward the small second-distance10away from the normal second-visual-axis1B.

FIG. 5is a graphic representation of how the alphabetical character “A” might look to a person viewing it with both eyes where one eye has a mild case of AMD such as AMD-ESR60-DE2B, in which the Fovea4B has shifted slightly downward away from the normal visual-axis1B. The other eye could be normal such as ESR60-DE2A or it could have mild AMD like AMD-ESR60-DE2B but with the offset in a different direction and/or a different distance. A tiny shift is accommodated for by the brain which makes the viewer see only one “A”, but eventually as the distortion becomes greater and greater, the brain can no longer accommodate so that the viewer then sees double. In this case, one “A” above another.

FIG. 6is a graphic representation of how the alphabetical character “A” will look to a person with normal vision in both eyes. The images formed on the first-Fovea4A and the first-Macula5A of the two eyes fuse and appear to the viewer as one object. It also represents how the alphabetical character “A” might look to a pair of eyes in which one or both of them has mild AMD but are viewing through prism lenses made using the principles of the present invention. The image may appear slightly blurry due to mild loss of acuity due to AMD and blurring due to dispersion.

Although the present inventor was able to make a pair of reading glasses by trial and error by using the principles of the present invention and the scientific principles described inFIG. 1andFIG. 2, there needed to be an apparatus employing the principles of the present invention that would provide a quicker and more accurate way to find and define a prescription (Rx) for prism lenses. The present inventor did conceive such an apparatus and it is the “preferred embodiment” shown in the Drawings,FIG. 7throughFIG. 13andFIG. 15throughFIG. 18. Plain spherical lenses with a diopter strength appropriate for a patient could be positioned in lens holders in front of the patient's eyes by an apparatus having an infinitely variable graduated horizontal control that moves the pair of lens holders slowly in front of the patients eyes equal distances but in opposite directions and, independently from the horizontal control, an infinitely variable graduated vertical control could slowly move the lens holders in front of the patients eyes equal distances but in opposite directions. The horizontal control could be operated until the patient sees two vertical lines fuse, then the vertical control could be operated until the patient sees two horizontal lines fuse-induced prism by decentration. The numbers on the controls would then be the basis for a prism Rx for the patient. The preferred embodiment described herein satisfies all of those criteria.

FIG. 7andFIG. 8illustrate the front view and a partial enlarged front view respectively of the preferred embodiment, employing the principles of the present invention. Components pertinent to the discussion ofFIG. 7andFIG. 8but that are more clearly shown in other Figures are so noted. The front view clearly shows linkages between a horizontal-adjustment-knob50(a first human interface) and a user selectable right-lens-blank29. Likewise linkages between the horizontal-adjustment-knob50and a user selectable left-lens-blank30are shown. A vertical-adjustment-knob49(a second human interface) is shown linked to the right-lens-blank29. Likewise linkages between the vertical-adjustment-knob49and the left-lens-blank30are shown. These linkages provide the basic motions necessary for the lenses, but, more detail is provided below for greater clarity.

Horizontal Control: Horizontal movement of the right-lens-blank29begins with the horizontal-adjustment-knob50that has a first-central-hole89(FIG. 13) along its axis sized to accept a horizontal-pinion-axle56that passes through the first-central-hole89(FIG. 13) and is prevented from rotating within the horizontal-adjustment-knob50by a first-setscrew84. Further, the horizontal-pinion-axle56passes through a slip-fit-hole76(FIG. 13) in a bearing-plate86and through a horizontal-pinion70(FIG. 13) and finally terminates in a bearing-hole88(FIG. 13) in a horizontal-guide31. The bearing-plate86is held in place with four bearing-plate-fasteners87. A locknut72(FIG. 13) on the horizontal-pinion-axle56confines the horizontal-pinion70(FIG. 13) to it's required position on the horizontal-pinion-axle56. The portion of the horizontal-pinion-axle56that fits within the horizontal-pinion70(FIG. 13) is non-round in cross section matching a non-round-hole91(FIG. 13) in the center of the horizontal-pinion70(FIG. 13) whereby any rotation of the horizontal-adjustment-knob50results in an equal rotation of the horizontal-pinion70(FIG. 13).

