Abstract:
Devices, systems and methods for scaling the size and/or position of a marker on a magnified image of an object. In preferred embodiments, the object is an eye that is undergoing laser eye surgery. The eye is viewed through a magnification system or microscope and an image of the eye is presented on a display. One or more markers are present on the image, each identifying a specific target location or landmark on the eye. When a desired magnification setting is selected, the image is scaled accordingly. In addition, one or more of the markers is scaled in size and/or position to reflect the magnification setting. This allows the marker to maintain identification of the target location while reflecting the selected magnification level.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application is a Continuation of U.S. application Ser. No. 10/703,195 filed Nov. 5, 2003. The full disclosure of which is incorporated herein by reference in its entirety for all purposes. 
     
    
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    NOT APPLICABLE 
       REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK. 
       [0003]    NOT APPLICABLE 
       BACKGROUND OF THE INVENTION 
       [0004]    The present invention is generally related to magnification systems, particularly sensing magnification settings for use in a visual display of the magnified image, especially for use in laser eye surgery systems. 
         [0005]    Laser eye surgery is performed by a laser after optically aligning the laser with the eye using a magnification system or microscope. While it may be possible to make use of lasers having other wavelengths, known laser eye surgery procedures generally include an ultra-violet or modified frequency infrared laser to remove a microscopic layer of stromal tissue from the eye&#39;s cornea to change the cornea&#39;s contour for varying purposes, such as for correcting myopia, hyperopia, astigmatism and the like. Laser ablation results in photodecomposition of the corneal tissue, but generally does not cause significant thermal damage to adjacent and underlying tissues of the eye. The irradiated molecules are broken into smaller volatile fragments photochemically, directly breaking the intermolecular bonds. 
         [0006]    Most laser eye systems include a microscope to aid the surgeon in aligning the patient&#39;s cornea with the laser system, and to allow the surgeon to optically monitor or verify that the targeted portion of the stroma is removed as intended. Generally, the surgeon observes the patient&#39;s eye at low magnification to orient the procedure and at progressively higher magnification to provide great resolution for finer and more accurate procedures. Known laser eye surgery systems have generally included fairly standard microscope structures. The microscope optics are typically designed to provide flat field, anastigmatic, achromatic, nearly diffraction limited imaging with optical magnification zoomable approximately over a 15-fold range of, say 15×-200×. The magnification is adjustable and is typically selected to correspond to the largest magnification which can still be comfortably used for situating a lesion (that is, the smallest field of view which can be used when magnified across the fixed display size of the video monitor). For example, for corneal refractive surgery, where the surgeon needs to observe the cornea from limbus to limbus, this corresponds to a field of view of approximately 12 to 14 mm. At the screen, the zoom optics allow for adjustable magnification in the range of about 15×-200×, for example. This enables the surgeon to view a very narrow field, on the order of a millimeter in width, or a much wider field at lesser magnification. This is useful in enabling the surgeon to assure himself that he is aimed and focused at a particular desired region. 
         [0007]    The ability to track or follow movements of a patient&#39;s eye is recognized as a desirable feature in laser eye surgery systems. Movements of the eye include both voluntary movements and involuntary movements. In other words, even when the patient is holding “steady” fixation on a visual target, eye movement still occurs. Tracking of the eye during laser eye surgery has been proposed to avoid uncomfortable structures which attempt to achieve total immobilization of the eye. Tracking by following the subject eye tissue, i.e., recognizing new locations of the same tissue and readjusting the imaging system and the surgical laser aim to the new location, assures that the laser, when firing through a prescribed pattern, will not deviate from the pattern an unacceptable distance. Sometimes this distance is held within  5  pm throughout ophthalmic surgery, which sets a margin of error for the procedure. However, either more stringent or alternatively more lax displacement error tolerances may be desirable to improve overall system performance. 
