Patent Application
20140135748
Embodiments of the present invention relate to basis data techniques for use with vision treatment systems and methods. Particular embodiments encompass basis data techniques that account for position-dependent ablation profiles, and that can be used with annular, elliptical, and slit laser beam shapes.
Many current laser correction techniques use small spot scanning systems or broad beam lasers for treating a wide variety of vision conditions, such as myopia and hyperopia. Although these and other proposed treatment devices and methods may provide real benefits to patients in need thereof, still further advances would be desirable. For example, there continues to be a need for improved treatment systems and methods that provide enhanced efficiency. Embodiments of the present invention provide solutions that address certain inefficiencies or shortcomings which may be associated with known techniques, and hence provide answers to at least some of these outstanding needs.
Use of a basis data framework allows the implementation of various ablation profile shapes, which can increase ablation efficiency when treating certain vision conditions. Embodiments of the present invention provide techniques for using elliptical and other ablation profiles during refractive surgery treatment procedures. These techniques can be implemented in a variety of laser devices, including without limitation the WaveScan® System and the STAR S4® Excimer Laser System both by Abbott Medical Optics Inc., the WaveLight® Allegretto Wave® Eye-Q laser, the Schwind Amaris™ lasers, the 217P excimer workstation by Technolas PerfectVision GmbH, the Mel 80™ laser by Carl Zeiss Meditec, Inc., and the like.
With some current vision treatment systems, the time involved for carrying out particular procedures can vary according to the vision condition addressed. As an example, for some laser systems it takes longer to perform a hyperopic treatment than it does to perform a myopic treatment. In instances where the duration of treatment time is excessively lengthy, clinical results may be less than optimal, in part because the eye tissue may undergo substantial dehydration during the course of treatment.
In one aspect, embodiments of the present invention encompass systems and methods for generating a target ablation shape for use in a refractive treatment for an eye of a patient. Exemplary methods may include obtaining a basis data energy profile corresponding to an iris type, determining a pulse ablation profile based on the basis data energy profile and an apodization function, and generating the target ablation shape based on the pulse ablation profile. In some cases, the iris type can be a circular shape, an elliptical shape, an annular shape, or a slit shape. According to some embodiments, methods may also include determining a refractive treatment protocol based on the target ablation shape. In some embodiments, methods may include administering the refractive treatment protocol to the eye of the patient. In some cases, a refractive treatment protocol can include a laser treatment. In some cases, the apodization function can include a Gaussian curve, a normal curve, or a bell curve.
In another aspect, embodiments of the present invention encompass systems for determining an ablation target shape for use in a refractive treatment for an eye of a patient, comprising. An exemplary system may include a processor, a basis data energy profile module, a pulse ablation profile module, and a target ablation shape module. In some cases, the basis data energy profile module can include a tangible medium embodying machine-readable code that is executed on the processor to receive a basis data energy profile corresponding to an iris type. According to some embodiments, the iris type can be a circular shape, an elliptical shape, an annular shape, or a slit shape. In some cases, the pulse ablation profile module includes a tangible medium embodying machine-readable code that is executed on the processor to determine a pulse ablation profile based on the basis data energy profile and an apodization function. In some cases, the target ablation shape module includes a tangible medium embodying machine-readable code that is executed on the processor to generate a target ablation shape based on the pulse ablation profile. According to some embodiments, systems may also include a refractive treatment protocol module having a tangible medium embodying machine-readable code that is executed on the processor to determine a refractive treatment protocol based on the target ablation shape. In some cases, the refractive treatment protocol includes a laser treatment. In some cases, the apodization function can include a Gaussian curve, a normal curve, or a bell curve.
In another aspect, embodiments of the present invention encompass computer products for generating target ablation shapes. For example, a computer product embodied on a tangible computer readable storage medium can include code for receiving a basis data energy profile corresponding to an iris type, code for determining a pulse ablation profile based on the basis data energy profile and an apodization function, and code for generating the target ablation shape based on the pulse ablation profile. In some cases, the iris type can be a circular shape, an elliptical shape, an annular shape, or a slit shape. In some cases, a computer product embodied on a tangible computer readable storage medium can also include code for determining a refractive treatment protocol based on the target ablation shape. In some cases, a computer product embodied on a tangible computer readable storage medium can also include code for administering the refractive treatment protocol to the eye of the patient. In some cases, the refractive treatment protocol can include a laser treatment. In some cases, the apodization function can include a Gaussian curve, a normal curve, or a bell curve.
In still another aspect, embodiments of the present invention encompass systems and methods for generating a target ablation shape for use in a refractive treatment for an eye of a patient. Exemplary methods may include obtaining a basis data energy profile, determining a pulse ablation profile based on the basis data energy profile and an off-axis beam orientation, where the pulse ablation profile has an asymmetric depth profile, and generating the target ablation shape based on the pulse ablation profile. In some cases, methods may include determining a refractive treatment protocol based on the target ablation shape. In some cases, methods can include administering the refractive treatment protocol to the eye of the patient. In some cases, the refractive treatment protocol includes a laser treatment.
In a further aspect, embodiments of the present invention encompass systems for determining an ablation target shape for use in a refractive treatment for an eye of a patient. Exemplary systems can include a processor, a basis data energy profile module, a pulse ablation profile module, and a target ablation shape module. In some cases, a basis data energy profile module can include a tangible medium embodying machine-readable code that is executed on the processor to receive a basis data energy profile. In some cases, a pulse ablation profile module can include a tangible medium embodying machine-readable code that is executed on the processor to determine a pulse ablation profile based on the basis data energy profile and an off-axis beam orientation. The pulse ablation profile can have an asymmetric depth profile. In some cases, a target ablation shape module can include a tangible medium embodying machine-readable code that is executed on the processor to generate a target ablation shape based on the pulse ablation profile. In some cases, a system may also include a refractive treatment protocol module having a tangible medium embodying machine-readable code that is executed on the processor to determine a refractive treatment protocol based on the target ablation shape. In some cases, the refractive treatment protocol includes a laser treatment.