The horizontal-guide31has a bottom-horizontal-T-shaped groove80(FIG. 13) and a top-horizontal-T-shaped-groove81(FIG. 13) running parallel to each other and spaced apart far enough to accommodate a bottom-horizontal-rack33and a top-horizontal-rack34, each respective rack has a T-shaped cross section that matches and engages the T-shaped grooves in the horizontal-guide31wherein the horizontal-pinion70(FIG. 13) is juxtaposed between and engages both the bottom-horizontal-rack33and the top-horizontal-rack34causing them to slide equal distances but in opposite directions when the horizontal-adjustment-knob50is rotated.

A right-vertical-rod37is fixedly attached to a right end of the bottom-horizontal-rack33through the use of a vertical-rod-fastener57and two right-lateral-stability-pins77integral to the right-vertical-rod37and the right-vertical-rod37is vertically slidably connected to a right-vertical-rod-bushing60which is integral to a right-lens holder62so that the right-lens-holder62is free to slide vertically along the length of the right-vertical-rod37when it is propelled to do so by a right-horizontal-rod39, but its horizontal movement is restrained by the right-vertical-rod37. The end result of the foregoing detailed linkages is that horizontal motion of the bottom-horizontal-rack33imparts an equal motion to the right-lens-holder62.

A left-vertical-rod38is fixedly attached to a left end of the top-horizontal-rack34through the use of the vertical-rod-fastener57and two left-lateral-stability-pins78integral to the left-vertical-rod38and the left-vertical-rod38is vertically slidably connected to a left-vertical-rod-bushing61which is integral to a left-lens holder63so that the left-lens-holder63is free to slide vertically along the length of the left-vertical-rod38when it is propelled to do so by a left-horizontal rod40, but its horizontal movement is restrained by the left-vertical-rod38. The end result of the foregoing detailed linkages is that horizontal motion of the top-horizontal-rack34imparts an equal motion to the left-lens-holder63.

Vertical Control: Vertical movement of the right-lens-blank29begins with the vertical-adjustment-knob49that has a second-central-hole90(FIG. 12) along its axis sized to accept a vertical-pinion-axle55that passes through the second-central-hole90and is prevented from rotating within the vertical-adjustment-knob49by a second-setscrew85. Further, the vertical-pinion-axle55passes through a second-slip-fit-hole93(FIG. 12) in a vertical guide32and through a vertical-pinion71(FIG. 12). The locknut72(FIG. 12) on the vertical-pinion-axle55confines the vertical-pinion71(FIG. 12) to its required position on the vertical-pinion-axle55. The portion of the vertical-pinion-axle55that fits within the vertical-pinion71(FIG. 12) is non-round in cross section matching a non-round-hole92(FIG. 12) in the center of the vertical-pinion71(FIG. 12) whereby any rotation of the vertical-adjustment-knob49results in an equal rotation of the vertical-pinion71(FIG. 12).

The vertical-guide32has a right-vertical-T-shaped-groove82(FIG. 12) and a left-vertical-T-shaped-groove83(FIG. 12) running parallel to each other and spaced apart far enough to accommodate a right-vertical-rack35and a left-vertical-rack36, each respective rack has a T-shaped cross section that matches and engages the T-shaped grooves in the vertical-guide32wherein the vertical-pinion71(FIG. 12) is juxtaposed between and engages both the right-vertical-rack35and the left-vertical-rack36causing them to slide equal distances but in opposite directions when the vertical-adjustment-knob49is rotated.

The right-horizontal-rod39is tightly threaded into a bottom end of the right-vertical-rack35and the right-horizontal-rod39is horizontally slidably connected to a right-horizontal-rod-bushing58which is integral to the right-lens-holder62so that the right-lens-holder62is free to slide horizontally along the length of the right-horizontal-rod39when it is propelled to do so by the right-vertical-rod37, but its vertical movement is restrained by the right-horizontal-rod39. The end result of the foregoing detailed linkages is that vertical motion of the right-vertical-rack35imparts an equal motion to the right-lens-holder62.