         [0008]    Typically at the start of the procedure, the target region of the eye is aligned with a marker, such as a fixed reticle, visible through the microscope. In some laser eye surgery systems, an image of the target region and the fixed reticle as seen through the microscope is displayed on a system monitor for viewing by the surgeon. As the eye moves during the procedure, the target region deviates in relation to the fixed reticle. To identify the target tissue and its position in relation to the fixed reticle, another marker, such as a moving cross-hair, is provided in the monitor display which indicates the tracked target tissue. Both the fixed reticle and the moving cross-hair are visible on the display unless the eye moves excessively, outside of the range of the microscope. This typically indicates that the eye is beyond the tracking range and the ablation pattern has been interrupted until the eye returns to a position within acceptable range. Thus, the reticle and cross-hair allow the surgeon to observe the eye movements of the patient throughout the procedure and identify any excessive movements of the eye. 
         [0009]    When the surgeon changes the magnification setting of the microscope, the image of the eye displayed on the monitor is scaled accordingly. It would be desirable to provide appropriately scaled and positioned markers at any magnification setting to maintain relational information for the viewer. Such systems should be adaptable to existing laser eye surgery systems, easy to use and cost effective. At least some of these objectives will be met by the inventions described hereinafter. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    The present invention provides devices, systems and methods for scaling the size and/or position of a marker on a magnified image of an object. In preferred embodiments, the object is an eye that is undergoing laser eye surgery. The eye is viewed through a magnification system or microscope and an image of the eye is presented on a display. One or more markers are present on the image, each identifying a specific target location or landmark on the eye. When a desired magnification setting is selected, the image is scaled accordingly. In addition, one or more of the markers is scaled in size and/or position to reflect the magnification setting. This allows the marker to maintain identification of the target location while reflecting the selected magnification level. 
         [0011]    In a first aspect, the present invention provides a system for scaling the size and/or position of a marker on a magnified image of an object. In preferred embodiments, the system includes a magnification system that magnifies a view of the object. The magnification system includes a magnification selector that selects a magnification level for viewing of the object upon actuation, wherein selecting comprises changing from a first magnification level to a second magnification level. Thus, the magnification selector may be comprised of a knob, button, lever, switch or other mechanism which is used to select a desired magnification level. Actuation of the magnification selector changes the magnification level to the desired or selected magnification level. It may be appreciated that the magnification level may be any level from zero to any maximum level. A zero magnification level would provide an image as seen in plain view, without magnification. Thus, the magnification selector can change the magnification between plain view and magnified view and between various degrees of magnification. Example magnification levels include 1.0, 0.63, 1.6, 2.5 and 4.0. In preferred embodiments, the magnification system also includes a magnification sensor system which senses the selected magnification level. The sensor system is used to scale and position the markers as will be described in later sections. 
         [0012]    The markers may be any of any form and may be used to convey any information to the viewer. As mentioned, in preferred embodiments, each of the markers identifies on the image a specific target location or landmark of the eye. For example, a target location or landmark may be a pupil, particularly the center of the pupil. This target location is particularly useful when tracking an eye for laser eye surgery. Often, the center of the pupil is aligned with a fixed marker, for example a fixed reticle, at the start of a surgical procedure. As the eye moves during the procedure, the pupil center deviates in relation to the fixed reticle. To identify the center of the pupil as it moves and its position in relation to the fixed reticle, another marker, such as a moving cross-hair, is provided on the image which indicates the tracked pupil center. Thus, in some embodiments, the system includes a tracking system capable of tracking a target location on the object. 
         [0013]    The system also includes system software which provides an image of the object at the selected magnification level and a marker, such as a cross-hair, positioned on the target location of the image as the location is tracked by the tracking system. The software adjusts the position of the cross-hair based on the sensed magnification level to maintain positioning on the target location of the image when changing magnification levels. Thus, when the magnification system is set at a first magnification level, the marker is seen by the viewer on the target location of the image. When the magnification level is changed, the target location on the image may move on the display, such as along an x-axis or y-axis, due to zooming effects. The system software ensures that the cross-hair maintains positioning on the target location by an adjustment in positioning itself. 