In another aspect, embodiments of the present invention encompass computer products embodied on tangible computer readable storage media having code for receiving a basis data energy profile, code for determining a pulse ablation profile based on the basis data energy profile and an off-axis beam orientation, and code for generating the target ablation shape based on the pulse ablation profile. In some cases, the pulse ablation profile has an asymmetric depth profile. In some cases, a computer product embodied on a tangible computer readable storage medium can also include code for determining a refractive treatment protocol that is based on the target ablation shape. In some cases, a computer product embodied on a tangible computer readable storage medium can also include code for administering the refractive treatment protocol to the eye of the patient. In some cases, the refractive treatment protocol can include a laser treatment.
In yet another aspect, embodiments of the present invention encompass systems and methods for generating a target ablation shape for use in a refractive treatment for a vision condition of an eye of a patient. Exemplary methods can include obtaining a first treatment table based on a first pulse shape and a first error component of the vision condition, obtaining a second treatment table based on a second pulse shape and a second error component of the vision condition, generating a combined treatment table based on the first treatment table and the second treatment table, and generating the target ablation shape based on the combined treatment table. In some cases, the first error component can include a hyperopic component, a cylinder component, or a high order aberration component. In some cases, the first pulse shape can have a circular shape, an annular shape, an elliptical shape, or a slit shape. According to some embodiments, methods may also include determining a refractive treatment protocol based on the target ablation shape. In some cases, methods may also include administering the refractive treatment protocol to the eye of the patient. In some cases, the refractive treatment protocol includes a laser treatment.
In still a further aspect, embodiments of the present invention encompass systems for generating an ablation target shape for use in a refractive treatment for a vision condition of an eye of a patient. Exemplary systems can include a processor, a first treatment table module, a second treatment table module, a combined treatment table module, and a target ablation shape module. In some cases, a first treatment table module can include a tangible medium embodying machine-readable code that is executed on the processor to receive a first treatment table. The first treatment table can be based on a first pulse shape and a first error component of the vision condition. In some cases, a second treatment table module can include a tangible medium embodying machine-readable code that is executed on the processor to receive a second treatment table. The second treatment table can be based on a second pulse shape and a second error component of the vision condition. In some cases, the combined treatment table module can include a tangible medium embodying machine-readable code that is executed on the processor to generate a combined treatment table. The combined treatment table can be based on the first and second treatment tables. In some cases, a target ablation shape module can include a tangible medium embodying machine-readable code that is executed on the processor to generate a target ablation shape based on the combined treatment table. According to some embodiments, systems may also include a refractive treatment protocol module having a tangible medium embodying machine-readable code that is executed on the processor to determine a refractive treatment protocol based on the target ablation shape. In some cases, the refractive treatment protocol can include a laser treatment.
In still yet another aspect, embodiments of the present invention encompass a computer product embodied on a tangible computer readable storage medium, that includes code for receiving a first treatment table, code for receiving a second treatment table, code for generating a combined treatment table, and code for generating a target ablation shape. The first treatment table can be based on a first pulse shape and a first error component of the vision condition. The second treatment table can be based on a second pulse shape and a second error component of the vision condition. The combined treatment table can be based on the first treatment table and the second treatment table. The target ablation shape can be generated based on the combined treatment table. In some cases, a computer product embodied on a tangible computer readable storage medium can also include code for determining a refractive treatment protocol based on the target ablation shape. In some cases, a computer product embodied on a tangible computer readable storage medium can also include code for administering the refractive treatment protocol to the eye of the patient. In some cases, the refractive treatment protocol can include a laser treatment.
In another aspect, embodiments of the present invention encompass systems and methods for generating a target ablation shape for use in a refractive treatment for an eye of a patient. Exemplary methods may include calculating a basis data based on an iris type, and generating the target ablation shape based on the basis data. In some cases, the iris shape can be an elliptical shape, an annular shape, or a slit shape.
In another aspect, embodiments of the present invention encompass systems and methods for generating a target ablation shape for use in a refractive treatment for an eye of a patient. Exemplary methods may include calculating a basis data based on a decentered x-y position of an ablation pulse, and generating the target ablation shape based on the basis data.
For a fuller understanding of the nature and advantages of the present invention, reference should be had to the ensuing detailed description taken in conjunction with the accompanying drawings.
The broad beam top hat laser profile of ablation systems such as the STAR 54® Excimer Laser System by Abbott Medical Optics Inc. is highly effective in ablating myopic shapes, due to the high efficiency of material removal in unit time. It has been discovered that similar efficiencies can be achieved for the ablation of hyperopic shapes. For example reducing the maximum spot size from 6.5 mm to about 4 mm, can effectively reducing the maximum efficiency to 42/6.52=38%. Furthermore, the solution accuracy tolerance, which may be defined as the root mean squares (RMS) error between a target shape and an ablated shape, can involve the use of more small pulses, bringing such an efficiency reduction in practice to the level of nearly 15% for hyperopia. For example, a typical −4 D treatment may involve an ablation of 20 seconds, and a typical +4 treatment may involve an ablation of 120 seconds to ablation, with a 20 Hz laser. The use of other ablation shapes optionally combined with basis data adjustment techniques can improve the treatment time for hyperopia and other vision conditions.
