Patent Description:
Vision impairments such as myopia (near-sightedness), hyperopia and astigmatism can be corrected using eyeglasses or contact lenses. Alternatively, the cornea of the eye can be reshaped surgically to provide the needed optical correction. Eye surgery has become commonplace with some patients pursuing it as an elective procedure to avoid using contact lenses or glasses to correct refractive problems, and others pursuing it to correct adverse conditions such as cataracts. And, with recent developments in laser technology, laser surgery is becoming the technique of choice for ophthalmic procedures. The reason eye surgeons prefer a surgical laser beam over manual tools like microkeratomes and forceps is that the laser beam can be focused precisely on extremely small amounts of ocular tissue, thereby enhancing accuracy and reliability of the procedure. These in turn enable better wound healing and recovery following surgery.

Hyperopia (far-sightedness) is a visual impairment where light entering the eye does not focus at the retina to produce a sharp image as desired, but rather focuses at a location behind the retina such that a patient sees a blurred disc. The basic principle to treating hyperopia is to add positive focusing power to the cornea. For instance, a hyperopic eye can be treated by placing a convex lens in front of the eye to add a positive focusing power to the eye. After correction, light passing through the convex lens and into the eye focuses at the retina to form a sharp image.

Different laser eye surgical systems use different types of laser beams for the various procedures and indications. These include, for instance, ultraviolet lasers, infrared lasers, and near-infrared, ultra-short pulsed lasers. Ultra-short pulsed lasers emit radiation with pulse durations as short as <NUM> femtoseconds and as long as <NUM> nanoseconds, and a wavelength between <NUM> and <NUM>. Examples of laser systems that provide ultra-short pulsed laser beams include the Abbott Medical Optics iFS Advanced Femtosecond Laser, the IntraLase FS Laser, and the OptiMedica Catalys Precision Laser System.

Prior surgical approaches for reshaping the cornea include laser assisted in situ keratomileusis (hereinafter "LASIK"), photorefractive keratectomy (hereinafter "PRK") and Small Incision Lens Extraction (hereinafter "SMILE").

In the LASIK procedure, an ultra-short pulsed laser is used to cut a corneal flap to expose the corneal stroma for photoablation with ultraviolet beams from an excimer laser. Photoablation of the corneal stroma reshapes the cornea and corrects the refractive condition such as myopia, hyperopia, astigmatism, and the like.

It is known that if a part of the cornea is removed, the pressure exerted on the cornea by the aqueous humor in the anterior chamber of the eye will act to close the void created in the cornea, resulting in a reshaped cornea. By properly selecting the size, shape and location of a corneal void, one can obtain the desired shape, and hence, the desired optical properties of the cornea.

In traditional laser surgery treatments, such as LASIK and PRK that correct hyperopia, positive focusing power is added to the cornea by steepening the curvature of the cornea, by for example, removing a ring-shaped stroma material from the cornea. As described earlier, in a LASIK procedure, a flap is first created, and then lifted so the ring-shaped stroma material can be removed or ablated away by an excimer laser. The center of the cornea is not removed while more outward portions of the cornea are removed. The flap is then put back into place. The cornea thus steepens due to the void created in the cornea. Common patterns that steepen the cornea include ring, tunnel, and toric shapes. LASIK can typically correct hyperopia for up to 5D (diopter). In a PRK procedure, no flap is created in the cornea. Instead, an excimer laser is used to first remove the epithelium layer, and then, the ring-shaped stroma material. Typically, the epithelium layer grows back a few days after the PRK procedure.

More recently, surgeons have started using another surgical technique called small incision lenticule extraction (SMILE) for refractive correction. The SMILE procedure is different from LASIK and PRK. Instead of ablating corneal tissue with an excimer laser, the SMILE technique involves tissue removal with two femtosecond laser incisions that intersect to create a lenticule, which is then extracted. Lenticular extractions can be performed either with or without the creation of a corneal flap. With the flapless procedure, a refractive lenticule is created in the intact portion of the anterior cornea and removed through a small incision.

In the SMILE procedure illustrated in <FIG>, a femtosecond laser <NUM> is used tomake a side cut <NUM>, an upper surface cut <NUM>, and a lower surface cut <NUM> that forms a cut lens <NUM>. An instrument like a tweezer, for example, is then used to extract the cut lens beneath the anterior surface of the cornea <NUM> through the side cut <NUM>.

