Abstract:
An ophthalmic marker having a U-shaped yoke ( 33 ) at one end of a cranked axle ( 42 ) is disclosed. The axle ( 42 ) is rotatable mounted with a co-axial cylindrical handle ( 31 ). The other end of the axle extends beyond the handle and is bifurcated. A plumb bob ( 38 ) having a sphere ( 40 ) and a stem ( 39 ) is pivotally mounted on the bifurcated end of the axle ( 42 ). The yoke ( 33 ) has three marker points ( 34 - 36 ) the upper two ( 35, 36 ) of which are maintained in a horizontal plane by a gravitational force urging the plumb bob ( 38 ) into a vertical plane notwithstanding the handle ( 31 ) not being held exactly horizontal. A method of eye marking and marker making are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation-In-Part (CIP) of U.S. patent application Ser. No. 13/002,668 filed Feb. 3, 2011, which is a U.S. National Stage of PCT/AU2009/000756 filed Jun. 16, 2009 which, in turn, claims priority to Australian Application No.: 20080903531 filed Jul. 29, 2008, the entire contents of each which is incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to optical equipment and, in particular, to a marking device used by an ophthalmic surgeon to mark a patient&#39;s eye prior to, for example, intraocular surgery such as cataract surgery. 
     BACKGROUND ART 
     Cataract surgery has been performed for many years. Toric intraocular lenses have been available for many years (StarSurgical/Rayner) but recently Alcon has popularised their use. This lens is particularly useful for patients having astigmatism. Roughly one third of all patients requiring cataract surgery have astigmatism and in order for the intraocular lens to function correctly it must be accurately placed. It is estimated that for every degree of incorrect orientation, the astigmic correction factor for such an intraocular lens decreases by approximately 3%. As a consequence, pre-operative marking is imperative for accurate surgery. 
     However, measurements on the patient&#39;s eye which are conducted pre-operatively are conducted in the consulting rooms of the ophthalmic surgeon where the patient sits upright with his torso in a vertical position. However, when the patient lies down, and is thus supine as required for surgery, the eye rotates by a variable amount which differs considerably from patient to patient. Thus the intention of the marking procedure is to enable the eye to be marked with reference markings which can be used to determine the correct alignment of the intraocular lens, the correct alignment of incisions, etc., during surgery. The marks themselves are made with a dye that is painted onto or otherwise applied to various prongs of the marker and which are accurately pressed onto the eye whilst the patient is seated and thus has his head vertical. 
     There are three basic prior art marking devices. One class of such devices are free hand systems where the marking prongs are located at one end of an elongate stem or pencil like handle which is held by the ophthalmic surgeon. This relies upon the dexterity of the surgeon. There is another device which incorporates a small spirit level into the handle in order to indicate a horizontal plane. There is a third class of markers which incorporate a plumb bob and thus rely upon gravitational forces to maintain the marking device aligned with the vertical. It is with this class of marking devices that the present invention is concerned. The particular prior art device which gave rise to the present invention is manufactured by Rumex of St Petersburg, Fla., USA. 
     In U.S. Pat. No. 8,491,616 Davis an instrument is disclosed in which a weighted stem  60  is connected by a short handle  50  which the medical practitioner holds. As illustrated in  FIG. 9 , the handle  50  is only long enough to be held in the fashion of a tea-cup handle between the thumb and forefinger of the operator. This is a relatively awkward and uncomfortable grip which does not assist in the production of accurate results. 
     In German Utility Model 20 2008 004 59301 a similar arrangement is disclosed with the handle  50  of Davis above being replaced with an axle  14  which is rotatably and transversely mounted at one end of an elongated handle  11 . Thus the handle of the medical practitioner is located on the handle  11  and thus positioned far away from the eye of the patient. As a consequence the fingers of the handle holding the handle can not be used to manipulate the patient&#39;s eyelids, if necessary. 
     Genesis of the Invention 
     The genesis of the present invention is a desire to improve the abovementioned Rumex prior art marking device. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention there is disclosed an ophthalmic marker for marking a patient&#39;s eyeball prior to intraocular surgery, said marker comprising a central longitudinal axle defining a longitudinal axis, said axle being contained within, and rotatable relative to, an elongate substantially co-axial and substantially cylindrical body constituting a handle able to be grasped in the manner of a pencil, one end of said axle extending beyond said body and terminating in an optical marker means, and the other end of said axle extending beyond said body and terminating in a plumb bob, said plumb bob being interconnected to said axle to apply a gravitational torque thereto. 
     In accordance with a second aspect of the present invention there is disclosed a method of making a marker to mark a patient&#39;s eyeball prior to intraocular surgery, said method comprising the steps of:
         (i) locating at least two marker points one at each opposite end of a substantially U-shaped yoke,   (ii) locating said yoke at one end of an axle,   (iii) rotatably mounting said axle within a substantially co-axial hollow handle, the other end of said axle extending beyond said handle, and   (iv) connecting a plumb bob to said handle to apply a gravitational torque thereto.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is front elevational view of a patient&#39;s eye with the patient vertical and showing the desired location of three marks, 
         FIG. 2  is a horizontal cross-section to enlarged scale showing the patient&#39;s cornea and the marks A and B of  FIG. 1 , 
         FIG. 3  is a perspective view of a prior art ophthalmic marking device, 
         FIG. 4  is a perspective view of the ophthalmic marker of the preferred embodiment being held in the right hand of an ophthalmic surgeon, 
         FIG. 5  is a perspective view of the rear end of the ophthalmic marker of  FIG. 4 , and 
         FIG. 6  is a perspective view looking towards this right of the U-shaped yoke of the ophthalmic marking device of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     As seen in  FIG. 1 , prior to carrying out ophthalmic surgery, the eye  2  is required to be marked in order to enable the ophthalmic surgeon to identify the centre (or axis or front) of the eye when the patient is upright. As seen in  FIG. 1  three points are preferably marked which in relation to the globe of the earth are as follows:
         A: is on the equator, but at 90° west of the Greenwich meridian,   B: is also on the equator but 90° east of the Greenwich meridian, and   C: is on the Greenwich meridian but a latitude corresponding to the South Atlantic.       

