Patent Application
20120016349
The present invention relates to ophthalmic laser surgery and, more particularly, an ophthalmic interface apparatus used to stabilize the eye of a patient with respect to a laser beam during ophthalmic surgery and system and method of interfacing the eye with a surgical laser.
In recent years, significant developments in laser technology have led to its application in the field of ophthalmic surgery. In particular, laser surgery has become the technique of choice for ophthalmic surgical applications. In certain ophthalmic laser procedures, surgeons use a mechanical device termed a microkeratome to cut a layer of the anterior surface of the cornea in order to expose the underlying corneal stroma to which the laser is applied. However, complications surrounding the use of the microkeratome with a metal blade have resulted in research into improved techniques that are performed exclusively by a laser system. Such all-laser techniques provide significant improvements over conventional mechanical devices.
Despite these advances in laser technology, the use of such systems for ophthalmic surgical procedures remains fraught with substantial mechanical limitations, particularly in the area of developing a stable interface between an incident laser beam and the eye of a patient. Ophthalmic surgery is a precision operation and requires precise coupling between the surgical tool (i.e., the laser beam) and the region to be disturbed (i.e., a portion of the patient's eye). Movement of the eye with respect to the intended focal point of the laser beam can lead to non-optimal results and might result in permanent damage to non-renewable tissue within the eye. Given that eye movement is often the result of autonomic reflex, techniques have been developed in an attempt to stabilize the position of a patient's eye with respect to an incident laser beam.
One technique used to compensate for relative eye motion with respect to an incident laser beam is to have the patient focus on a stationary target. This involves providing a visual target to the eye undergoing surgery, and requiring that the patient retain focused on the perceived target feature. While this technique has provided some benefit, the patient bears a significant burden of minimizing relative motion. This technique is also less tolerant of any significant gross autonomic reflex motions, e.g., as when the patient might be startled. In this technique, the target provides an optical interface, while the patient's conscious responses provide the feedback mechanism.
Another technique involves the use of an optical eye tracking apparatus, whereby a selected eye feature is targeted for monitoring by an optical device. As the targeted feature displaces as a result of eye movement, this displacement is characterized and fed into the incident laser beam control apparatus as a compensation signal. This technique offers a substantial improvement over the first, particularly when implemented in addition to a patient-driven target focusing mechanism. However, such systems are inordinately expensive since a second, completely independent optical path is typically provided between a patient's eye and a surgical apparatus in order to accommodate the eye tracking apparatus. Further expense and complexity is incurred since an eye tracking apparatus requires an additional software component in order to be operative, which software component must be integrated into a laser delivery system. Considerations of interoperability must be met as well as the provision for an automatic shutdown of the laser system in the event of the loss of target feature lock.
Mechanical stabilization devices have been proposed, for example, a corneal applanation device, which is the subject of U.S. patent application Ser. No. 09/172,819, filed Oct. 15, 1998, and commonly owned by the assignee of the present invention. Such a mechanical device directly couples a patient's eye to the laser's delivery system being affixed to both the laser and the anterior surface of a patient's cornea. The corneal coupling, in these devices, is typically implemented by lowering an applanation fixture over the anterior surface of the cornea under pressure. It is assumed in these forms of devices that pressure applied normal to the corneal surface will restrict conventional motion of the cornea thereby stabilizing the eye along a major access normal to the device.
However, although this assumption may hold true in a large number of cases, it certainly does not have universal application. Moreover, in the cases where it does hold, the device/cornea interface should be established with the iris centered, for best results. The actual establishment of an effective device/corneal interface is an exercise in trial-and-error, resulting in a great deal of frustration to doctor and patient, as well as considerable eye fatigue.
For ophthalmic laser procedures where eye tissue is to be photodisrupted, it is desirable to have proper focus of the laser beam to a specific focal spot in the tissue that is to be effected. Proper focus includes focal definition and proper dimensionality (i.e., the correct spot diameter and shape). To this end, it is helpful for the laser beam to be as free from aberrations as possible. In particular, for ophthalmic laser procedures involving the cornea, the spherical geometry of the cornea can introduce optical aberrations by its shape, and these are separate and distinct from aberrations that may be introduced by the laser optical system. Corneal induced aberrations can distort the definition of the focal spot of a laser beam as the beam is focused to a position within corneal tissue or deeper into the eye, such as the capsular bag or the natural lens.