Embodiments of the present invention can be readily adapted for use with existing laser systems and other optical treatment devices. Although system, software, and method embodiments of the present invention are described primarily in the context of a laser eye surgery system, it should be understood that embodiments of the present invention may be adapted for use in alternative eye treatment procedures, systems, or modalities, such as spectacle lenses, intraocular lenses, accommodating IOLs, contact lenses, corneal ring implants, collagenous corneal tissue thermal remodeling, corneal inlays, corneal onlays, other corneal implants or grafts, and the like. Relatedly, systems, software, and methods according to embodiments of the present invention are well suited for customizing any of these treatment modalities to a specific patient. Thus, for example, embodiments encompass custom intraocular lenses, custom contact lenses, custom corneal implants, and the like, which can be configured to treat or ameliorate any of a variety of vision conditions in a particular patient based on their unique ocular characteristics or anatomy. Additionally, the ablation target or target shape may be implemented via other non-ablative laser therapies, such as laser-incised custom lenticule shapes and subsequent extraction and laser-based corneal incision patterns.
Turning now to the drawings,
Laser 12 generally comprises an excimer laser, ideally comprising an argon-fluorine laser producing pulses of laser light having a wavelength of approximately 193 nm. Laser 12 will preferably be designed to provide a feedback stabilized fluence at the patient's eye, delivered via delivery optics 16. The present invention may also be useful with alternative sources of ultraviolet or infrared radiation, particularly those adapted to controllably ablate the corneal tissue without causing significant damage to adjacent and/or underlying tissues of the eye. Such sources include, but are not limited to, solid state lasers and other devices which can generate energy in the ultraviolet wavelength between about 185 and 205 nm and/or those which utilize frequency-multiplying techniques. Hence, although an excimer laser is the illustrative source of an ablating beam, other lasers may be used in the present invention.
Laser system 10 will generally include a computer or programmable processor 22. Processor 22 may comprise (or interface with) a conventional PC system including the standard user interface devices such as a keyboard, a display monitor, and the like. Processor 22 will typically include an input device such as a magnetic or optical disk drive, an internet connection, or the like. Such input devices will often be used to download a computer executable code from a tangible storage media 29 embodying any of the methods of the present invention. Tangible storage media 29 may take the form of a floppy disk, an optical disk, a data tape, a volatile or non-volatile memory, RAM, or the like, and the processor 22 will include the memory boards and other standard components of modern computer systems for storing and executing this code. Tangible storage media 29 may optionally embody wavefront sensor data, wavefront gradients, a wavefront elevation map, a treatment map, a corneal elevation map, and/or an ablation table. While tangible storage media 29 will often be used directly in cooperation with an input device of processor 22, the storage media may also be remotely operatively coupled with processor by means of network connections such as the internet, and by wireless methods such as infrared, Bluetooth, or the like.
Laser 12 and delivery optics 16 will generally direct laser beam 14 to the eye of patient P under the direction of a computer 22. Computer 22 will often selectively adjust laser beam 14 to expose portions of the cornea to the pulses of laser energy so as to effect a predetermined sculpting of the cornea and alter the refractive characteristics of the eye. In many embodiments, both laser beam 14 and the laser delivery optical system 16 will be under computer control of processor 22 to effect the desired laser sculpting process, with the processor effecting (and optionally modifying) the pattern of laser pulses. The pattern of pulses may by summarized in machine readable data of tangible storage media 29 in the form of a treatment table, and the treatment table may be adjusted according to feedback input into processor 22 from an automated image analysis system in response to feedback data provided from an ablation monitoring system feedback system. Optionally, the feedback may be manually entered into the processor by a system operator. Such feedback might be provided by integrating the wavefront measurement system described below with the laser treatment system 10, and processor 22 may continue and/or terminate a sculpting treatment in response to the feedback, and may optionally also modify the planned sculpting based at least in part on the feedback. Measurement systems are further described in U.S. Pat. No. 6,315,413, the full disclosure of which is incorporated herein by reference.
Laser beam 14 may be adjusted to produce the desired sculpting using a variety of alternative mechanisms. The laser beam 14 may be selectively limited using one or more variable apertures. An exemplary variable aperture system having a variable iris and a variable width slit is described in U.S. Pat. No. 5,713,892, the full disclosure of which is incorporated herein by reference. The laser beam may also be tailored by varying the size and offset of the laser spot from an axis of the eye, as described in U.S. Pat. Nos. 5,683,379, 6,203,539, and 6,331,177, the full disclosures of which are incorporated herein by reference.
Still further alternatives are possible, including scanning of the laser beam over the surface of the eye and controlling the number of pulses and/or dwell time at each location, as described, for example, by U.S. Pat. No. 4,665,913, the full disclosure of which is incorporated herein by reference; using masks in the optical path of laser beam 14 which ablate to vary the profile of the beam incident on the cornea, as described in U.S. Pat. No. 5,807,379, the full disclosure of which is incorporated herein by reference; hybrid profile-scanning systems in which a variable size beam (typically controlled by a variable width slit and/or variable diameter iris diaphragm) is scanned across the cornea; or the like. The computer programs and control methodology for these laser pattern tailoring techniques are well described in the patent literature.
Additional components and subsystems may be included with laser system 10, as should be understood by those of skill in the art. For example, spatial and/or temporal integrators may be included to control the distribution of energy within the laser beam, as described in U.S. Pat. No. 5,646,791, the full disclosure of which is incorporated herein by reference. Ablation effluent evacuators/filters, aspirators, and other ancillary components of the laser surgery system are known in the art. Further details of suitable systems for performing a laser ablation procedure can be found in commonly assigned U.S. Pat. Nos. 4,665,913, 4,669,466, 4,732,148, 4,770,172, 4,773,414, 5,207,668, 5,108,388, 5,219,343, 5,646,791 and 5,163,934, the complete disclosures of which are incorporated herein by reference. Suitable systems also include commercially available refractive laser systems such as those manufactured and/or sold by Alcon, Bausch & Lomb, Nidek, WaveLight, LaserSight, Schwind, Zeiss-Meditec, and the like. Basis data can be further characterized for particular lasers or operating conditions, by taking into account localized environmental variables such as temperature, humidity, airflow, and aspiration.