     The points A and B are also illustrated in  FIG. 2  which is a cross-sectional view taken along the line A-B of  FIG. 1  and thus passes through the centre of the cornea  4 . 
     The prior art marking device able to mark the points A and B (only) of  FIG. 1  is illustrated in  FIG. 3 . The prior art device  10  has a pencil like handle  11  having a knurled portion  12  which enables the handle  11  to be conveniently held like a pencil by the hand of the ophthalmic surgeon. 
     At the front of the device  10  is a U-shaped yoke  13  having two points  15 ,  16  to which a dye can be applied and which when placed on the eyeball  3  create the marks A and B. The yoke  13  is connected to the handle  11  by means of a curved rod  17  which is rotatably mounted within the handle  11 . A plumb bob  18  having a rigid stem  19  and a sphere  20 , is rigidly connected to the rod  17 . 
     In operation the device  10  is held with the handle  11  in a substantially horizontal plane opposite the patient&#39;s eye  2 . The weight of the plumb bob  18  ensures that the rod  17  is rotated by the plumb bob  18 . Thus the plumb bob  18  is vertical and so the yoke  13  (which is perpendicular to the stem  19 ) is horizontal. Thus provided the ophthalmic surgeon keeps the handle  11  in a substantially horizontal plane, the ophthalmic surgeon can judge the centre (or axis or front) of the eye and then bring the points  15  and  16  into contact with the eyeball  3  and thereby make the marks A and B simultaneously and reasonably accurately. 
     This arrangement suffers from three difficulties. The first is that the ophthalmic surgeon must keep the handle  11  substantially horizontal in order to ensure that the rod  17  can rotate under the influence of the plumb bob  18 . In addition, the fingers of the ophthalmic surgeon are not able to be moved any further forwardly along the device  10  than the knurled portion  12  since the fingers must not interfere with the swinging operation of the plumb bob  18 . As a consequence, the ophthalmic surgeon has only his other hand with which to control the patient&#39;s eye lids and so this is generally of inconvenience to the ophthalmic surgeon. Thirdly, the plumb bob  18  must not come into contact with the patient lest its vertical position be disturbed, thereby moving the pointers  15 ,  16  away from the horizontal. 
     Turning now to  FIGS. 4 to 6 , the ophthalmic marker  30  of the preferred embodiment has an elongate handle  31  with a ribbed portion  32  constituting a finger grip. A U-shaped yoke  33  is provided but is orientated into the vertical plane and has three points  34 ,  35  and  36  respectively which protrude perpendicularly from the plane of the yoke  33 . The yoke  33  is connected by means of a cranked portion  37  to an axle  42  which extends the length of the elongate handle  31 . The axle  42  is rotatably mounted relative to the elongate handle  31  so as to be substantially co-axial therewith and to be a smooth substantially frictionless rotational fit within the handle  31 . 
     As best seen in  FIG. 5 , the rear end of the axle  42  is bifurcated at  44  and the rigid stem  39  of a plumb bob  38  (including a sphere  40 ) is pivoted by means of a pin  45  which extends through the bifurcated portion  44  of the axle  42 . As also seen in  FIG. 5 , the axle  42  is supported by a bearing plate  47  and is conveniently visible through an aperture  49  in the handle  31 . 
     Since the axle  42  is rotatably mounted, the weight of the plumb bob  38  with its sphere  40  maintains the U-shaped yoke  33  with its points  35  and  36  uppermost and level (ie horizontal), irrespective of any twisting action of the handle  31  relative to the axle  42 . Thus no matter how the ophthalmic surgeon either deliberately or inadvertently rotates the elongate handle  31  relative to the axle  42 , the axle  42  always remains stationery with the stem  39  vertical and thus the points  35  and  36  horizontal. 
     Furthermore, the elongate handle  31  can be tilted in a vertical plane through a wide range of degrees and the plumb bob  38  remains vertical since the stem  39  is able to pivot about the pin  45 . Therefore it is not necessary for the ophthalmic surgeon to keep the handle  31  in a substantially horizontal plane as is the case with the handle  11  of the prior art device  10 . 
     As a consequence of these mechanical improvements, the marker  30  is much more convenient for the ophthalmic surgeon to use. In particular, the forefinger and middle finger of the hand holding the marker  30  are available to assist in maintaining the patient&#39;s eye lids retracted and steady the hand, if necessary, thereby enabling the ophthalmic surgeon to use more than one hand in carrying out the marking procedure. 
     In addition, the additional point  34  enables the mark C as illustrated in Fig . 1  to be made, thereby improving the definition of the optical axes for the surgeon. 
     Still further, the elongate handle  31  is able to be held by the surgeon in the same manner as one holds a new pencil or pen. This grip is comfortable and much more relaxed for the surgeon than the awkward tea-cup holder posture of Davis. As best seen in  FIG. 4 , the length of the handle  31  extends from in front of the tip of the surgeon&#39;s thumb and forefinger to well behind the upper surface of the surgeon&#39;s hand (that is the surface of the hand opposite to the palm). 
     The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the ophthalmic arts, can be made thereto without departing from the scope of the present invention. 
     The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of”.