Due to the spherical geometry of the anterior surface of the cornea, two specific types of aberrations are of particular importance with regard to beam distortion; spherical aberration (which relates to points on the optical axis of the laser beam) and coma which relates to points that are off-axis). Spherical aberration and coma are similar to one another in that they both arise from a failure to image or focus optical ray traces onto the same point. Spherical aberration relates to a distortion that can be characterized as radial in nature, with some radial directions being stretched while other radial directions are shrunk, converting thereby, an ideally circular spot into an elliptical spot. Coma distortion, on the other hand, implies an elongation along one radius a circle, resulting in a “comet-like” shape. Accordingly, any structure which interfaces between a curved, anterior surface of the cornea and laser delivery system will likely encounter such aberration concerns.
In view of the foregoing, it is thus evident that there is a need for a simple mechanical interface device that is able to stabilize the eye against relative motion with respect to a laser beam used for ophthalmic surgical procedures without relying on secondary mechanical considerations, such as surface tension, friction, or the like. Such a device should be able to present an optical feature to an incident laser beam in a stable, well characterized location. In addition to maintaining a proper orientation between the eye and a laser delivery system during ophthalmic laser surgery, such a device should minimize intraocular pressure during the surgical procedure. Such a device should be easy for a clinician to affix, as well as being simple and cost effective to manufacture and use.
Apparatus and methods are provided for interfacing a surgical laser with an eye. In one embodiment, a patient interface device is provided that minimizes aberrations through a combination of a contact lens surface positioning and a liquid medium between an anterior surface of the eye and the contact lens surface. In one embodiment, an interface for coupling a patient's eye to a surgical laser system includes an attachment ring configured to overlay the anterior surface of the eye, a lens cone defining a first plane surface and configured to couple to a delivery tip of the surgical laser such that the delivery tip is positionally referenced to the first plane surface, a gripper, and a chamber configured to receive a liquid. The lens cone includes an apex ring coupled to the first plane surface and an applanation lens disposed at a distal end of the apex ring and positioned in a second plane surface parallel to the first plane surface such that the delivery tip is positionally referenced to the second plane. The gripper includes a first receptacle configured to receive the attachment ring, a central orifice configured to receive the lens cone, a gripper portion, and a receiver portion, and the gripper stabilizes the relative positions of the lens cone and the attachment ring when the lens cone and attachment ring are received within the gripper. The chamber is formed by an inner surface of the attachment ring, an inner surface of the gripper portion, an inner surface of the receiver portion, and the applanation lens when the lens cone and attachment ring are received within the gripper.
In another embodiment, an interface for coupling a patient's eye to a surgical laser system includes an attachment ring configured to overlay an anterior surface of the eye, a lens cone defining a first plane surface and configured to couple to a delivery tip of the surgical laser system such that the delivery tip is positionally referenced to the first plane surface, a gripper, and a chamber configured to receive a liquid. The lens cone includes an apex ring coupled to the first plane surface, and an applanation lens disposed at a distal end of the apex ring. The gripper includes a receptacle receiving the attachment ring, a central orifice receiving the lens cone, a gripper portion, a pair of expandable jaws, and a pair of opposed lever handles coupled to the jaws. The jaws are configured to expand a diameter of the central orifice when opened and further configured to contract the diameter of the central orifice when allowed to relax. The gripper stabilizes the relative positions of the lens cone and the attachment ring when the cone and ring are received within the gripper. The lever handles are configured to apply an opening pressure to the jaws when the opposed handles are squeezed together. The chamber is formed by an inner surface of the attachment ring, an inner surface of the gripper portion, an inner surface of the jaws, and the applanation lens.
In another embodiment, a method for interfacing an eye to a surgical laser is provided including coupling a lens cone to a delivery tip of the surgical laser, coupling an attachment ring to an anterior surface of the eye, receiving a liquid into the first receptacle, positioning the lens cone in a central orifice of a gripper, and stabilizing the relative positions of the lens cone and the attachment ring with the gripper when the lens cone and attachment ring are received within the gripper. The lens cone defines a first plane surface, and the delivery tip is positionally referenced to the first plane surface. The lens cone includes an apex ring coupled to the first plane surface and an applanation lens disposed at a distal end of the apex ring and positioned in a second plane surface parallel to the first plane surface such that the delivery tip is positionally referenced to the second plane. The anterior surface of the eye and an inner surface of the attachment ring form a first receptacle. The gripper includes a second receptacle configured to receive the attachment ring, and the central orifice is configured to receive the lens cone. A chamber containing the liquid is formed by the first receptacle and the applanation lens when the lens cone and attachment ring are received within the gripper.
