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1. WO2004002381 - LASER VISION CORRECTION APPARATUS AND CONTROL METHOD

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[ EN ]

LASER VISION CORRECTION APPARATUS AND CONTROL METHOD

BACKGROUND OF THE INVENTION
Field of the Invention
The invention is generally directed to the field of laser vision correction, and more particularly, to laser vision correction systems and control apparatus and methods.

Description of Related Art
Ultraviolet laser systems and related methods are known for enabling ophthalmic surgery on the cornea in order to correct vision defects. Techniques for ablative photodecomposition include, but are not limited to, LASH , LASEK, and PRK.
Conventional treatment by these techniques is typically indicated for refractive defects including myopia, hyperopia, and presbyopia, with or without astigmatism. In some cases, re-treatment from a previous surgery is also indicated.
Although surgeons administer the ophthalmic treatment, it is typically the laser manufacturers who program their lasers with tissue ablation algorithms to effect suitable treatment for the various diagnosed refractive defects. As used herein, the term "tissue ablation algorithm" refers to the process or procedure carried out in and by the hardware/software of the laser system. As illustrated schematically by the laser system 10 in Figure 1, some type of diagnostic input 12 from a surgeon and/or one or more diagnostic devices 14 is sent to a laser platform 16. The laser platform includes a computer-linked control system 18 that utilizes software to compute an appropriate laser ablation shot file based upon optical zone size and other input parameters entered by the surgeon. The laser platform also includes hardware in the form of beam shaping and steering optics that react to instructions from the control system to deliver the shot file in the appropriate manner to the cornea. Thus, the laser platform is a "smart" device, so to speak, because it is there that both information processing and treatment execution occur. In an aspect shown by the dotted lines, the laser platform is capable of receiving a computer-readable medium 20 having both enablement and instructional software stored therein which can be processed by the computer system in the laser platform.
Certain disadvantages attach to the methodologies such as those described above. In the first case described, the laser platform is burdened with computer hardware and software adding to the complexity and cost of every unit. In the second scenario described above, the computer-readable medium may be in the form of a single use enablement card, for example, as described in U.S. Patent Nos. 6,296,634 and 6,364,873. Such enablement cards are typically purchased by a user, and generate a set per-procedure fee for the laser manufacturer. Each treatment procedure requires a card, while the laser system continues to require the necessary computer hardware and software as mentioned above. Thus the laser system lacks flexibility and is no less burdened than described above. Moreover, there are many aspects of the laser platform that can malfunction, increasing the risk of surgical downtime for the user. Trained technicians having skills in multiple technical fields are required to maintain and service the multi-component laser platforms.
In view of the foregoing and other disadvantages currently associated with typical laser vision correction systems, the inventors have recognized a need for improvements that increase the flexibility and reduce the cost of making, supplying, mamtaining, and controlling laser vision correction systems, and which make it easier for the surgeon to provide the best treatment outcomes for their patients.

SUMMARY OF THE INVENTION
The invention is generally directed to apparatus and methods involved in the control of a laser vision correction system, and a system incorporating these controls.
An embodiment of the invention is directed to a device-readable medium on or in which is stored a pre-programmed, readable, first corrective instruction reference. This instruction reference corresponds to an encoded customized corrective instruction. As used herein, the term "customized corrective instruction" refers to the number, sequence, and placement of laser pulses for a particular laser vision correction treatment. The • instruction is determined by a calculation module located external to the medium and to the laser platform, and is executable by the laser platform of a laser vision correction system. The customized corrective instruction is determined in a manner that will be described in greater detail below. A particular customized corrective instruction is then encoded in such a manner that the instruction can be executed by the laser platform upon recognition of the corresponding instruction reference stored in or on the medium. In an aspect of this embodiment, the first corrective instruction reference stored in or on the medium is a necessary and sufficient component for enabling the laser platform to execute the customized instruction when the instruction reference is. properly recognized. In an alternative aspect, the first instruction reference is a necessary but not sufficient component for allowing enablement and execution of the customized instruction by the laser platform. Rather, a second, readable corrective instruction reference is stored in or on the medium and in combination with the first corrective instruction reference, is sufficient for enabling execution of the customized instruction. Preferably, the second instruction reference will correspond to an encoded user ID or laser platform ID which will be associated with the customized instruction. In an alternative aspect, the medium may have stored therein a second pre-programmed instruction reference and a third preprogrammed instruction reference, corresponding to a user ID and a laser platform LD, in addition to the first instruction reference corresponding to the customized corrective instruction. In this aspect, all three matching instruction references are necessary and, in combination, sufficient components for enabling the execution of the customized instruction by the laser platform. With respect to all of the aspects referred to above, the total data storage requirement for any or all of the instruction references in combination, along with any other information stored in the medium, preferably will not exceed 1000 bytes of storage space. In another aspect according to this embodiment, the medium includes a laser platform disablement feature that limits a preset number of uses of the laser platform for each readable medium unit. This feature provides an annuity structure for laser system use as is well known in the art. In a further aspect, the medium includes a beam sizing and shaping feature to provide a desired beam diameter and beam energy profile for ablating a corneal surface and or facilitating beam diagnostics.