         [0014]    In some embodiments, the system software further adjusts the size of the cross-hair based on the sensed magnification level to maintain size relationship between the cross-hair and the image of the object when changing magnification levels. Thus, when increasing the magnification level, the cross-hair is increased in size proportionally to the magnification level and, likewise, when decreasing the magnification level, the cross-hair is proportionally decreased in size. 
         [0015]    In addition, in some embodiments, the system software further provides another marker, such as a fixed reticle, which has a center indicating a reference position for the target location. The software may adjust the size of at least the center of the fixed reticle based on the sensed magnification level to maintain size relationship between the center of the fixed reticle and the image of the object when changing magnification levels. Thus, the cross-hair and the fixed reticle may be of the same size or differing sizes. But, in either case, each or both of the markers may be scaled with the magnification level. 
         [0016]    As mentioned, the magnification system also includes a magnification sensor system which senses the selected magnification level. The sensor system is used to scale and position the markers. In preferred embodiments, the magnification sensor system generates a gray scale code which signifies the selected magnification level. The magnification sensor system may include a gray scale encoder and at least one opto-sensor which is able to sense a portion of the encoder to generate the gray scale code. The gray scale encoder may have the shape of a wheel wherein the portion sensed by the opto-sensors is a lip which protrudes around a portion of the wheel. The gray scale encoder wheel is rotated by selection of the magnification level, such as by rotation of a knob which selects a magnification level at each rotation stop or detent. At each rotation stop, the opto-sensors each sense the presence or absence of the lip of the gray scale encoder. The presence of the lip encodes a “1” and the absence of the lip encodes a “0”. Together, the codes from the opto-sensors generates a gray scale code. In preferred embodiments, the at least one opto-sensor comprises three opto-sensors which together generate the gray scale code. Rotation of the wheel to the next rotation stop rotates the lip, thereby generating a different gray scale code. In some embodiments, three opto-sensors generate gray scale codes corresponding to six magnification levels or rotation stops. 
         [0017]    In a second aspect, the present invention provides a method for scaling the size and/or position of a marker on a magnified image of an object. In preferred embodiments, the method includes providing a magnification system which magnifies a view of an object to a desired magnification level upon selection of the desired magnification level. The method also includes selecting the desired magnification level by actuating a magnification selector which changes the view from an existing magnification level to the selected magnification level, the selecting step actuating a magnification sensor which senses the selected magnification level. Typically, the method also includes tracking a target location on the object with a tracking system. An image of the object is then viewed at the selected magnification level and a marker positioned on the target location of the image as the location is tracked by the tracking system, wherein the position of the marker has been adjusted based on the sensed magnification level to maintain positioning on the target location of the image when changing from the existing magnification level to the selected magnification level. 
         [0018]    In some embodiments, the size of the marker has additionally been adjusted based on the sensed magnification level to maintain size relationship between the marker and the image of the object when changing from the existing magnification level to the selected magnification level. 
         [0019]    In additional embodiments, the viewing step further includes viewing an additional marker, such as a fixed reticle, having a center indicating a reference position for the target location, wherein the size of at least the center of the fixed reticle has been adjusted based on the sensed magnification level to maintain size relationship between the at least the center of the fixed reticle and the image of the object when changing from the existing magnification level to the selected magnification level. It may be appreciated that the markers may each be of the same or different size at a selected magnification level. And, the magnification levels may be of any magnification, including zero magnification or plain view. 
         [0020]    When the magnification system comprises a microscope adapted for use in laser eye surgery, the object is a patient&#39;s eye. Thus, the method may also include ablating the patient&#39;s eye with the use of a laser eye surgery system while viewing the image of the eye. The patient&#39;s eye includes a pupil having a center, and typically the target location for placement of a marker is the pupil center on the image. In this case the viewing step may further include viewing the marker, such as a cross-hair, on the pupil center of the image of the patient&#39;s eye. Thus, as the pupil center moves and is tracked by the tracking system, the viewer may follow the tracked movements of the pupil center by watching the moving cross-hair on the visual display. 