These and other features, aspects and advantages of the present invention will be more fully understood when considered in connection with the following specification, appended claims and accompanying drawings wherein:
Conceptually, the present invention is directed to a mechanical apparatus that performs the functions of coupling the anterior surface of a target eye to a surgical laser and stabilizing the eye. The apparatus is termed mechanical because it directly couples the mechanical surface of an operative target, such as human corneal tissue, to a mechanical fixture of a surgical laser system, such as the distal tip of a laser beam's delivery system. Simply put, and in the context of a particular embodiment which will be described in greater detail below, the apparatus is affixed to the anterior surface of a human eye and is affixed to the laser delivery system.
Referring initially to the exemplary embodiment of
With regard to the exemplary embodiment of
The component parts of the stabilization device 10 are illustrated in exploded view, and are intended to be collapsed vertically, such that each of the individual portions of the device are in mechanical engagement with appropriate other portions, such that the completed device is provided in a generally unitary structure. This is not to say that the devices' component parts are permanently affixed to one another: indeed, the component parts are separable and interchangeable at will. Rather, the stabilization device 10 is intended to form a single composite interface structure between a human cornea and a surgical laser once the component parts have been aligned with a patient's eye and with respect to the laser delivery system, as will be described in detail below.
As illustrated in the exemplary embodiment of
The attachment ring 12 is disposed and retained within an appropriately shaped female-type receptacle 72 (
The gripper device 14 of the exemplary embodiment of
The receiver portion 20 is disposed below the jaws of the gripper portion 19 and lays in a plane parallel to that of the gripper portion. The receiver portion 20 is cantilevered forward from the space between the lever handles 22 and 24 and the jaws 26 and 27 and is separated from the jaws by a slight spacing. The receiver portion 20 is substantially annular in shape with the central opening 21 extending therethrough. Thus, it will be noted that when the jaws 26 and 27 are opened, only the central opening 21 defined in the gripper portion 19 is widened. The central opening 21 extending through the receiver portion 20 maintains its diameter.
This particular feature allows the attachment ring 12 to be maintained within the central opening 21 of the receiver portion 20, when the jaws 26 and 27 are opened. Likewise, the jaws 26 and 27 may be opened to receive, for example, the lens cone 16, without disturbing or displacing the attachment ring.
In this regard, and in connection with the perspective illustration of
Being cylindrical in construction, the apex ring 30 will be understood to comprise an inner diameter (ID) and an outer diameter (OD), wherein the OD is dimensioned such that it is only slightly larger than the ID of the central opening 21 of the gripper portion 19 of the gripper device 14. The lens cone 16 is constructed of a substantially rigid material such as a rigid, extruded plastic, aluminum, or the like, such that the OD of the apex ring 30 would not be expected to substantially deform under pressure, particularly not under the compression forces applied by the jaws 26 and 27 of the gripper portion 19.
Accordingly, the lens cone 16 would not precisely fit into the ID of the central opening 21 of the gripper device 14 under normal circumstances. However, once compressive force is applied to the lever handles 22 and 24, that force is applied to the remainder of the gripper device 14, causing the jaws 26 and 27 to open and the interior diameter of central opening 21 to increase in consequence. The OD of the apex ring 30 of the lens cone 16 is able to then be inserted into the central opening 21 of the gripper device 14 and, when pressure is released on the lever handles 22 and 24, the jaws 26 and 27 close upon the apex ring 30 thereby grasping the apex ring and establishing a fixed relationship between the lens cone 16 and the gripper device 14. Since the gripper device 14 is in geometric engagement with the attachment ring 12, and since the attachment ring 12 is coupled to corneal tissue, it should be understood that the lens cone 16 is now held in a particular spatial relationship (alignment) with the surface of the cornea.
As will be described in greater detail below, the apex ring 30 defines a receptacle for receiving and retaining an applanation lens 18. The applanation lens 18 is intended to be positioned in proximity with a human cornea and may be used to actually contact the cornea in some embodiments. The gripper device 14 functions to provide an alignment and coupling interface between the lens cone 16, including the applanation lens 18, and the attachment ring 12, and thereby the patient's eye. With regard to the laser delivery system, it will be understood that the base ring portion 28 of the lens cone 16 is adapted to be affixed to the distal end of a laser optical delivery system, such that the delivery system need only be concerned with focusing an incident laser beam at a particular point in space.