The left-horizontal-rod40is tightly threaded into a bottom end of the left-vertical-rack36and the left-horizontal-rod40is horizontally slidably connected to a left-horizontal-rod-bushing59which is integral to the left-lens-holder63so that the left-lens-holder63is free to slide horizontally along the length of the left-horizontal-rod40when it is propelled to do so by the left-vertical-rod38, but its vertical movement is restrained by the left-horizontal-rod40. The end result of the foregoing detailed linkages is that vertical motion of the left-vertical-rack36imparts an equal motion to the left-lens-holder63.

Crosshairs and Lens-holders: The user selectable right-lens-blank29is forced into a groove in the right-lens-holder62and is held in place by tension due to the right-lens-holder62having a slightly smaller diameter than the right-lens-blank29by an amount sufficient to prevent the right-lens-blank29from falling out; likewise for the left-lens-blank30and the left-lens-holder63.

Zeroing: It is important to provide a pair of plano lenses with crosshairs thereon in the set of lenses that are provided for use in conjunction with the preferred embodiment. A zeroing thumbscrew46(FIG. 8) is loosened. With the lenses in place the right-lens-blank29and the left-lens-blank30can be accurately centered on the patient's eyes. This is done by adjusting a spacing of the pair of crosshairs by rotating the horizontal-adjustment-knob50until the spacing of the pair of crosshairs matches a spacing of the patient's P.D.

At this point (after aligning crosshairs with eyes) a rotatable circular horizontal-scale48(FIG. 8) is rotated until zero on the scale aligns with a single horizontal-index52printed on the horizontal-adjustment-knob50and the zeroing-thumbscrew46is tightened thereby clamping the horizontal-scale48between a washer54and the bearing-plate86. This is called “zeroing” the scale and splits the horizontal “offset” distance (determined during an examination of a patient) equally but oppositely between the right and left lenses.FIG. 14provides more detail regarding offset (decentration).

Lens Sets: Lens sets for use in conjunction with the lens-holders62and63of the Preferred Embodiment generally include the most popular centered-lens diopters in both plus and minus powers. These lenses29and30are edged to fit the lens holders62and63and have a segment removed from them to prevent interference when the two lenses are moved toward each other. In that position (centers of the lenses closer than the patient's P.D.), the two flat parts of the lenses face each other allowing the centers of the lenses to be closer together without interference. If the patient's eyes are such that the centers of the lenses must be located farther apart than the patient's P.D., the flat parts of the lenses are rotated away from each other so that there will be more viewable lens area available. Decentered lens sets are also provided for use in conjunction with the lens-holders62and63of the Preferred Embodiment and generally include the most popular Diopters in both plus and minus powers for each of at least three sub-sets of decentered lenses of varying degrees of decentration up to and a maximum of 70 mm of decentration. These lenses29and30are edged to fit the lens holders62and63. Lens sets for use in conjunction with the lens-holders99of the Preferred Embodiment generally include the most popular centered lens diopters in minus powers. These lenses98are smaller than the lenses29and30.

User Instructions: The horizontal-scale48and the vertical-scale47are both circular scales with millimeter indications ranging from zero to fifteen on each side of a zero. On both scales the right side numerals and indexes are red and on the left side are blue. This is a color code for use with a user-instructions44that clearly indicates whether a number on the horizontal-scale48aligned with the horizontal-index52is indicating a distance that is BI or BO for the patient's OD and BI or BO for the patient's OS. Likewise for a number aligned with the vertical-index51, the color code in the instructions44indicates whether the distance is BU or BD for the patient's OD and BU or BD for the patient's OS.

Interfacing with an articulated arm: A top extension of the vertical-guide32is formed to accept a fitting on a commercially available articulated-arm79(FIG. 7) that can be used for positioning the preferred embodiment in front of the patient's eyes. SeeFIG. 9for a description of four front-lugs41and four lug-fasteners43.