While, SMILE has been applied to treat myopia by cutting and extracting a convex lens-shaped stroma material with a femtosecond laser, the technique has not been applied in treating hyperopia.

Prior art systems and procedures are disclosed in documents <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Further, as shown in <FIG>, conventional femtosecond laser surgery systems generate a curved dissection surface to make a lenticular incision by scanning a laser focus on the intended dissection surface through a XY-scanning device and a Z-scanning device. This method does not use the more advantageous "fast-scan-slow-sweep" scanning scheme with femtosecond lasers having high repetition rate ("rep rate"), for e.g., in the MHz range. Using the "fast-scan-slow-sweep" scanning scheme for a lenticular incision, however, will generate vertical "steps" and will require many vertical side cuts, resulting in a lenticular dissection surface that is not smooth.

Therefore, there is a need for improved systems to generate corneal lenticular incisions for high repetition rate femtosecond lasers to correct hyperopia.

Hence, to obviate one or more problems due to limitations and disadvantages of the related art, this invention provides an ophthalmic surgical laser system comprising a laser capable of generating a pulsed laser beam and a delivery system for delivering the pulsed laser beam to a target in a subject's eye, an XY-scan device to deflect the pulsed laser beam, a Z-scan device to modify a depth of a focus of the pulsed laser beam, and a controller configured to form a top lenticular incision and a bottom lenticular incision of a lens on the subject's eye. The focal spots have a diameter between <NUM> and <NUM> and the spaced focal spots in the pattern overlap. The XY-scan device deflects the pulsed laser beam to form a scan line. The scan line is tangential to the parallels of latitude of the lens. The scan line is then moved along the meridians of longitude of the lens. The top lenticular incision is moved over the top surface of the lens through the apex of the top surface of the lens, and the bottom lenticular incision is moved over the bottom surface of the lens through the apex of bottom surface of the lens.

The system here can be used to direct an ophthalmic surgical femtosecond laser beam into an intrastromal corneal layer of a patient, pre-compensate dispersion of the laser beam path, focus the laser beam into a focal spot to disrupt cells in the intrastromal corneal layer, move the laser beam to create a pattern of overlapping focal spots inside the intrastromal corneal layer, incise a lens with the overlapping focal spots in the intrastromal corneal layer of the patient, wherein the focal spots have a diameter between <NUM>,<NUM> and <NUM>,<NUM>. Alternatively or additionally, a wavelength of the laser is between <NUM> and <NUM>. Alternatively or additionally, a wavelength of the laser is between <NUM> and <NUM>. Alternatively or additionally, the spot spacing is between <NUM> and <NUM> from center to center of the spots. Alternatively or additionally, the spot spacing is less than <NUM> from center to center of the spots. The spots in the pattern overlap. Alternatively or additionally, a frequency of the laser is between <NUM> and <NUM>. Alternatively or additionally, a frequency of the laser is <NUM>. Alternatively or additionally, a pulse width of the laser is between <NUM> fs and <NUM> fs. Alternatively or additionally, a pulse width of the laser is between <NUM> fs and <NUM> fs. Alternatively or additionally, an energy for one spot is between <NUM> nJ and <NUM> nJ. Alternatively or additionally, an energy for one spot is between <NUM> nJ and <NUM> nJ. In some embodiments, scanning the laser beam to produce a scan line, wherein the scanning is between <NUM>,<NUM> to <NUM>,<NUM>.

This summary and the following detailed description are merely exemplary, illustrative, and explanatory, and are not intended to limit, but to provide further explanation of the invention as claimed. Additional features and advantages of the embodiments will be set forth in the descriptions that follow, and in part will be apparent from the description, or may be learned by practice of the embodiments. The objectives and other advantages of the embodiments will be realized and attained by the structure particularly pointed out in the written description, claims and the appended drawings.

The novel features of the embodiments are set forth with particularity in the appended claims. A better understanding of the features and advantages will be facilitated by referring to the following detailed description that sets forth illustrative embodiments using principles of the embodiments, as well as to the accompanying drawings, in which like numerals refer to like parts throughout the different views. Like parts, however, do not always have like reference numerals. Further, the drawings are not drawn to scale, and emphasis has instead been placed on illustrating the principles of the embodiments. All illustrations are intended to convey concepts, where relative sizes, shapes, and other detailed attributes may be illustrated schematically rather than depicted literally or precisely.