In one embodiment, the surface of the applanation lens 18 in contact with corneal tissue (the applanation surface) is disposed at a specific distance from the interface between the base ring and the laser delivery system, such that the anterior corneal surface, or at least that portion in contact with the applanation lens, is at a known specific distance from the laser delivery tip. The surface of the cornea now resides along a plane at a distance known to the laser.
One embodiment of an attachment ring, generally indicated at 12, is illustrated in the cross-sectional diagrams of
The attachment ring 12 further includes an interior, annular ring member 40 which is disposed on and protrudes outwardly from the interior surface of the attachment ring. The annular ring member 40 protrudes outwardly in a direction normal to the interior surface of the attachment ring, on its top surface, but is formed with a bottom surface that includes an upwardly extending cavity 42, with the cavity formed between a bottom portion of the annular ring member 40 and a proximate portion of the interior surface of the attachment ring 12. Thus, it should be understood that the cavity 42 formed by the shape of the annular ring member 40 defines an annular cavity, with its opening pointing towards the bottom, shroud or skirt portion of the attachment ring 12.
In the particular exemplary embodiment of
Additionally, and as best shown in
In operation, and with regard to the particular embodiment of
It should be noted, in connection with the embodiment of
In the embodiment of
Turning now to
As illustrated in the cross-sectional diagram of
Manufacture of the lens cone 16 involves bonding and alignment of the applanation lens 18 to the apex ring 30. Both of these operations (bonding and alignment) are performed at substantially the same time. The lens cone 16 is placed in registration with an alignment and bonding fixture, termed a “golden pedestal”. The golden pedestal has a horizontal alignment plane (an x, y plane) which is positioned parallel to the x, y plane defining the base ring 28. An applanation lens 18 is positioned on the golden pedestal such that its parallel anterior and applanation surfaces lie in the x, y plane defined by the pedestal and, thus the base ring. The lens cone is lowered over the lens until the lens is positioned within the apex ring portion, all the while maintaining the relationship between the various x, y planes. When the lens is in position, it is bonded, with a suitable glue, such as a UV curing cement, to the inside surface of the apex ring, thereby fixing the applanation lens in a specific plane, with respect to the base ring, and at a specific distance from the base ring. Accordingly, it will be appreciated that the applanation lens is established in a specific x, y plane and at a specific z distance from the base ring, itself established in a specific x, y plane and at a specific z distance from the delivery tip of a surgical laser. A known spatial relationship between the laser and the applanation surface of the applanation lens is thereby defined.
The applanation surface provides a reference surface from which the laser system is able to compute a depth of focus characteristic. In embodiments where the applanation surface contacts the corneal surface, since the position of the applanation surface is known, with respect to the delivery tip, so too is the position of the applanated corneal surface. It is, therefore, a relatively straightforward matter to focus a laser beam to any point within the cornea. One needs only to calculate the focal point with respect to the contact surface of the lens, in order that the same focal point be obtained within the eye.
Aligning the lens into position with respect to the lens cone by use of a “golden pedestal” allows alignment tolerances which are substantially tighter than those currently obtainable by conventional microkeratome techniques. Conventional microkeratomes typically exhibit off-plane errors in the range of about +/−30 to +/−40 microns. This alignment error can lead to planar tilt in the corneal flap, and to potential flap thickness variations. For example, if a flap were created with a 30 to 40 micron error, in the positive thickness direction, there exists the possibility that the remaining corneal bed would not be sufficiently thick to conduct a laser ablation procedure. Instead the cornea would tend to bulge outward, in response, leading to a less than optimum surface shape being presented for subsequent laser surface ablation.
In accordance with one embodiment of the invention, the “golden pedestal” registration and alignment system allows for planar (in both the x, y plane and the z direction) alignment tolerances no greater than that of a conventional microkeratome, i.e., in the range of about +/−30 microns, and preferably in the range of about +/−10 microns. This is measured with respect to both the planar “tilt” and the z position of the applanation surface of the applanation lens with respect to the defined plane of the base ring and, therefore, with respect to the laser's delivery tip. This is particularly advantageous when the applanation surface is devised to be co-planar with the anterior surface of the cornea, thereby defining a corneal surface that is mathematically calculable and precise with respect to the laser delivery tip: the x,y plane of the corneal surface is known, and the z distance from the tip to the surface is also known. Thus, a relatively precise cut may be made within the corneal material without concern for depth variation beyond desired pre-determined margins.