In another embodiment according to the invention, a laser vision correction system includes a calculation module that can receive input data relating at least to a refractive defect of a patient's eye and calculate a customized corrective instruction based, at least in part, upon the input data. As used herein, the term calculation module refers either to a hardware device, computer-executable software which performs all pertinent aspects of an ablation treatment algorithm, or a combination of hardware, software, and/or firmware for determining the customized corrective instruction. The calculated customized corrective instruction is then encoded such that the encryption will allow a matching correspondence to a pre-programmed first corrective instruction reference that is stored in or on a device-readable medium. The system further includes a laser platform that can receive the readable medium and execute the customized corrective instruction, as a necessary condition, only when the first corrective instruction reference corresponding to the encoded customized corrective, instruction is recognized by the laser platform. The calculation module is external, to the laser platform and preferably resides in a diagnostic platform that is used to generate at least some of the input data. In a preferred aspect of this embodiment, the customized corrective instruction calculated by the calculation module may include more than one particular corrective instruction for each of a variety of laser vision corrective treatments. For example, depending upon the input data, the calculation module may generate three different corrective instructions for myopia treatments, or, two different instructions for hyperopia treatments, that, when encoded, correspond to the first corrective instruction reference on the storage medium, thus potentially providing the user with a choice of appropriate treatment options. In a related aspect, the system includes a graphical user interface (GUI) that is operably associated with the laser platform, along with a configuration file that is also operably associated with the laser platform and the GUI. In this aspect, the configuration file will recognize the instruction reference corresponding to the customized corrective instruction and will then initiate a particular GUI associated with the one or more matched, customized corrective instructions. The GUI will then allow the user to input information that will result in the selection of a single matching instruction reference recognized by the configuration file in the laser platform that will enable and allow the laser platform to execute the particular customized refractive instruction.
In another embodiment, a method for controlling a laser vision correction system includes providing a device-readable medium having the attributes of the device-readable medium set forth hereinabove, for use in a laser platform to execute a particular laser vision correction procedure. It further includes providing the medium to a third party on a remunerative basis; and, structuring the remuneration as a function of type and or number of corresponding instruction references supplied in the medium.
Another method embodiment for controlling a laser vision correction system involves determining a customized corrective instruction for correcting an ophthalmic refractive defect, encoding the instruction, providing a transferable device-readable medium that includes a pre-programmed, first corrective instruction reference which corresponds to the encoded instruction, and providing a laser platform that can receive the transferable medium and recognize the corresponding first instruction reference as a necessary condition for enabling execution of the customized corrective instruction. In a preferred aspect, the method further includes providing a GUI that is operably connected with the laser platform and which is configured according to the instruction reference corresponding to the encoded instruction. In a further related aspect, the method includes providing either or both of an encoded user LD and an encoded laser platform ID, and providing associated second and/or third corresponding instruction references in the transferable medium which are recognizable as necessary arid, perhaps, sufficient conditions for allowing execution of the customized corrective instruction. In addition to, or in place of, the second and/or third instruction reference, other corresponding codes can be stored in the medium; e.g., iris pattern codes. The medium storage structure may further be writeable such that the medium could be inserted into a component of the diagnostic platform to directly receive specific encoded or uncoded data.