FIG. 9illustrates the side view of the preferred embodiment, employing the principles of the present invention. A transparent-gear-cover73, and transparent-gear-cover-fasteners75are described underFIG. 10. A human eye74is self explanatory. This is the best view in which to discuss the means for securely fastening the horizontal-guide31to the vertical-guide32. Four front-lugs41are provided integral to the horizontal-guide31flush with the back side of the horizontal-guide31. These lugs align with four back-lugs42provided integral to the vertical-guide32which are flush with the front side of the vertical-guide32. All four pairs of lugs are fastened together with sufficient structural integrity with four sets of bolt and nut lug-fasteners43. A forehead-rest96(FIG. 15) is shown broken away. A full view of it is shown inFIG. 15. Refer toFIG. 7andFIG. 8for a description of other referenced components.

FIG. 10is an orthographic back view of the preferred embodiment. This shows the gear teeth of the vertical-pinion71engaging both the right-vertical-rack35and the left-vertical-rack36gear teeth. It is so open and accessible that a transparent-gear-cover73(invisible in this view) is provided to prevent a patient's hair from getting tangled in the gears. The transparent-gear-cover73has a height and width matching the vertical-guide32and is secured in place with fasteners75. The forehead-rest96is not shown so that the relationship between the pinion71and the two racks35and36can be clearly shown. The horizontal-guide31is shown behind the vertical-guide32. The vertical-pinion71is shown held in place on the vertical pinion-axle55by the locknut72.

FIG. 11illustrates the bottom view of the preferred embodiment, employing the principles of the present invention. Refer toFIG. 7andFIG. 8for a complete description of the components referenced, except the forehead-rest96is not referenced inFIG. 7andFIG. 8. SeeFIG. 15for a complete description of the forehead-rest96.

FIG. 12Illustrates a partial section view taken throughFIG. 7. Components of particular interest in this view are the right-vertical-T-shaped-groove82and the left-vertical-T-shaped-groove83in which the right-vertical-rack35and the left-vertical-rack36respectively slide up and down in the vertical-guide32in opposite directions as the vertical-adjustment-knob49is rotated clockwise and counterclockwise. Due to the connection of the vertical-adjustment-knob49to the vertical-pinion71through the vertical-pinion-axle55, the rotational movement of the vertical-pinion71mimics the rotation of the vertical-adjustment-knob49. The vertical-pinion-axle55passes through the second-central-hole90, the second-slip-fit-hole93and the second-non-round-hole92in the vertical-pinion71. The vertical-pinion71is held in its proper place by the locknut72.

FIG. 13illustrates a partial side view taken fromFIG. 9. Components of particular interest in this partial view are the ones interconnecting the horizontal-adjustment-knob50with the sliding movement of the bottom-horizontal-rack33and the top-horizontal-rack34within the bottom-horizontal-T-shaped-groove80and the top-horizontal-T-shaped groove81, both within the horizontal-guide31. The horizontal-pinion-axle56passes through the first-central-hole89in the center of the horizontal-adjustment-knob50and is prevented from rotating within the first-central-hole89by the first-set-screw84(hidden in this view). The horizontal-pinion-axle56continues on through the first-slip-fit-hole76in the bearing-plate86and on through the first-non-round-hole91in the horizontal-pinion70and terminating in the bearing-hole88. The locknut72holds the horizontal-pinion70in its proper place. Refer toFIG. 7andFIG. 8for a complete description of other components referenced.

LikewiseFIG. 14illustrates how a left-lens-blank-axis22of a left-lens-blank17is below a left-frame-visual-axis15by a left-vertical-distance26and the left-lens-blank-axis22is to the right of the left-frame-visual-axis15by a left-horizontal-distance28as determined by the same eye exam.

It can now be seen that with this prescription, a commercially available edging machine can be used to grind the right-lens-blank16to fit a right-lens-cut-line20and the left-lens-blank17to fit a left-lens-cut-line19so both lenses can be mounted in eyeglass-frames18for use by a Diplopic patient for improved reading ability.