User interface input devices 62 may include a keyboard, pointing devices such as a mouse, trackball, touch pad, or graphics tablet, a scanner, foot pedals, a joystick, a touchscreen incorporated into the display, audio input devices such as voice recognition systems, microphones, and other types of input devices. User input devices 62 will often be used to download a computer executable code from a tangible storage media 29 embodying any of the methods of the present invention. In general, use of the term “input device” is intended to include a variety of conventional and proprietary devices and ways to input information into computer system 22.
User interface output devices 64 may include a display subsystem, a printer, a fax machine, or non-visual displays such as audio output devices. The display subsystem may be a cathode ray tube (CRT), a flat-panel device such as a liquid crystal display (LCD), a projection device, or the like. The display subsystem may also provide a non-visual display such as via audio output devices. In general, use of the term “output device” is intended to include a variety of conventional and proprietary devices and ways to output information from computer system 22 to a user.
Storage subsystem 56 can store the basic programming and data constructs that provide the functionality of the various embodiments of the present invention. For example, a database and modules implementing the functionality of the methods of the present invention, as described herein, may be stored in storage subsystem 56. These software modules are generally executed by processor 52. In a distributed environment, the software modules may be stored on a plurality of computer systems and executed by processors of the plurality of computer systems. Storage subsystem 56 typically comprises memory subsystem 58 and file storage subsystem 60.
Memory subsystem 58 typically includes a number of memories including a main random access memory (RAM) 70 for storage of instructions and data during program execution and a read only memory (ROM) 72 in which fixed instructions are stored. File storage subsystem 60 provides persistent (non-volatile) storage for program and data files, and may include tangible storage media 29 (
Bus subsystem 54 provides a mechanism for letting the various components and subsystems of computer system 22 communicate with each other as intended. The various subsystems and components of computer system 22 need not be at the same physical location but may be distributed at various locations within a distributed network. Although bus subsystem 54 is shown schematically as a single bus, alternate embodiments of the bus subsystem may utilize multiple busses.
Computer system 22 itself can be of varying types including a personal computer, a portable computer, a workstation, a computer terminal, a network computer, a control system in a wavefront measurement system or laser surgical system, a mainframe, or any other data processing system. Due to the ever-changing nature of computers and networks, the description of computer system 22 depicted in
Referring now to
More specifically, one wavefront measurement system 30 includes an image source 32, such as a laser, which projects a source image through optical tissues 34 of eye E so as to form an image 44 upon a surface of retina R. The image from retina R is transmitted by the optical system of the eye (e.g., optical tissues 34) and imaged onto a wavefront sensor 36 by system optics 37. The wavefront sensor 36 communicates signals to a computer system 22′ for measurement of the optical errors in the optical tissues 34 and/or determination of an optical tissue ablation treatment program. Computer 22′ may include the same or similar hardware as the computer system 22 illustrated in
Wavefront sensor 36 generally comprises a lenslet array 38 and an image sensor 40. As the image from retina R is transmitted through optical tissues 34 and imaged onto a surface of image sensor 40 and an image of the eye pupil P is similarly imaged onto a surface of lenslet array 38, the lenslet array separates the transmitted image into an array of beamlets 42, and (in combination with other optical components of the system) images the separated beamlets on the surface of sensor 40. Sensor 40 typically comprises a charged couple device or “CCD,” and senses the characteristics of these individual beamlets, which can be used to determine the characteristics of an associated region of optical tissues 34. In particular, where image 44 comprises a point or small spot of light, a location of the transmitted spot as imaged by a beamlet can directly indicate a local gradient of the associated region of optical tissue.
Eye E generally defines an anterior orientation ANT and a posterior orientation POS. Image source 32 generally projects an image in a posterior orientation through optical tissues 34 onto retina R as indicated in
In some embodiments, image source optics 46 may decrease lower order optical errors by compensating for spherical and/or cylindrical errors of optical tissues 34. Higher order optical errors of the optical tissues may also be compensated through the use of an adaptive optic element, such as a deformable mirror (described below). Use of an image source 32 selected to define a point or small spot at image 44 upon retina R may facilitate the analysis of the data provided by wavefront sensor 36. Distortion of image 44 may be limited by transmitting a source image through a central region 48 of optical tissues 34 which is smaller than a pupil 50, as the central portion of the pupil may be less prone to optical errors than the peripheral portion. Regardless of the particular image source structure, it will be generally be beneficial to have a well-defined and accurately formed image 44 on retina R.
In one embodiment, the wavefront data may be stored in a computer readable medium 29 or a memory of the wavefront sensor system 30 in two separate arrays containing the x and y wavefront gradient values obtained from image spot analysis of the Hartmann-Shack sensor images, plus the x and y pupil center offsets from the nominal center of the Hartmann-Shack lenslet array, as measured by the pupil camera 51 (
While the methods of the present invention will generally be described with reference to sensing of an image 44, a series of wavefront sensor data readings may be taken. For example, a time series of wavefront data readings may help to provide a more accurate overall determination of the ocular tissue aberrations. As the ocular tissues can vary in shape over a brief period of time, a plurality of temporally separated wavefront sensor measurements can avoid relying on a single snapshot of the optical characteristics as the basis for a refractive correcting procedure. Still further alternatives are also available, including taking wavefront sensor data of the eye with the eye in differing configurations, positions, and/or orientations. For example, a patient will often help maintain alignment of the eye with wavefront measurement system 30 by focusing on a fixation target, as described in U.S. Pat. No. 6,004,313, the full disclosure of which is incorporated herein by reference. By varying a position of the fixation target as described in that reference, optical characteristics of the eye may be determined while the eye accommodates or adapts to image a field of view at a varying distance and/or angles.
The location of the optical axis of the eye may be verified by reference to the data provided from a pupil camera 52. In the exemplary embodiment, a pupil camera 52 images pupil 50 so as to determine a position of the pupil for registration of the wavefront sensor data relative to the optical tissues.