BRIEF DESCRIPTION OF THE DRAWINGS .
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings,
Figure 1 is a block diagram of a prior art laser vision correction system;
Figure 2 is a block diagram of a laser vision correction system according to an embodiment of the invention;
Figure 3 is a block diagram of a more detailed illustration of the system of Figure 2;
Figure 4 is a front view line drawing of a device-readable enablement medium according to a preferred embodiment of the invention;
Figure 5 is a drawing showing a beam shaping feature of the enablement medium according to a preferred embodiment of the invention;
Figure 6 is a more detailed illustration of the beam shaping feature of the enablement medium according to an embodiment of the invention;

Figure 7 is a graphical illustration of a laser beam intensity profile produced by the beam shaping feature of the enablement medium according to an embodiment of the invention; and
Figure 8 is a front view illustration of an alignment and positioning apparatus for the enablement medium according to an embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Figure 2 shows a simplified block diagram of a laser vision correction system 100 according to a preferred embodiment of the invention. The basic components of the system include a calculation module 150, a laser platform 102, and a device readable medium 134 that is transferable to and readable by the laser platform 102. The readable medium 134 is preferably in the form of a card similar in size and shape to a credit card. The card medium 134 includes a section 133 for storing data that can be read by an appropriate card reader 130 located in the laser platform 102.
The calculation module 150 receives input data 151 from what is referred to as a diagnostic platform 105. The diagnostic platform 105 can be comprised of a single diagnostic instrument that provides diagnostic information relating to a patient's refractive defect, or any combination of various diagnostic instruments and/or other forms of outcome influencing information that a surgeon may wish to enter. In a preferred embodiment, the calculation module 150 is an executable computer software routine that runs in a diagnostic wavefront sensing device 105. Wavefront measurement information is fed into the calculation module 150 which then uses that information to calculate one or more appropriate laser treatments. These treatments are referred to herein as customized corrective instructions 120. These instructions ultimately instruct a fire control system (not shown) in the laser platform 102 where to direct a series of laser pulses on the patient' s cornea to effect the appropriate laser vision correction treatment.
In order to control the enablement and use of the laser platform 102 for the delivery of a customized corrective instruction 120, a device-readable medium 134 as preferably illustrated in Figure 4, is utilized. The medium 134 includes a data storage section 133 that is preprogrammed with a first corrective instruction reference 132. The-first corrective instruction reference 132 will match an encryption code 120'-corresponding to a customized corrective instruction 120 generated by the calculation module 150 based upon the input data 151. The laser platform 102 is equipped with a device-readable medium reader 130 which acts in one capacity as a lock and key mechanism, so to speak. Thus, when the readable medium 134 is inserted into and read by the reader 130, a necessary condition enabling the laser platform 102 to execute the customized corrective instruction 120 will be a recognition of the first corrective instruction reference 132 corresponding to the encoded customized corrective
instruction 120'. This recognition is preferably accomplished in a configuration file 119 operably associated with, and preferably located in, the laser platform 102. A graphical user interface 144 is operably associated with the laser platform 102 arid the configuration file 119 to further enable execution of the customized corrective instruction 120, as will be discussed in greater detail below.