Referring to the drawings, <FIG> shows a system <NUM> for making an incision in a material <NUM>. The system <NUM> includes, but is not limited to, a laser <NUM> capable of generating a pulsed laser beam <NUM>, an energy control module <NUM> for varying the pulse energy of the pulsed laser beam <NUM>, a Z-scanner <NUM> for modifying the depth of the pulse laser beam <NUM>, a controller <NUM>, a prism <NUM> (e.g., a Dove or Pechan prism, or the like), and an XY-scanner <NUM> for deflecting or directing the pulsed laser beam <NUM> from the laser <NUM> on or within the material <NUM>. The controller <NUM>, such as a processor operating suitable control software, is operatively coupled with the Z-scanner <NUM>, the XY-scanner <NUM>, and the energy control unit <NUM> to direct a scan line <NUM> of the pulsed laser beam along a scan pattern on or in the material <NUM>. In this embodiment, the system <NUM> further includes a beam splitter <NUM> and a detector <NUM> coupled to the controller <NUM> for a feedback control mechanism (not shown) of the pulsed laser beam <NUM>. Other feedback methods may also be used, including but not necessarily limited to position encoder on the scanner <NUM>, or the like. In an embodiment, the pattern of pulses may be summarized in machine readable data of tangible storage media in the form of a treatment table. The treatment table may be adjusted according to feedback input into the controller <NUM> from an automated image analysis system in response to feedback data provided from an ablation monitoring system feedback system (not shown). Optionally, the feedback may be manually entered into the controller <NUM> by a system operator. The feedback may also be provided by integrating a wavefront measurement system (not shown) with the laser surgery system <NUM>. The controller <NUM> may continue and/or terminate a sculpting or incision in response to the feedback, and may also modify the planned sculpting or incision based at least in part on the feedback. Measurement and imaging systems are further described in U. <NUM>,<NUM>,<NUM> and <NUM>,<NUM>,<NUM>.

In an embodiment, the system <NUM> uses a pair of scanning mirrors or other optics (not shown) to angularly deflect and scan the pulsed laser beam <NUM>. For example, scanning mirrors driven by galvanometers may be employed where each of the mirrors scans the pulsed laser beam <NUM> along one of two orthogonal axes. A focusing objective (not shown), whether one lens or several lenses, images the pulsed laser beam <NUM> onto a focal plane of the system <NUM>. The focal point of the pulsed laser beam <NUM> may thus be scanned in two dimensions (e.g., the x-axis and the y-axis) within the focal plane of the system <NUM>. Scanning along the third dimension, i.e., moving the focal plane along an optical axis (e.g., the z-axis), may be achieved by moving the focusing objective, or one or more lenses within the focusing objective, along the optical axis.

Laser <NUM> may comprise a femtosecond laser capable of providing pulsed laser beams, which may be used in optical procedures, such as localized photodisruption (e.g., laser induced optical breakdown). Localized photodisruptions can be placed at or below the surface of the material to produce high-precision material processing. For example, a micro-optics scanning system may be used to scan the pulsed laser beam to produce an incision in the material, create a flap of the material, create a pocket within the material, form removable structures of the material, and the like. The term "scan" or "scanning" refers to the movement of the focal point of the pulsed laser beam along a desired path or in a desired pattern.

In other embodiments, the laser <NUM> may comprise a laser source configured to deliver an ultraviolet laser beam comprising a plurality of ultraviolet laser pulses capable of photodecomposing one or more intraocular targets within the eye.

Although the laser system <NUM> may be used to photoalter a variety of materials (e.g., organic, inorganic, or a combination thereof), the laser system <NUM> is suitable for ophthalmic applications in some embodiments. In these cases, the focusing optics direct the pulsed laser beam <NUM> toward an eye (for example, onto or into a cornea) for plasma mediated (for example, non-UV) photoablation of superficial tissue, or into the stroma of the cornea for intrastromal photodisruption of tissue. In these embodiments, the surgical laser system <NUM> may also include a lens to change the shape (for example, flatten or curve) of the cornea prior to scanning the pulsed laser beam <NUM> toward the eye.

The laser system <NUM> is capable of generating the pulsed laser beam <NUM> with physical characteristics similar to those of the laser beams generated by a laser system disclosed in <CIT>, <CIT>, and <CIT>.