An alternative embodiment of a wavefront measurement system is illustrated in
The components of an embodiment of a wavefront measurement system for measuring the eye and ablations may comprise elements of a WaveScan® system, available from AMO M
Relatedly, embodiments of the present invention encompass the implementation of any of a variety of optical instruments provided by WaveFront Sciences, Inc., including the COAS wavefront aberrometer, the ClearWave contact lens aberrometer, the CrystalWave IOL aberrometer, and the like. Embodiments of the present invention may also involve wavefront measurement schemes such as a Tscherning-based system, which may be provided by WaveFront Sciences, Inc. Embodiments of the present invention may also involve wavefront measurement schemes such as a ray tracing-based system, which may be provided by Tracey Technologies, Corp.
Ocular wavefront transformation is suitable for use in wavefront optics for vision correction because the pupil size of a human eye often changes due to accommodation or the change of lighting, and because the pupil constriction is commonly not concentric. Certain features of these ocular effects are discussed in, for example, Wilson, M. A. et al., Optom. Vis. Sci., 69:129-136 (1992), Yang, Y. et al., Invest. Ophthal. Vis. Sci., 43:2508-2512 (2002), and Donnenfeld, E. J., Refract. Surg., 20:593-596 (2004). For example, in laser vision correction, the pupil size of an eye is relatively large when an ocular wavefront is captured under an aberrometer. To obtain the entire ocular wavefront, it is often recommended that the ambient light be kept low so as to dilate the pupil size during the wavefront exam. A larger wavefront map can provide surgeons the flexibility for treatment over a smaller zone, because the wavefront information over any smaller zone within a larger zone is known. When a smaller wavefront map is captured, however, it is also useful to devise an accurate treatment over a larger zone. When the patient is under the laser, the pupil size can change due to changes in the ambient light. In many cases, the surgery room is brighter than a wavefront examination room, in particular when the patient is under the hood. Furthermore, the cyclorotation of the eye due to the change from a sitting position to a laying position can make the pupil center change between the wavefront capture and the laser ablation, for example as discussed in Chernyak, D. A., J. Cataract. Refract. Surg., 30:633-638 (2004). Theoretically, it has been reported that correction of error due to rotation and translation of the pupil can provide significant benefits in vision correction. Certain aspects of these ocular effects are discussed in Bard, S. et al., Appl. Opt., 39:3413-3420 (2000) and Guirao, A. et al., J. Opt. Soc. Am. A, 18:1003-1015 (2001).
Basis Data Techniques
Embodiments of the present invention encompass basis data architectures that are configured to efficiently operate with annular, elliptical, and slit laser beam shapes, and to account for position-dependent ablation features.
Beam Pulse Size and Shape
Variable Spot Scanning (VSS) or VSS Refractive™ technology refers to an excimer laser technique for scanning beams at variable pulse diameters at different locations (e.g. x,y position) over an entire treatment area. Variable Repetition Rate (VRR) refers to a pulse-packing technique, whereby the repetition rate of a laser can be varied, for example from 6 Hz to 20 Hz.
An exemplary illustration of the VSS technique is shown in
The mechanical block assembly 400b may operate with four free parameters, including iris diameter 440b, inner diameter 450b, X coordinate 460b, and Y coordinate 470b. With regard to the first parameter, the iris mechanism 410b can be adjusted to any dimension as desired, so as to provide the outer diameter of the annular shape. For example, iris mechanism 410b can be adjusted to a 6.5 mm outer diameter, a 6.0 mm outer diameter, a 5.5 mm outer diameter, and the like. With regard to the second parameter, the central block mechanism 420b can provide a 4.875 mm obscuration block, a 4.5 mm obscuration block, a 4.125 obscuration block, and the like, for the inner diameter dimension of the annular shape. In some cases where a circular ablation pulse or shape is desired, central block mechanisms can be adjusted, for example so that an obscuration blank is aligned with the iris 410b, so that a laser beam can pass through the iris without obscuration of a central portion of the laser beam. Related annular and other spot shape techniques are further described in US 2012/0083776, the content of which is incorporated herein by reference.
As depicted in
In contrast to a typical myopia treatment, a typical hyperopia treatment involves creating a donut-like ablation shape or treatment profile 500c, such as that shown in
For hyperopia treatments, it may be difficult to make extensive use of a large circular pulse (e.g. 6.5 mm in diameter). Accordingly, smaller circular pulse sizes can be used (e.g. maximum of 4.5 mm in diameter), although the efficiency of the ablation will likely be diminished. Similarly, for a mixed astigmatism treatment where one principal meridian is hyperopic and the other myopic, the efficiency is diminished when using smaller circular pulses to fit the target shape, due to the hyperopic meridian in the mixed astigmatic eye, and the ablation time is increased.