A further illustration of a preferred embodiment of the laser vision correction system 100 is illustrated in Figure 3 and is described as follows. Ultimately, a laser vision correction treatment 190 in the form of a programmed series of ablating laser pulses will be directed to a patient's eye 192 to reshape the cornea in an attempt to correct a refractive defect of the patient's eye. Laser vision corrective surgery is typically provided, or being developed for, myopia, hyperopia, presbyopia, retreatment, customized treatment, and other conditions, as appreciated by those skilled in the art. The
determination of a particular refractive defect starts with diagnostic information about the patient's eye and its visual quality. This diagnostic input data 151 can be generated by one or more diagnostic devices including wavefront sensors, topography devices, ultrasonic pachymeters, optical coherence tomography (OCT) devices, refractometersj slit lamp ophthalmoscopes (SLOs), iris pattern recognition apparatus, and others, for example, well appreciated by those skilled in the art, and by other pertinent information that may be supplied by the practitioner including surgical environmental conditions, " particular patient data, surgeon factors, and others. As used herein, the diagnostic platform 105, not a part of the invention per se, is used to collectively refer to any or all of the appropriate means for providing diagnostic information indicative of the patient's refractive defect. The appropriate input data 151 is fed to a calculation module 150. Preferably, the calculation module 150 comprises software that uses the input data 151 to determine one or more of an appropriate myopia treatment (MYn), hyperopia treatment (HYP„), presbyopia treatment (PBYn), etc., 120 as shown. As an illustrative example, a Zywave® wavefront sensor (Bausch & Lomb Incorporated, Rochester, New York) includes a computer that runs software known in the industry as Zylink® ablation computation software. Zylink uses the wavefront diagnostic data to determine an appropriate shot file for execution by a laser platform such as a Technolas 217Z® laser. Despite the fact that most ablation algorithms are determined by the laser manufacturers, surgeons constantly develop personalized nomograms based upon relevant outcome influencing factors which they have determined optimize their treatment outcomes. For example, a surgeon in Hong Kong may modify the calculated treatment to the extent permitted with a customized nomogram that produces optimized myopic correction for Asian patients. Similarly, for example, a surgeon in Florida may obtain optimized surgical outcomes using a different myopia treatment nomogram that compensates for humidity effects on outcome. Thus the calculation module 150 may calculate one myopia treatment (MYi) based upon a particular set of input data, and a different customized myopia treatment (MY2) based upon a different set of input data. Likewise, one or more hyperopia treatments, presbyopic treatments, retreatments, customized treatments, or other treatments can be determined b'y-the calculation module. These are listed as HYPi, HYP2 ..., MYi, MY2 ..., PBYj, PBY2 ..., etc., in the Figure 3. Each of these calculated treatments becomes a customized corrective instruction 120 that is executable by an enabled laser platform 102 upon appropriate command. Advantageously, via the invention, the laser platform 102 has become a "dumb black box," so to speak, because the instruction for execution by the laser platform has been calculated externally of the laser platform.
With further reference to Figure 4, the device-readable medium 134 has a data storage section 133 in or on which is pre-programmed the first corrective instruction reference 132. The first corrective instruction reference 132 corresponds to one or more of the encoded customized corrective instructions 120' determined by the calculation module 150. The data storage section 133 of the card medium 134 preferably has a data storage capacity of 1000 bytes or less making the card medium a relatively simple and inexpensive component suitable for single or pre-set limited use. The laser platform 102 is equipped with a card reader 130. The laser platform 102 further includes a
configuration file 119. The configuration file 119 is preferably a hardware file that is adapted to recognize the instruction reference 132 on the card medium 134 corresponding to the encoded customized correction instruction 120'. Recognition of the first
instruction reference by the configuration file 119 is a necessary condition for enabling the laser platform 102 to execute the predetermined customized corrective instruction 120. In a simple illustration, the calculation module 150 will generate a single myopia ablation "■ treatment 120 based upon particular input data 151. The user of the laser system will then need a card medium 134 that has a first instruction reference 132 stored therein which corresponds-to the code 120' associated with the customized corrective " "'■■""" instruction 120. Use of the card medium in the laser platform and recognition of the corresponding instruction reference by the configuration file will unlock the laser platform for use and will enable the laser platform to carry out the particular customized corrective instruction 120.