In other embodiments, tomography techniques (e.g, optical coherence tomography) or other ranging technology can be used to determine the relative location and position of various ocular structures, including the anterior corneal surface, the various corneal layers (e.g., epithelium, endothelium, Descemet's membrane, stroma, and Bowman's layer), the capsular bag, the lens, the retina, and the like. Using tomography or other ranging techniques, the relative location and position of the laser delivery tip with respect to such structures can be determined and thus, the depth of the laser beam can be determined and calibrated into acceptable tolerances equivalent to the aforementioned tolerances for alignment or tolerances associated with conventional microkeratomes. In such embodiments, the tolerances associated with the dimensions of the lens cone, alignment of the applanation lens, and the like, may have greater acceptable ranges.
Turning now to
In the embodiment shown in
Mechanical pressure of the lens causes the corneal surface to conform to the shape of the applanation surface of the lens. Although depicted in the embodiment of
In one embodiment, the attachment ring 12 is placed around the limbus of the eye, i.e., centered about the cornea and a pupillary aperture. The gripper device 14 has been previously affixed to the attachment ring 12, such that positioning the attachment ring with respect to the eye also positions the eye with respect to the gripper's central opening 21, with the pupillary aperture generally centered within the central opening. Suction is then applied to the attachment ring 12 in order to attach the ring onto the eye. With the eye so presented and held in place by the attachment ring 12, the lens cone 16 and applanation lens 18 can be lowered into proximity or actual contact with the cornea, and retain the lens cone, and particularly the applanation lens, in position by fixing the apex ring 30 with the gripper device 14. The gripper device 14 is opened to receive the lens cone 16 which is then lowered into the attachment ring 12. In one embodiment, the contact surface (applanation surface 66) of the applanation lens 18 can contact the corneal surface thereby applanating the cornea. The gripper device 14 is then closed, thereby clamping the lens cone 16 in position and fixing the applanation lens 18 relative to the cornea. The eye 34 is held to the gripper device 14 by the attachment ring 12, while the applanation lens 18 is held relative to the eye by the gripper device 14.
As should be understood from the foregoing, and with respect to the exemplary embodiments, the stabilization device is substantially rigidly coupled to the laser delivery system, thus the plane of the applanation surface 66 is characterizable in space with respect to any given focal point of an incident laser beam. With regard to the eye, it should be understood that the lens 18 is able to “float” in the “z” direction due to the flexibility of the skirt portion of the attachment ring. The applanation lens 18 is therefore able to accommodate variously shaped corneal surfaces without placing undue pressure on the eye. Although able to “float” in the “z” dimension, the applanation lens 18 is secured against lateral motion and is accurately disposed in a stable “x,y” plane with respect to the eye.
As an alternative embodiment, the applanation lens need not be affixed to the apex ring by a “golden pedestal” approach. As illustrated in the exemplary embodiment of
An additional alternative embodiment will be appreciated by those having skill in the art, when it is considered that the applanation lens 18 might not be affixed to the lens cone 16 prior to the device being assembled on a patient's eye. The applanation lens 18 might be provided as a separate component from the lens cone structure. In this particular embodiment, the applanation lens is constructed as a shallow dish, with sides extending vertically upwards and having an OD such that it may be press-fit within the interior of the annular attachment ring. As the attachment ring and applanation lens combination is fixed to the corneal surface, the applanation lens is able to partially applanate the corneal surface in order to improve alignment. During the initial affixation and alignment procedure, the attachment ring may or may not be fitted within its appropriate receptacle in the gripper device 14. The attachment ring, either with or without the applanation lens included, might be first affixed on the patient's eye and the gripper device 14 lowered over the attachment ring, or, alternatively, the attachment ring, either with or without the applanation lens included, is press fit into its appropriate receptacle on the gripper device 14 and the entire composite placed over the surface of the patient's eye. In this particular instance, care must be taken to precisely manufacture the bottom surface of the apex ring 30, since this is the portion of the lens cone that now contacts the applanation lens 18. Contact pressure between the apex ring 30 and the applanation lens now steadies the lens in the desired plane. Needless to say, the attachment procedures described above hold true for any of the system embodiments described above, as well as one in which the applanation lens 18 is bonded directly to the gripper structure in a suitable position.