<FIG> shows another exemplary diagram of the laser system <NUM>. <FIG> shows a moveable XY-scanner (or XY-stage) <NUM> of a miniaturized femtosecond laser system. In this embodiment, the system <NUM> uses a femtosecond oscillator, or a fiber oscillator-based low energy laser. This allows the laser to be made much smaller. The laser-tissue interaction is in the low-density-plasma mode. An exemplary set of laser parameters for such lasers include pulse energy in the <NUM>-100nJ range and pulse repetitive rates (or "rep rates") in the <NUM>-<NUM> range. A fast-Z scanner <NUM> and a resonant scanner <NUM> direct the laser beam <NUM> to the prism <NUM>. When used in an ophthalmic procedure, the system <NUM> also includes a patient interface <NUM> design that has a fixed cone nose and a portion that engages with the patient's eye. A beam splitter is placed inside the cone of the patient interface to allow the whole eye to be imaged via visualization optics. In one embodiment, the system <NUM> uses: optics with a <NUM> numerical aperture (NA) which would produce <NUM> Full Width at Half Maximum (FWHM) focus spot size; and a resonant scanner <NUM> that produces <NUM>-<NUM> scan line with the XY-scanner scanning the resonant scan line to a <NUM> field. The prism <NUM> rotates the resonant scan line in any direction on the XY plane. The fast-Z scanner <NUM> sets the incision depth and produces a side cut. The system <NUM> may also include an auto-Z module <NUM> to provide depth reference. The miniaturized femtosecond laser system <NUM> may be a desktop system so that the patient sits upright while being under treatment. This eliminates the need of certain opto-mechanical arm mechanism(s), and greatly reduces the complexity, size, and weight of the laser system. Alternatively, the miniaturized laser system may be designed as a conventional femtosecond laser system, where the patient is treated while lying down.

<FIG> illustrates a simplified block diagram of an exemplary controller <NUM> that may be used by the laser system <NUM>. Controller <NUM> typically includes at least one processor <NUM> which may communicate with a number of peripheral devices via a bus subsystem <NUM>. These peripheral devices may include a storage subsystem <NUM>, comprising a memory subsystem <NUM> and a file storage subsystem <NUM>, user interface input devices <NUM>, user interface output devices <NUM>, and a network interface subsystem <NUM>. Network interface subsystem <NUM> provides an interface to outside networks <NUM> and/or other devices. Network interface subsystem <NUM> includes one or more interfaces known in the arts, such as LAN, WLAN, Bluetooth, other wire and wireless interfaces, and so on.

User interface input devices <NUM> may include a keyboard, pointing devices such as a mouse, trackball, touch pad, or graphics tablet, a scanner, foot pedals, a joystick, a touch screen incorporated into a display, audio input devices such as voice recognition systems, microphones, and other types of input devices. In general, the term "input device" is intended to include a variety of conventional and proprietary devices and ways to input information into controller <NUM>.

The display subsystem may be a flat-panel device such as a liquid crystal display (LCD), a light emitting diode (LED) display, a touchscreen display, or the like. The display subsystem may also provide a non-visual display such as via audio output devices. In general, the term "output device" is intended to include a variety of conventional and proprietary devices and ways to output information from controller <NUM> to a user.

Storage subsystem <NUM> can store the basic programming and data constructs that provide the functionality of the various embodiments. For example, a database and modules implementing the functionality of the present embodiments, as described herein, may be stored in storage subsystem <NUM>. These software modules are generally executed by processor <NUM>. 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 <NUM> typically comprises memory subsystem <NUM> and file storage subsystem <NUM>.

Memory subsystem <NUM> typically includes a number of memories including a main random access memory (RAM) <NUM> for storage of instructions and data during program execution and a read only memory (ROM) <NUM> in which fixed instructions are stored. File storage subsystem <NUM> provides persistent (non-volatile) storage for program and data files. File storage subsystem <NUM> may include a hard disk drive along with associated removable media, a Compact Disk (CD) drive, an optical drive, DVD, solid-state memory, and/or other removable media. One or more of the drives may be located at remote locations on other connected computers at other sites coupled to controller <NUM>. The modules implementing the functionality of some embodiments may be stored by file storage subsystem <NUM>.

Bus subsystem <NUM> provides a mechanism for letting the various components and subsystems of controller <NUM> communicate with each other as intended. The various subsystems and components of controller <NUM> need not be at the same physical location but may be distributed at various locations within a distributed network. Although bus subsystem <NUM> is shown schematically as a single bus, alternate embodiments of the bus subsystem may utilize multiple busses.