Embodiments of the present invention encompass annular, elliptical, and slit laser beam shape techniques for use with hyperopic and mixed astigmatism treatments. Exemplary aspects of such annular, elliptical, and slit pulse shapes are depicted in the side and top views provided in
For example,
Beam Pulse Position (Ablation Depth and Shape)
As depicted in
In some instances, the ablation depth of an off-center pulse (on a curved ablation surface) can be non-uniform, for example with the inner edge of the profile being deeper than the outer edge. For example, as shown in
As discussed elsewhere herein (e.g. with respect to
Similarly, as depicted in
Hence, as illustrated in
As depicted in
can be used to direct an incoming beam 905a toward various locations across the ablation surface 930a. In some instances, the scanning locations (e.g. locations 924a and 928a) can be characterized as occurring at a radial distance r relative to a central location (0, 0). In the embodiment shown here, the beams can be steered from a common point or element (e.g. corresponding to the steering lens 920a), which is a distance d from the ablation surface 930a. In some instances, distance d can be about 10 inches. As discussed elsewhere herein (e.g. with regard to
As depicted in
When the beam 910b is steered at an off-axis orientation, as depicted in the right panel, the symmetry of the beamlets within the beam is affected. For example, as shown here, some beamlets may become more perpendicular relative to the ablation surface, and other beamlets may be oriented at a lower incidence angle. Due to the combination of beamlets oriented at various angles non-uniform angles or steepness relative to the ablation surface 940b, the ablation spot 960b is non-symmetric. For example, the ablation spot may have a non-uniform or non-symmetric ablation depth, or a non-uniform or non-symmetric shape profile 962b. Put another way, the uniformity of the pulse shape deviates as the beam is delivered off-axis (e.g. relative to a flat ablation surface). This is because the ablation is created by multiple beamlets, which are symmetric when on-axis, but when steered in an off-axis orientation, the intersection of the beamlets at the ablation surface 940b no longer forms a symmetric pattern. This asymmetry as the beamlets impinge upon the ablation surface 940b can lead to hotter and colder positions in the beam profile. In some instances, the degree or extent of the asymmetry or non-uniformity can increase as the beam pulse is directed at further distances from the on-axis or central location 942b. For example, there may a significant asymmetry within the orientation of the beamlets at or near a transition zone (e.g. toward outer periphery) of an ablation pattern. A mask may be disposed between the beam focal plane 940b and the beam delivery optics.
Accordingly, in some instances, the ablation depth of an off-center pulse (on a flat ablation surface) can be non-uniform, for example with the inner edge 963b of the profile being deeper than the outer edge 964b. Hence, the ablation depth can vary according to the positioning of the beam pulse. In some instances, a greater amount of offset may correspond to a greater variability in the pulse depth profile. An ablation center can correspond to particular x,y scanning location (e.g. 0,0). At such a location, the system can be configured to direct the laser beam directly toward the surface of the eye (e.g. left panel of
Hence, as illustrated in
Basis Data Architecture
Embodiments of the present invention encompass basis data architectures that are configured to efficiently operate with annular, elliptical, and slit laser beam shapes, and to account for position-dependent ablation features.
In the treatment table architecture structure of
Relative to the treatment table, the basis data can be defined or stored in a separate file. According to some embodiments, certain features of the treatment table can be used to select information from a basis data file. For example, data associated with Column 4 (outer iris size 1008) of the treatment table can be used to determine which values can be selected from the basis data file. The information obtained from the basis data file can be read into a memory, for example during start up of the treatment software. According to some embodiments, the basis data is read in with respect to a treatment table feature (e.g. circular iris size), and mask and/or apodization techniques can be applied to the basis data, for example during the assembly of the entire ablation profile.
Column 4 is for the outer iris size 1008 (diameter in mm). For the general circular pulse (e.g. iris type 0), this will be the spot size. For the elliptical iris type (e.g. iris type 1), this will be the (major) long axis length of the ellipse. For the annular iris (e.g. iris type 2), this will be the outer iris size. For the slit iris type (e.g. iris type 3), this will be the length of the slit.
Column 5 is for the inner iris size or the slit width 1010. For the general circular iris type (e.g. iris type 0), this will be zero. For the elliptical iris type (e.g. iris type 1), this will be the minor (short) axis length of the ellipse. For the annular iris type (e.g. iris type 2), this will be the inner iris size. That is, the laser beam will pass the energy between the two circles having the outer boundary of the outer iris size and the inner boundary of the inner iris size. For the slit iris type (e.g. iris type 3), this will be the width of the slit.
Hence, it can be seen that certain Column combinations can inference a particular mask or iris configuration. For example, the annular mask can correspond to the outer iris size or diameter of Column 4 and the inner iris size or diameter of Column 5. Similarly, the elliptical mask can correspond to the major axis length of Column 4 and the minor axis length of Column 5. Further, the slit mask can correspond to the slit length of Column 4 and the slit width of Column 5. Accordingly, Columns 2, 4, and 5 can be used to determine characteristics of a mask.
Column 6 is for the slit offset 1012. For both the circular and the annular iris types (e.g. iris types 0 and 2), this will be zero. For the elliptical and the slit iris types (e.g. iris types 1 and 3), this will be the offset of the pulse. According to some embodiments, the elliptical and/or slit pulse shapes can be used to ablate the hyperopia shape.
Column 7 is for the slit angle 1014, which is used for the elliptical and slit iris types (e.g. types 1 and 3). Columns 8 and 9 are for the x- and y-scanning locations, 1016 and 1018, respectively. They can be used for all iris types (e.g. iris types 0, 1, 2, and 3). In a Variable Spot Scanning system, individual pulses can be directed to associated x,y locations. In some cases, Columns 8 and 9 may be used primarily for the circular and annular pulses (e.g. iris types 0 and 2). Column 10 is for the laser repetition rate or inter-pulse delay 1020, and can correspond to the delay that is used between consecutive pulses, which may be measured in mini-seconds. Column 11 is for indicating whether the treatment is wavefront guided 1022.
As shown here, aspects of Columns 2, 4, 5, 8, and/or 9 can be used to determine a crater or pulse shape 1030, which is then used to determine an ablation or target shape 1040 of a treatment. For example, an apodization or adjustment function 1050 can be applied to a pulse basis data profile 1070, to determine the crater or pulse shape 1030. As discussed elsewhere herein, the basis data 1070 can include or correspond to a basis data energy (or fluence) profile, and the pulse shape 1030 can include or correspond to a pulse ablation profile. The adjustment can be performed on individual pulse spots of the treatment, and in some cases can be specific to the particular pulse spot. In some cases, the adjustment function can account for position dependent asymmetry associated with the basis data. For example, an adjustment function may include a weighting function, such that the basis data is modified based on a radial distance from the treatment center, or that is based on a x,y scanning position. Exemplary position dependent asymmetry features are discussed elsewhere herein, relative to
According to some embodiments, pulse shapes such as shape 1032a, rather than pulse basis data profiles such as profile 1012a, can be used to generate a target ablation shape. For example, as shown in the lower panel of
Any of a variety of factors associated with the laser or optical path of a beam may contribute to apodization of a pulse shape. For example, a lens, an aperture edge, a laser cavity, a laser beam energy, an off-axis beam orientation, or the like, can have an impact on the pulse shape. In some cases, an apodization function can be associated with a single factor, or with a combination of factors. For example, an apodization function can be associated with a lens at the exit pupil of a laser device. Relatedly, an apodization function can be associated with an aperture edge taken in combination with a lens. In some cases, an apodization function can be determined using an empirical approach. In some cases, an apodization function can be determined using a theoretical approach.