After the composite structure is either assembled on the patient's eye, or assembled and then positioned on the patient's eye, the lens cone 16 is lowered into position into the central opening 21 of the gripper device 14 and the jaws 26 and 27 of the gripper device are allowed to relax, thereby grasping and retaining the lens cone in position. As the lens cone 16 is lowered over the structure, final applanation can take place as the applanation lens is either further pressurized against the corneal surface by movement of the lens cone (if the applanation lens is provided as a separate structure) or as the applanation lens is moved into contact with the corneal surface, allowing cone pressure to applanate (if the applanation lens is provided within the lens cone's apex ring). In this regard, it is anticipated that ocular pressure developed by the applanation process will not exceed approximately 60 mmHg, and will preferably be in the range of about 40 to 50 mm Hg.
The lens cone 16 might be secured to the gripper device 14 in a number of ways, in addition to being gripped by compressive jaws. For example, the attachment ring might have a communication channel provided between the suction chamber and its interior surface. Accordingly, as the apex ring of the lens cone is lowered into engagement with the attachment ring, a suction is established between the attachment ring and the lens cone's apex ring thereby securing the lens cone to the attachment ring. Although suction involves a relatively simple application of force between the lens cone and attachment ring, suction (or vacuum) is not the only attachment methodology which is contemplated by practice of the invention. Indeed, the upper portion of the attachment ring might be provided with thin, magnetic material that attracts the lens cone's apex ring and provides for secured docking of the lens cone within the attachment ring. Further, the gripper device 14 might be provided with a suction manifold disposed around the central opening and the apex ring provided with a flange that overlays manifold openings. As the lens cone is lowered into position, and the flange covers the manifold openings, suction is applied thereby securing the lens cone to the gripper device 14. Accordingly, although mating between the lens cone 16 and the gripper device 14 has been described in connection with a flexible, press-fitted attachment, a vacuum attachment or a magnetic attachment, it should be understood that the only requirement is that the lens cone is securely held and maintained in a specific spatial relationship with respect to the attachment ring and, consequently, with the corneal surface.
The present invention has been described, above, primarily with regard to aligning of the structure in relation to a human eye in the “z” dimension, while retaining the eye against relative motion along an “x, y” plane. It is also desirable to ensure proper alignment of the structure with regard to the central access of the eye, i.e., allow the structure to centrate about the pupil, such that the iris/pupil is positioned substantially in the center of the central opening of the attachment ring. Turning now to the semi-schematic, top plan view illustration of
An exemplary embodiment is shown in
Referring to the embodiment shown in
The liquid or otherwise flowable material is preferably biocompatible with the ocular tissue and substantially transparent or has a refractive index that substantially matches the refractive index of the corneal portion 34a. The incorporation of the liquid or otherwise flowable material between the applanation lens 18 and the corneal portion 34a minimizes trajectory departure of the output beam from the laser delivery tip to the desired ocular tissue structure or at least provides relative predictability to determine the trajectory departure, if any. Examples of suitable liquids, fluid-like suspensions or other compositions include but are not necessarily limited to basic salt solution, ophthalmic viscoelastic device, and the like, and any combination of one or more of the foregoing.
The exemplary embodiment shown in
A number of exemplary embodiments suitable for practice of the present invention have been described in connection with various illustrations of
In this particular regard, it will be understood that some degree of spherical aberration might be present in an uncompensated laser beam if the applanation surface of the applanation lens were curved. However, given the mathematical characterizability of the curvature of the applanation surface, it should be understood that a laser beam can be focus-compensated in order to accommodate a degree of curvature.
Accordingly, it is to be understood that the foregoing embodiments are merely illustrative of the invention and that no limitations are intended to either the details of the construction or design other than as defined in the appended claims.
This application is a continuation-in-part application of U.S. patent application Ser. No. 11/948,433, filed Nov. 30, 2007, which is a continuation-in-part application of U.S. patent application Ser. No. 11/277,477, filed Mar. 24, 2006, which is a continuation application of U.S. patent application Ser. No. 10/865,165, filed Jun. 10, 2004, now U.S. Pat. No. 7,018,376, which is a divisional application of U.S. patent application Ser. No. 09/772,539, filed Jan. 29, 2001, now U.S. Pat. No. 6,863,667.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09772539 | Jan 2001 | US |
| Child | 10865165 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10865165 | Jun 2004 | US |
| Child | 11277477 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11948433 | Nov 2007 | US |
| Child | 13230590 | US | |
| Parent | 11277477 | Mar 2006 | US |
| Child | 11948433 | US |