Due to the ever-changing nature of computers and networks, the description of controller <NUM> depicted in <FIG> is intended only as an example for purposes of illustrating only one embodiment. Many other configurations of controller <NUM>, having more or fewer components than those depicted in <FIG>, are possible.

As should be understood by those of skill in the art, additional components and subsystems may be included with laser system <NUM>. For example, spatial and/or temporal integrators may be included to control the distribution of energy within the laser beam, as described in <CIT>. Ablation effluent evacuators/filters, aspirators, and other ancillary components of the surgical laser system are known in the art, and may be included in the system. In addition, an imaging device or system may be used to guide the laser beam. Further details of suitable components of subsystems that can be incorporated into an ophthalmic laser system for performing the procedures described here can be found in commonly-assigned <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

In an embodiment, the laser surgery system <NUM> includes a femtosecond oscillator-based laser operating in the MHz range, for example, <NUM>, for example, from several MHz to tens of MHz. For ophthalmic applications, the XY-scanner <NUM> may utilize a pair of scanning mirrors or other optics (not shown) to angularly deflect and scan the pulsed laser beam <NUM>. For example, scanning mirrors driven by galvanometers may be employed, each scanning the pulsed laser beam <NUM> along one of two orthogonal axes. A focusing objective (not shown), whether one lens or several lenses, images the pulsed laser beam onto a focal plane of the laser surgery system <NUM>. The focal point of the pulsed laser beam <NUM> may thus be scanned in two dimensions (e.g., the X-axis and the Y-axis) within the focal plane of the laser surgery system <NUM>. Scanning along a third dimension, i.e., moving the focal plane along an optical axis (e.g., the Z-axis), may be achieved by moving the focusing objective, or one or more lenses within the focusing objective, along the optical axis. It is noted that in many embodiments, the XY-scanner <NUM> deflects the pulse laser beam <NUM> to form a scan line.

In other embodiments, the beam scanning can be realized with a "fast-scan-slow-sweep" scanning scheme. The scheme consists of two scanning mechanisms: first, a high frequency fast scanner is used to produce a short, fast scan line (e.g., a resonant scanner <NUM> of <FIG>); second, the fast scan line is slowly swept by much slower X, Y, and Z scan mechanisms. <FIG> illustrates a scanning example of a laser system <NUM> using an <NUM> resonant scanner <NUM> to produce a scan line of about l mm and a scan speed of about <NUM>/sec, and X, Y, and Z scan mechanisms with the scan speed smaller than <NUM>/sec. The fast scan line may be perpendicular to the optical beam propagation direction, i.e., it is always parallel to the XY plane. The trajectory of the slow sweep can be any three dimensional curve drawn by the X, Y, and Z scanning devices (e.g., XY-scanner <NUM> and Z-scanner <NUM>). An advantage of the "fast-scan-slow-sweep" scanning scheme is that it only uses small field optics (e.g., a field diameter of <NUM>) which can achieve high focus quality at relatively low cost. The large surgical field (e.g., a field diameter of <NUM> or greater) is achieved with the XY-scanner, which may be unlimited.

In another embodiment shown in <FIG>, the laser system <NUM> creates a smooth lenticular cut using the "fast-scan-slow-sweep" scanning scheme under a preferred procedure. First, in a three dimensional lenticular cut, the fast scan line is preferably placed tangential to the parallels of latitude <NUM>. For example, in the miniaturized flap maker laser system <NUM> of <FIG>, this can be realized by adjusting a prism <NUM> to the corresponding orientations via software, e.g., via the controller <NUM>. Second, the slow sweep trajectory preferably moves along the meridians of longitude <NUM>. For example, in the miniaturized flap maker system of <FIG>, this can be done by coordinating the XY scanner <NUM>, and the Fast-Z scanner <NUM> via the software, e.g., via the controller <NUM>. The procedure starts with the scan line being parallel to the XY plane, and sweeps through the apex of the lens, following the curvature with the largest diameter (see also <FIG>). With this preferred procedure, there are no vertical "steps" in the dissection, and vertical side cuts are eliminated. As will be analyzed herein below, the deviations between the laser focus locations and the intended spherical surface dissections are also minimized.

<FIG> shows the geometric relation between the fast scan line <NUM> and the intended spherical dissection surface <NUM>, e.g., of a lens, especially the distance deviation (δ) between the end point B of the scan line <NUM> and point A on the intended dissection surface <NUM>. The maximum deviation δ is the distance between point A and point B, and is given by
<MAT>where R is greater than L. R is the radius of curvature of the surface dissection <NUM>, and L is the length of the fast scan.