Laser corrective surgery typically requires specific input from the surgeon; for example, the size of the optical zone (OZ) which is related to the depth of ablation for a particular treatment and further which is a determining factor as to whether a particular treatment can safely be carried out. This type of information is usually input into the system by the surgeon via a keypad 141 and a graphical user interface (GUI) 144 associated with the laser platform 102. According to a preferred aspect of the invention, the configuration file 1.19, upon recognition of a first corrective instruction reference 132 corresponding to an encoded customized corrective instruction 120', will call up an appropriate graphical user interface 144 which will allow the surgeon to input or confirm any deterministic data for the treatment. Thus, a customized corrective instruction for a myopia treatment may generate a different graphical user interface screen than a customized corrective instruction for a hyperopia treatment, and so on. In any event, it is a necessary condition for operation of the laser platform that the first instruction reference 132 match the customized corrective instruction code 120'. Preferably, at least one second instruction reference 123 stored in the card medium 134 will match a second code 123' and this will be a necessary and sufficient condition for enabling the laser platform 102 to execute the instruction 120. For example, the second instruction reference 123 may necessarily have to match a user LD code along with the matching first instruction reference 132 in order to unlock and enable the laser platform. More preferably, a third instruction reference 125 stored in the card medium 134 must necessarily match a laser platform LD such that only all three matching instruction references 132, 123, 125 are necessary and sufficient conditions for enabling the laser platform. In this manner, only an identified user may use an identified laser platform to carry out a particular customized corrective instruction. Other second, third, and/or more instruction references may be stored in the card medium. For example, an instruction reference may correspond to an iris pattern code, or to an encoded LASLK flap thickness measurement. In the latter case, for example, a microkeratome platform may be adapted to accept the card medium and write to the storage section a lamellar code indicative of or relating to flap thickness. When the card medium is then engaged with the laser platform, recognition of a particular lamellar code may be a necessary condition for enabling the laser platform.

In another preferred aspect of the invention as shown in Figure 4, the card medium 134 will be equipped with a laser platform disablement feature 135. The disablement feature 135 can be an electronic circuit or other well-known means that can be configured in such a manner to preset the number of uses of the card medium to enable the laser platform. Preferably, each card medium 134 could be preset to disable the laser platform after each single use. Alternatively, the card medium 134 could be programmed for two uses per card in the form of a single use on each eye of the patient. A new card medium will be required for each use of the laser, thus setting up an annuity structure for the card provider.
With further reference to Figure 4, another preferred aspect of the invention shows the card medium 134 with one or more apertures 304, 302, 307, in an aperture mask 311. Each aperture shapes and/or characterizes the laser beam passing through the aperture on its way to the target surface. In a preferred aspect illustrated with reference to Figure 6, one of the apertures 304, referred to herein as a "soft-spot" aperture, has a central, directly transmitting aperture portion 305 surrounded by a plurality of smaller, diffracting apertures 306. The directly transmitting portion 305 of the aperture 304 essentially determines a beam spot diameter, while the diffractively transmitting portion 306 generates a particular beam energy profile which, in an exemplary case, is a soft-spot profile. Figure 7 illustrates a soft-spot profile 400 which has the form of a truncated Gaussian distribution. Preferably, the directly transmitting portion 305 of aperture 304 has a diameter of 3 mm for directly transmitting the laser beam upon proper alignment, producing a 2mm beam diameter spot on the target surface. Another aperture 307 is also a soft-spot aperture, preferably having a directly transmitting portion diameter of about 1.5mm and delivering a 1mm beam on target. Aperture 302 contains only a . directly transmitting portion used for beam fluence calibration. Thus, the card medium 134 preferably has two soft-spot apertures 304, 307 of different overall diameters, and a hard spot aperture 302, as shown in. Figure 5. Upon proper alignment and positioning of . the card medium 134 in the laser beam path of the module 102, two different beam spot sizes can selectively be projected onto the exposed cornea surface. Preferably, the two spot sizes on the corneal surface will be 2mm and 1mm. An automatic, pressure based mechanism 300, as illustrated in Figure 8, is used to position and align the card 134 in the laser beam path in the module 102. Fixation points 222χ,y and pressure points 224x,y are used as follows: the fixation points 222^ comprise three hardened cylinder pins that are press fit with high accuracy into a card holder 226. The card 134 is pushed into the holder 226 from right to left (as viewed in Figure 7) until the left edge 227 of the card touches fixation point 222x and the bottom edge 229 of the card touches fixation points. 222yι and 222y2. The card is fixated against the fixation points by pressure points 224x, 224y which, preferably, are springs. By manufacturing the card 134 with high precision such that the exact location of the apertures are known, and the fixation points engage the card edges at the same locations, repeated-positioning of the cards has shown a measured accuracy of ±5 μm or better. The interested reader is further referred to U.S. Patent Nos. 6,090,100; 5,683,379; 5,827,264; 5,891,132, all of which are herein incorporated by reference in their entirety to the extent allowed by applicable laws and rules.