         [0021]    Actuation of the magnification sensor generates a gray scale code which signifies the selected magnification level. In preferred embodiments, selecting the desired magnification level manipulates a gray scale encoder so that at least one opto-sensor changes its ability to sense a portion of the encoder which generates the gray scale code. Manipulation of the gray scale encoder may include rotation of the gray scale encoder, such as by a knob which is used to change the magnification level. The method may further include selecting another desired magnification level by actuating the magnification selector. This in turn would generate another gray scale code by the magnification sensor. In some embodiments, the method includes selecting up to six desired magnification levels by actuating the magnification selector. The generated gray scale codes used to scale and position the markers as described above. 
         [0022]    Other objects and advantages of the present invention will become apparent from the detailed description to follow, together with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a laser eye surgery system of the present invention including a magnification system through which an eye of a patient is viewed. 
           [0024]      FIGS. 2A-2C  illustrate a display showing images of the patient&#39;s eye and at least one marker. 
           [0025]      FIG. 3  provides a schematic illustration of a portion of the microscope of the laser eye surgery system. 
           [0026]      FIG. 4  provides a table of magnification settings. 
           [0027]      FIG. 5  illustrates an embodiment of the magnification setting sensor system. 
           [0028]      FIG. 6  provides a table of pin-outs for a DB9M connection. 
           [0029]      FIG. 7  illustrates a gray scale encoder engaged with a PCB. 
           [0030]      FIG. 8  provides a table which shows the detent positions of the knob with corresponding detent degree positions, corresponding gray scale codes and corresponding magnification settings. 
           [0031]      FIGS. 9A-9D  illustrate the generation of the gray scale code by the magnification setting sensor system. 
           [0032]      FIG. 10  illustrates the sensor system disposed in the microscope body. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Referring now to  FIG. 1 , an embodiment of a laser eye surgery system  10  of the present invention includes a magnification system or microscope  12  through which an eye E of a patient is viewed, typically while the eye E is ablated by a laser beam  14 . In preferred embodiments, the microscope  12  comprises a Leica MS5 microscope, however any suitable microscope or microscope components may be used. The eye E may be viewed by a surgeon through eyepieces  18  on the microscope  12 . The microscope  12  includes, among other components, knobs  22  for adjusting the magnification of the microscope  12 . Thus, by rotation of the knobs  22 , the eye E may be viewed under varying levels of magnification through the eyepieces  18 . In addition, laser eye surgery system  10  of the present invention includes a monitor display  16  which provides an image  20  of the eye E as viewed through the eye pieces  18 . This allows the surgeon and any other assistants or practitioners to easily view the eye E throughout the surgical procedure without approaching the eyepieces  18  of the microscope  12 . The display  16  may also provide additional information related to the procedure and provide a user interface with the use of a keyboard  24  for user input. 
         [0034]    The image  20  of the eye E may include a pupil image  30  having a pupil/iris boundary  32 , an iris image  34  having a limbus  36 , and a sclera image  37  as shown on the display  16  of  FIG. 1 . At the start of the surgical procedure, the eye E is aligned with the desired path of the laser beam  14  by centering a target tissue area of the eye E with the center of a fixed reticle  40 . The fixed reticle  40  may be viewed through the eyepieces  18  and is also projected into the image  20  for viewing on the display  16 . In this example, the pupil image  30  is centered to be aligned with the center of the fixed reticle  40 . 