In an exemplary case of myopic correction, the radius of curvature of the surface dissection may be determined by the amount of correction, ΔD, using the following equation
<MAT> where n = <NUM>, which is the refractive index of cornea, and R<NUM> and R<NUM> (may also be referred herein as Rt and Rb) are the radii of curvature for the top surface and bottom surface of a lenticular incision, respectively. For a lenticular incision with R<NUM> = R<NUM> = R (the two dissection surface are equal for them to physically match and be in contact), we have
<MAT>.

<FIG> shows an exemplary lenticular incision <NUM> for extraction using the laser system <NUM>. <FIG> shows an exemplary cross-sectional view <NUM> illustrating a patient interface <NUM> (or patient interface <NUM> as shown in <FIG>), cornea <NUM>, and lenticular incision volume <NUM>, which will be referred herein as lens to be extracted. Rt and Rb are the radii of curvature for the top surface and bottom surface of a lenticular incision, respectively. ZFt (Zt) is the depth of the top surface of the lenticular incision. ZFb (Zb) is the depth of the bottom surface of the lenticular incision. The Z depths may be calculated based on the respective radii. LT is the lens thickness at the lens apex, or center thickness of the lens. ZA is depth of the lens apex. DL is the diameter of the lenticular incision, or the lens. {Z_SLOW = <NUM>} is the Z reference position before the laser system <NUM> calculates and sets Z_SLOW, e.g., {Z_SLOW = ZA + LT/<NUM>} the center depth of the lens, which remains fixed for the duration of the incision procedure. Z_SLOW may then be the reference position for the Z-scanner for top and bottom incision surfaces. In an embodiment, the diameter of the lens may be received from an operator of the laser system <NUM>, or may be calculated by the laser system <NUM>. The thickness of the lens may be determined, for example, by the total amount of correction (e.g., diopter) and the diameter of the lens.

A top view <NUM> of the lenticular incision <NUM> illustrates three exemplary sweeps (1A to 1B), (2A to 2B) and (3A to 3B), with each sweep going through (i.e., going over) the lenticular incision apex <NUM>. The incision, or cut, diameter <NUM> (DCUT) should be equal to or greater than the to-be-extracted lenticular incision diameter <NUM> (DL). A top view <NUM> shows the top view of one exemplary sweep. The lenticular incision can be performed in the following steps:.

For illustrative purposes, in a myopic correction of ΔD = <NUM> diopter (i.e., <NUM>/m), using equation (<NUM>), R = <NUM>, which is indeed much greater than the length L of the fast scan. Assuming a reasonable scan line length of L = <NUM>, using equation (<NUM>), the deviation δ ≈ <NUM>. This deviation is thus very small. For comparison purpose, the depth of focus of a one micron (FWHM) spot size at <NUM> wavelength is about ±<NUM>, meaning the length of focus is greater than the deviation δ.

<FIG> illustrates a process <NUM> of the laser system <NUM>. The laser system <NUM> may start a surgical procedure performing pre-operation measurements (Action Block <NUM>). For example, in an ophthalmologic surgery for myopic correction, the myopic diopter is determined, the SLOW_Z position is determined, and so on. The laser system <NUM> calculates the radius of curvature based on the amount of correction, e.g., the myopic correction determined in pre-operation measurements (Action Block <NUM>), as shown, for example, in equations (<NUM>) and (<NUM>) above. The laser system <NUM> calculates the diameter of the incision (Action Block <NUM>), as shown by DCUT in <FIG>. DCUT is equal to or greater than the diameter of the to-be-extracted lenticule (DL in <FIG>). The laser system <NUM> first performs side incision to provide a vent for gas that can be produced in the lenticular surface dissections, and for tissue extraction later on (Action Block <NUM>). The laser system <NUM> then performs the bottom lenticular surface dissection (Action Block <NUM>) before performing the top lenticular surface dissection (Action Block <NUM>). The lenticular tissue is then extracted (Action Block <NUM>).

The laser system <NUM> may also be used to produce other three-dimensional surface shapes, including toric surfaces for correcting hyperopia and astigmatism. The laser system <NUM> may also be used for laser material processing and micromachining for other transparent materials. Correction of hyperopia by the laser system <NUM> is discussed in detail below.