As depicted in
In some cases, the apodization or adjustment function can be calculated on the fly, for example to account for situations which may occur during the ablation procedure. For example, where a closed-loop system is used to monitor the ablation progression, and under-ablation or over-ablation is realized, an apodization function may be applied to adjust each of the subsequent basis data to compensate for the deviation. According to some embodiments, the deviation can be represented by or related to the difference between the intended ablation depth or profile (or shape) and the measured ablation depth or profile (or shape). According to some embodiments, the deviation can be represented by or related to the difference between the intended ablation depth or profile (or shape) and the measured ablation depth or profile (or shape) of the summation of pulses laid down up until that time. In some cases, the apodization function can be determined based on the under-ablation, over-ablation, or other deviation. As another example, if a similar monitoring system detects a deviation of the basis data itself, which may be affected by certain environmental factors (e.g. temperature, humidity, and the like), particularly associated with transition of the edge of the mask, a different apodization function may be used. In some instances, it may be desirable to not apply a weighting function to basis data. In some instances, a weighting function can be set to “1” or some other number or value, such that no adjustment or apodization is applied to the basis data. In some instances, it may be desirable to only apply an adjustment where the beam is decentered, and to not apply an adjustment where the beam is centered. In some instances, a decision whether to apply an adjustment can be based on the iris shape. In some instances, a weighting function can depend on the iris shape. In some cases, a weighting function can be provided as a two dimensional matrix.
In some cases, a particular iris type configuration can be achieved using an optical transformation technique, instead of using a mask. For example, an elliptical iris type can be achieved using an optical transform mechanism, such as a tilted cone type object. Such optical transform hardware elements can be used to impart various shapes to the ablation pulse beam.
As depicted in
Embodiments of the present invention encompass techniques which account for smoothing or transition effects associated with basis data for particular pulse shape. Similarly, embodiments encompass techniques which account for effects related to decentering or x,y scanning locations 1112 of the pulse beam. To account for such effects, a new basis data architecture is proposed. In some instances, this architecture may be used with existing basis data files without modifying them. As depicted here, the basis data assembly process may include steps such as introducing a mask 1110 to account for different iris shapes, and using an apodization function 1114 to account for position-dependent ablation features. Individual pulses 1116 can be added to previous pulses 1118, so as to provide the ablated profile 1120.
In general terms, basis data can correspond to or be defined by the volumetric profile of material removed for a single laser pulse. There may be different sets of basis data corresponding to different types of material. For example, basis data can correspond to human corneal tissue material. Such basis data can be generated based on ablation studies using human eyes, including clinical trials and the like. As discussed elsewhere herein, a pulse ablation profile can be determined based on a basis data energy (or fluence) profile and an apodization function. In some cases, a measured pulse ablation profile obtained from a treated tissue reflects the effects of apodization. In this sense, the measured pulse ablation profile data can be considered to account for or incorporate certain apodization effects, such as off-axis orientation, lens effects, aperture edge effects, and the like.
As depicted in
In the basis data profiles shown in
With regard to the smoothing or transition effects depicted in
For example, a least square fitting approach can be used to analyze the data. In some cases, it is possible to obtain a target and a simulated target, and compare the two targets with a minimum root mean square error approach, to evaluate a good fit. In some cases, simulated annealing techniques such as those described in PCT Application No. PCT/US01/08337 (incorporated herein by reference) can be used.
Results such as those obtained in
As with the representations shown in
It can be seen in
Embodiments of the present invention further encompass techniques that involve the application of a first pulse regimen (e.g. using a first mask shape) in combination with a second pulse regimen (e.g. using a second mask shape) so as to produce an ablation shape. In this way, it is possible to achieve a result such as that depicted in
According to preliminary studies, by using various iris types, it may be possible to provide hyperopic ablation treatments that can be performed more quickly, while at the same time keeping the ablation smooth. In some instances, the smoothness can be evaluated based on a root mean square analysis (e.g. low RMS), or on a peak to valley analysis (e.g. low PV error). For example, annular, elliptical, or slit shapes can be used to decrease the amount of time involved for performing a hyperopia treatment.
As illustrated by
The treatment table and basis data embodiments disclosed herein are well suited for use in a variety of vision correction modalities, including the STAR S4 IRTM Excimer Laser System with VSS Refractive™ technology (Variable Spot Scanning) In some cases, embodiments may encompass the use of existing single-spot energy profiles, or basis data, which are adjusted based on factors such as iris type and/or x,y scanning location. For example, shape-related masks can be used to redefine the boundary of the revised energy profile. Similarly, apodization functions can be used to reflect the smooth transition of the boundaries to account for practical implementation. When using the root mean squares (RMS) error, peak-to-valley (PV) error, and the ablation time as comparison metrics, it has been observed that an elliptical iris type can provide a highly accurate and efficient ablation shape for hyperopic and mixed astigmatic ablations. Use of noncircular ablation pulses can speed up a hyperopic treatment without a loss of fitting accuracy of the target shape.
Determination of Treatment Shape
In some embodiments, systems and methods may involve producing a treatment shape in a variety of steps. For example, an optical region shape can be determined, either by Munnerlyn equations or wavefront techniques. In some cases, aspects of the shape can be smoothed by pixel averaging, or by spatial averaging of depth.