FIG. 15illustrates the forehead-rest96that steadies the embodiment in relation to the patient's eyes74. It is attached with adhesive to the transparent gear-cover73(hidden by the left-vertical-rod38). The forehead-rest96is positioned and fixedly attached to the patient side of the apparatus to press against the patient's forehead when the eyes align with the centers of a pair of plano lenses having crosshairs wherein the forehead-rest96is constructed of a soft spongy material covered with soft vinyl.

FIG. 16illustrates a rigid adjustable eyeglass frame (Front View, Side View and partial enlarged view) for holding stationary-lenses98for patients who require a negative (−) lens in addition to a prism lens to obtain the necessary magnification for the intended purpose. The eyeglass-frame105has on each end a PD-millimeter-scale104ranging from approximately 25 mm to 35 mm to accommodate most PDs. A rigid integral central-extension106extends upward to the level of a horizontal-slot97at which point a rigid integral horizontal-fitting107is sized to snuggly fit into the horizontal-slot97located near the bottom of the Vertical-guide32(doctor's side). The lens98is held in front of the patient's eye by a lens-holder99that has a groove that snuggly fits the lens with sufficient tension to prevent the lens falling out. Integral to the lens-holder99is a rigid extension100that projects outward away from the patient and then vertically to an integral sleeve102that freely slides along the eyeglass-frame105, when a thumbscrew108is loose. The sleeve102has a window101on the doctor's side that allows full view of a sufficient portion of the PDmillimeter-scale104. The sleeve102has a PD-index103at the bottom edge of the eyeglass-frame105for the purpose of aligning the PD index103with the appropriate PD on the PD-milllimeter-scale at which time the thumbscrew108is tightened.

FIG. 17is an enlarged view of the OD lens holder showing, in detail, the radial scale divided into two degree increments. A simple eye test can reveal the “angle” of the displacement of images seen by a Diplopic patient. The angle for the OS will be 180 degrees from the OD angle. This allows the doctor to insert a decentered lens into the lens-holder62and rotate it until the black index is aligned with the angle found (black number) by the eye test. If no such black angle exists on the OD-scale109then rotate the lens until the green index on the lens aligns with the angle that is identified with green numbers. Mathematically add the H & V components (based on the angle) of the decentered lens to the H & V components found by the horizontal-scale48and vertical-scale47according to the User-instructions44printed on the vertical-guide32after the Rx has been fine tuned using the horizontal-adjustment-knob50and vertical-adjustment-knob49controls. With these combined H & V values an Rx can be calculated and written in whatever notation is desired for the OD. Ultimately the OS will have values equal to but opposite the H & V values of the OD.

FIG. 18is an enlarged view of the OS lens holder showing, in detail, the radial scale divided into two degree increments. Based on information already known (fromFIG. 17above) the doctor can insert a decentered lens into the lens-holder63and rotate it until the black index is aligned with the angle found (black number) by the eye test. If no such black angle exists on the OS-scale110then rotate the lens until the green index on the lens aligns with the angle that is identified with green numbers. Mathematically add the H & V components (based on the angle) of the decentered lens to the H & V components found by the horizontal-scale48and vertical-scale47according to the User-instructions44printed on the vertical-guide32after the Rx has been fine tuned using the horizontal-adjustment-knob50and vertical-adjustment-knob49controls. With these combined H & V values an Rx can be calculated and written in whatever notation is desired for the OS.

The foregoing merely illustrates the principles of the invention. For example, although the means for positioning the lens in front of the patient's eyes in the illustrated embodiment are rack and pinion gears, other means are possible such as threaded screws or servo motors. The millimeter scales could be a different unit. The circular scales and the indexes on round knobs could be changed to linear scales affixed to the racks with single indexes affixed to the vertical guide and the horizontal guide. The sliding fit of the four rod bushings could be replaced with linear-ball bearings.

It will thus be appreciated that those skilled in the art will be able to devise numerous alternative arrangements that, while not shown or described herein, employ the principles of the invention and thus are within its spirit and scope.