Referring again to Figure 7, a preferable truncated Gaussian ablation profile (or spatial intensity distribution) 400 passed by the 3mm soft-spot aperture 304, is shown. Ln the figure, the profile is normalized and only one-half the profile 400 is illustrated, solely for simplicity of the drawing, it being understood that the full profile 400 would be as if mirrored about the ordinate axis of Figure 7. The 1mm aperture 307 would pass a similar, but narrower, profile. As can be seen, a center portion 401 of the aperture profile 400 is flat or substantially flat, whereas an edge 402 of the profile 400 is continuous with the portion 401 and is rounded. The portion 401 is preferably symmetric about the radius of the profile and extends across about 60-80%, and, more preferably, across about 65-70% of the profile 400. At a certain point, such as an intensity threshold point 404 at which the eye tissue ablation intensity threshold is no longer reached, the -profile 400 .. preferably quickly drops off or diminishes as a substantially square, vertical, or truncated . edge 406. The ablation threshold and any variations in it are known in the art. The. amount of energy falling below the threshold for ablation is preferably about 5% or less of the total energy encompassed by the profile 400.
The apparatus embodiments described herein naturally support method
embodiments according to the invention. A preferred embodiment is a method for controlling a laser vision correction system that involves providing, to a third party, a device-readable medium (134) as set forth hereinabove, for use in a laser platform (102) to enable and execute a particular customized corrective instruction. Since provision of . the Card medium forms the basis of an annuity model for the card medium provider (typically the laser manufacturer), a single or preset use limitation (135) enabled by the card medium (134) promotes business transaction between the card supplier and the laser user. This is commonly referred to as the "per-procedure" model. In an aspect of this embodiment, the remunerative structure may be set according to the type and/or number of customized corrective instructions corresponding to the first instruction reference supplied on a particular card medium. For example, a physician may plan to perform 1,000 myopia laser procedures within a general patient base, and 100 customized myopia procedures within a select patient base. Based upon the input data, the calculation module may generate two different myopia treatment algorithms associated, respectively, with a non-customized myopia treatment and a customized myopia treatment.
Accordingly, a user may purchase 1,000 cards containing a first matching instruction reference that will enable the laser platform to execute only a non-customized myopia treatment at some nominal cost per card unit. Similarly, the user may purchase 100 cards, each of which has a first matching instruction reference that will be recognized to enable the laser platform to execute a customized myopia treatment. These cards will have a different cost per card unit than the non-customized enabling cards. Thus, the
remunerative basis of the card transaction can be structured upon the type of treatment, number of treatments, or other factors enabled by the particular code or codes stored on the card medium.
A related embodiment describes a method for controlling a laser vision correction system that involves generating a customized corrective instruction for correcting an ophthalmic refractive defect based upon diagnostic information indicative of that refractive defect; encoding the customized corrective instruction; providing a transferable, device-readable medium having a storage structure that contains a first corrective instruction reference that corresponds to the encoded customized corrective instruction; and providing, in a laser platform that is adapted to receive the device-readable medium, a means for recognizing the first instruction reference as a necessary condition for enablement and execution of the customized corrective instruction. In a preferred aspect, the recognition means includes a configuration file in the laser platform that upon recognition of the first instruction reference and, optionally, a second and/or third matching instruction reference which correspond to a user ID and/or a laser platform ED, for example, calls up a particular graphical user interface for additional data input by the surgeon. Upon appropriate input, the apparatus described hereinabove will, for example, position the card medium in the laser beam path and deliver a series of desired laser beam pulses to the patient's cornea to effect the desired treatment for correcting or at least improving upon the patient's refractive defect.
Based upon the foregoing, it can be appreciated that the card medium 134 including the first instruction reference 132 has greatly enhanced the flexibility of the vision correction system on several fronts over the prior art technology. Whereas, traditionally, a single enablement-type card was required for each procedure at a set fee per card, unit, according to the invention, a variety of pre-programmed
enablement/instruction cards priced according to card/system enablement features are made available for use in a simplified laser platform.
Notwithstanding the preferred embodiments specifically illustrated and described herein, it will be appreciated that various modifications and variations of the instant invention are possible in light of the description set forth above and the appended claims, without departing from the spirit and scope of the invention.