         [0035]      FIG. 2A  provides a closer view of the display  16  of  FIG. 1  having the pupil image  30  aligned with the center of the fixed reticle  40 . As mentioned, the eye E typically moves both voluntarily and involuntarily while the eye E is generally aligned. Such movement is tracked by an eye tracker. Tracking by following the subject eye tissue, i.e., recognizing new locations of the same tissue and readjusting the imaging system and the surgical laser aim to the new location, assures that the laser, when firing through a prescribed ablation pattern, will not deviate from the pattern an unacceptable distance.  FIG. 2B  illustrates the eye E having moved away from its previous position during tracking. Software included in the system  10  projects onto the display  16  a moving cross-hair  42  which tracks the previously centered eye tissue (in this case the center of the pupil). As shown, the moving cross-hair  42  may be displaced from the fixed reticle center  40  by an x-distance  44  along an x-axis and a y-distance  46  along a perpendicular y-axis. In addition, the moving cross-hair  42  may rotate in relation to the fixed reticle center  40 , as shown. 
         [0036]    By rotation of the knobs  22 , the eye E may be viewed under varying levels of magnification. As the magnification level is changed, the image  20  on the display  16  is appropriately scaled to show the image  20  at the new magnification level. In addition, the fixed reticle  40  and the moving cross-hair  42  are also scaled in size and position to reflect the new magnification level.  FIG. 2C  illustrates the image  20  of  FIG. 2B  at a higher level of magnification. As shown, the size of the reticle  40  and cross-hair  42  are appropriately larger and the cross-hair  42  is displaced by x′-distance  50  along the x-axis and y′-distance  48  along the perpendicular y-axis, wherein x′ and y′ are scaled to reflect the magnification level. Thus, the cross-hair  42  maintains representation of tracking the previously centered eye tissue (in this case the center of the pupil). Such rescaling is achieved with software of the laser eye surgery system  10 . 
         [0037]      FIG. 3  provides a schematic illustration of a portion of the microscope  12  of the laser eye surgery system  10 . This portion includes a microscope body  60  having a microscope top  62 . Viewholes  64  are visible through the microscope top  62  which allow viewing through the eyepieces (not shown) and the microscope body  60 . In addition, the portion includes knobs  22  for adjusting the magnification level. Typically, a magnification setting indicator  66  is present to display the magnification level. In this illustration, an indicator  66  is positioned near the rotating knob  22  displaying the level “2.5”. It may be appreciated that the indicator  66  may be present at any location(s) including the display  16 . The Leica MS5 microscope has six magnification position settings. The six positions are continuous wherein the magnification knob has no 360 degree rotation stops, the knob  22  rotated beyond 360 degrees repeats the six magnification settings. Table 1 provided in  FIG. 4  shows the possible magnification settings of this embodiment. 
         [0038]    The present invention includes a magnification setting sensor system which informs the laser eye surgery system software of the magnification setting.  FIG. 5  illustrates an embodiment of the magnification setting sensor system  70 . The sensor system  70  comprises a magnification sensor body  72  including at least one opto-sensor, in this embodiment three opt-sensors (S 0 , S 1 , S 2 ) are present. The opto-sensors S 0 , S 1 , S 2  are disposed on a Printed Circuit Board (PCB)  80  with a cable connection to the rear of the magnification sensor body  72 . The cable connection is DB9M; the pin-outs for the DB9M connection are presented in Table 2 of  FIG. 6 . The sensor system  70  also includes a gray scale encoder  74 . The encoder  74  is positioned between the magnification sensor body  72  and the knob  22 . The encoder  74  and knob  22  are attached to a knob shaft  76  so that rotation of the knob  22  rotates the encoder  74  in addition to rotating a magnification carousel  78  which provides lenses to magnify the viewed object, in this case the eye E. 
         [0039]      FIG. 7  illustrates the gray scale encoder  74  engaged with the PCB  80 . As shown, the opto-sensors S 0 , S 1 , S 2  are shaped to extend over a lip  82  on the encoder  74 . When the encoder  74  is rotated through the magnification settings or rotation stops by rotation of the knob  22 , the lip  82  is also rotated through the rotation stops. Since the lip  82  extends only along a portion of the encoder  74 , in this embodiment along 180 degrees of the encoder  74 , the presence of the lip  82  is sensed by the sensors S 0 , S 1 , S 2  as the encoder  74  is rotated in either the clockwise or counter-clockwise direction. Sensing of the presence of the lip  82  of the gray scale encoder  74  provides a gray scale code which indicates the rotation stop that the knob  22  has been turned to, which in turn indicates the magnification setting of the microscope. The gray scale code is a variation of the standard binary code in which only one bit changes at a time between successive binary digits.  FIG. 8  provides Table 3 which shows the detent positions of the knob  22  with corresponding detent degree positions, corresponding gray scale codes and corresponding magnification settings. 