Once the desired ablation shape has been determined, a next step is to define the parameters of the actual laser ablation required to administer the treatment ablation profile. A particularly useful way of determining these parameters is by using an ablation equation, such as the one shown below.
In brief, this equation is based on the principle that a treatment ablation is the sum of each of the individual laser pulses. This equation has been empirically verified on a variety of materials including plastic, and bovine, porcine, and human corneal tissue.
In this equation, the AblationShape variable represents the desired ablation shape. In this sense, it is a known variable. The target shape can be, for example, a simple sphere, an ellipse, a cylinder for treating myopia or hyperopia, or even a saddle for treating mixed astigmatism. The target shape can be any arbitrary shape, such as the map from a wavefront type device or any other topography system.
The PulseShape variable, which is also a known variable, represents the ablation shape of each laser pulse size to be used. The PulseShape typically varies for different ablated materials, such as plastic, animal cornea, or human cornea. The PulseShape also typically varies for each laser pulse diameter. Certain PulseShape features are described herein at
A fixed spot laser may have only one description, while a variable spot laser could have as many as desired. There is no requirement that the crater shape be flat, round, or symmetric. As long as it can be described mathematically or with an array of data, it can be incorporated in the equation.
In order to create the ablated surface, it is useful to determine the locations where each of the laser pulses will be applied. The Position variable, which represents the exact position of every laser pulse, is an unknown variable. Certain Position features are described herein at
The target ablation shape is a theoretical construct; it is a mathematically perfect representation of a desired ablation outcome. Put another way, while the application of thousands of specifically placed brief laser pulses can create an actual ablation shape that approaches the ideal target ablation shape, in the end it is still an approximation thereof.
Therefore, solving for the Position variable can allow for the formulation of a corresponding ablation shape that approaches the target ablation shape as closely as possible. In this way each of the thousands of pulse positions are individually determined so as to minimize the difference between the ideal target ablation shape and the actual resulting ablation shape. In a system for ablating tissue using a scanning laser, a presently preferred computational technique for achieving this goal employs simulated annealing.
Other mathematical approaches include, for example, the SALSA Algorithm. SALSA is an acronym for Simulated Annealing Least Squares Algorithm. It is an algorithm that solves an equation having over 10,000 unknowns. The algorithm finds the best solution by selecting: the number of pulses, the size of each pulse, and the location of each pulse. It is an exact algorithm, and makes no statistical assumptions.
Simulated Annealing is a recent, proven method to solve otherwise intractable problems, and may be used to solve the ablation equation discussed above. This is more fully described in PCT Application No. PCT/US01/08337, filed Mar. 14, 2001, the entire disclose of which is incorporated herein by reference. See also W. H. Press et al., “Numerical Recipes in C” 2nd Ed., Cambridge University Press, pp. 444-455 (1992). This approach is also further discussed in co-pending U.S. patent application Ser. No. 09/805,737, the entire disclosure of which is incorporated herein by reference.
Simulated annealing is a method used for minimizing (or maximizing) the parameters of a function. It is particularly suited to problems with very large, poorly behaved function spaces. Simulated annealing can be applied in the same way regardless of how many dimensions are present in the search space. It can be used to optimize any conditions that can be expressed numerically, and it does not require a derivative. It can also provide an accurate overall minimum despite local minima in the search space, for example.
As discussed elsewhere herein, for certain broad-beam lasers, the ablation time for hyperopia may be much longer than myopia due to the use of relatively smaller spots. In some cases, lengthy ablation procedures may result in corneal dehydration, and consequently, the clinical outcome may become sub-optimal. It has been observed that the US population consists of 35% hyperopic people, and 15% are hyperopic among laser treatment patients. It has been discovered that certain non-circular ablation pulse shapes (e.g. annular, elliptical, and slit) can be used to speed up laser treatment time for hyperopia.
The methods and apparatuses of the present invention may be provided in one or more kits for such use. The kits may comprise a system for profiling an optical surface, such as an optical surface of an eye, and instructions for use. Optionally, such kits may further include any of the other system components described in relation to the present invention and any other materials or items relevant to the present invention. The instructions for use can set forth any of the methods as described above.
Each of the calculations or operations described herein may be performed using a computer or other processor having hardware, software, and/or firmware. The various method steps may be performed by modules, and the modules may comprise any of a wide variety of digital and/or analog data processing hardware and/or software arranged to perform the method steps described herein. The modules optionally comprising data processing hardware adapted to perform one or more of these steps by having appropriate machine programming code associated therewith, the modules for two or more steps (or portions of two or more steps) being integrated into a single processor board or separated into different processor boards in any of a wide variety of integrated and/or distributed processing architectures. These methods and systems will often employ a tangible media embodying machine-readable code with instructions for performing the method steps described above. Suitable tangible media may comprise a memory (including a volatile memory and/or a non-volatile memory), a storage media (such as a magnetic recording on a floppy disk, a hard disk, a tape, or the like; on an optical memory such as a CD, a CD-R/W, a CD-ROM, a DVD, or the like; or any other digital or analog storage media), or the like.
All patents, patent publications, patent applications, journal articles, books, technical references, and the like discussed in the instant disclosure are incorporated herein by reference in their entirety for all purposes.
While the above provides a full and complete disclosure of the preferred embodiments of the present invention, various modifications, alternate constructions and equivalents may be employed as desired. Therefore, the above description and illustrations should not be construed as limiting the invention, which can be defined by the appended claims.
This application claims the benefit of U.S. Provisional Application No. 61/724,111 filed Nov. 8, 2012 and U.S. Provisional Application No. 61/765,567 filed Feb. 15, 2013. This application is also related to U.S. patent application Ser. No. 12/897,946 filed Oct. 5, 2010. The content of each of the above filings is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61724111 | Nov 2012 | US | |
| 61765567 | Feb 2013 | US |