         [0040]      FIGS. 9A-9D  further illustrate the generation of the gray scale code by the magnification setting sensor system  70 .  FIG. 9A  illustrates the view from the PCB circuit side looking through the PCB back at the gray scale encoder. In this embodiment, the opto-sensors S 0 , S 1 , S 2  are disposed at the 30, 90, 150 degree positions respectively. The opto- sensors remain stationary as the gray scale encoder rotates.  FIG. 9A  also illustrates the locations of the six detents disposed 60 degrees apart, at 0, 60, 120, 180, 240 and 300 degrees.  FIGS. 9B-9D  illustrate the movement of the lip  82  (indicated by shading) as the gray scale encoder  74  is rotated through the detents.  FIG. 9B  illustrates the encoder  74  at the first detent wherein the lip  82  is sensed by all three opto-sensors S 0 , S 1 , S 2 . This provides a gray scale code of  111 . The gray scale code is transmitted from the PCB  80  to the system controller of the laser eye surgery system  10 . The system controller software determines if valid magnification position settings are being sent from the PCB  80 . Referring to Table 3 of  FIG. 8 , a gray scale code of  111  corresponds to a magnification setting of 1.0. Thus, the system software appropriately scales the size and position of the reticle  40  and cross-hair  42  on the image  20 , as described and illustrated in  FIGS. 2A-2C , to reflect the magnification setting of 1.0. In addition, the system software may display the sensed magnification setting. 
         [0041]      FIG. 9C  illustrates rotation of the encoder  74  counter clockwise (CCW) to the second detent wherein the lip  82  is rotated so that the lip  82  is sensed by opto-sensors S 1 , S 2 . This provides a gray scale code of  110 . Referring to Table 3 of  FIG. 8 , a gray scale code of  110  corresponds to a magnification setting of 0.63. Thus, the system software appropriately scales the size and position of the reticle  40  and cross-hair  42  on the image  20 , as described and illustrated in  FIGS. 2A-2C , to reflect the magnification setting of 0.63. In addition, the system software may display the sensed magnification setting. 
         [0042]      FIG. 9D  illustrates rotation of the encoder  74  counter clockwise (CCW) to the third detent wherein the lip  82  is rotated so that the lip  82  is sensed by opto-sensor S 2 . This provides a gray scale code of  100 . Referring to Table 3 of  FIG. 8 , a gray scale code of  100  corresponds to a magnification setting of 1.6. Thus, the system software appropriately scales the size and position of the reticle  40  and cross-hair  42  on the image  20 , as described and illustrated in  FIGS. 2A-2C , to reflect the magnification setting of 1.6. In addition, the system software may display the sensed magnification setting. It may be appreciated that rotation of the encoder  74  through the remaining detent positions will continue rotating the lip  82  and providing gray scale codes in the same manner. In this way, the magnification settings are transmitted through the system software to be used in conjunction with the display. 
         [0043]    The magnification setting sensor system  70  is a compact system which is easily incorporated into existing microscopes. As shown in  FIG. 10 , the sensor system  70  is disposed within the microscope body  60 , between the magnification carousel  78  and the knob  22 . Thus, the knob  22  and magnification setting indicator  66  may appear identical to a standard microscope so that the magnification setting sensor system  70  is an unobtrusive addition to the laser eye surgery system  10 . 
         [0044]    Although the foregoing invention has been described in some detail by way of illustration and example, for purposes of clarity of understanding, it will be obvious that various alternatives, modifications and equivalents may be used and the above description should not be taken as limiting in scope of the invention which is defined by the appended claims.