Conventional laser surgery methods to correct hyperopia utilize cut patterns including ring-shaped incision patterns that steepen the curvature of a cornea. However, <FIG> illustrates why utilizing these patterns using SMILE is impractical and unfeasible. The cross-sectional view of the cornea <NUM> in <FIG> includes a sidecut <NUM>, an upper surface cut <NUM>, lower surface cut <NUM> and a ring-shaped cut <NUM> generated by a SMILE procedure. However, the cornea <NUM> maintains an uncut annular center portion <NUM> that remains attached to an anterior portion and posterior portion of the cornea <NUM>.

This cut pattern is geometrically problematic as the clean removal of the ring cut <NUM> through the side cut <NUM> as a single ring is impeded by the center portion <NUM>. Whereas a flap provided in a LASIK procedure allows a ring shape to be easily extracted, the use of a sidecut without a flap prevents the ring-shaped stroma material from being extracted from the tunnel like incision without breaking apart. Thus, a ring-shaped lenticule is not suitable for correcting hyperopia using the SMILE procedure since the ring cut <NUM> will break up unpredictably during removal through the side cut <NUM>.

Some LASIK procedures correct hyperopia by removing cornea stroma material to increase the steepness of the cornea. For example, outward portions of the cornea are cut and removed while a center portion remains untouched except for the flap. Once the flap is folded back over, the flap fills the void vacated by the removed cornea stroma material and merges with the cornea. The cornea thus becomes steeper and a desired vision correction is achieved. However, the curve of the flap does not match the curve of the cornea such that the merger of the flap and cornea creates folds in the stroma that increase light scattering and create undesirable aberrations.

The embodiments described herein overcome these limitations. <FIG> illustrates an exemplary lenticular incision <NUM> that steepens the cornea by cutting and removing a symmetric concave lens-shaped stroma material from a cornea <NUM>. From an optical focus power perspective, the concave shape of the lenticule <NUM> is equivalent to steepening the cornea or adding a convex lens in front of the eye.

Furthermore, extraction of the lenticule <NUM> as a whole piece through a sidecut incision <NUM> is assured and improved over a ring-shape cut, or a tunnel-like cut, or a toric cut. The incision includes a peripheral portion <NUM> or tapering portion providing ideal merging of the cornea after the lenticule <NUM> is extracted without folding in a top surface or bottom surface.

<FIG> illustrates an exemplary lenticular incision <NUM> using a surgical ophthalmic laser system according to an embodiment of the present invention. For example, SMILE techniques may be applied in conjunction with <FIG> to treat hyperopia using a sub-nanosecond laser. A cross-sectional view <NUM> and top view <NUM> are provided of the lenticule cuts <NUM>, <NUM> and side cut <NUM>. In <FIG>, a patient interface <NUM> is pressed against a cornea <NUM>. The lenticular incision includes a bottom lens surface <NUM> and a top lens surface <NUM>. The bottom surface <NUM> includes a radius of curvature R1 and the top surface <NUM> includes a radius of curvature R2.

A side cut <NUM> is performed first to provide a path for gas to vent to prevent the formation of bubbles. A bottom surface cut <NUM> is then performed prior to performing a top surface cut <NUM> to prevent the cutting beam from being blocked by bubbles generated by previous cornea dissection. The top and bottom surface cuts each include a central portion and a peripheral portion. The central portions are concave while the peripheral portions of the top and bottom cuts tapers (diminishes) towards each other to meet. The tapering peripheral portions minimize light scattering at the edges and further optimizes the matching of the cut surfaces and prevent folding after the lenticule has been removed.

As shown in <FIG>, the thickest portion of the cut is provided at the boundary of the taper portion and the concave portion. For the top and bottom surfaces to match after lens extraction, the bottom and top surfaces are preferably mirror symmetric about a plane <NUM>.

These exemplary lenticular incisions allow lenticular tissue to be extracted in a single unbroken piece through the sidecut. The taper of the peripheral portions allows smooth extraction through the sidecut as a gradual slope is provided. The peripheral portions also support the merging of the top and bottom portions of the cornea as a top surface and bottom surface compress back together to form a smooth merge. Without a taper to the peripheral portions, the apex of the central portions would never merge and would form a permanent gap.

A concave lens cut includes a top concave lenticular incision and a bottom concave lenticular incision of a lens in the subject's eye. The concave lens cut may include at least one of a spherical surface. , a cylindrical component, and any high order component. The top concave lenticular incision and the bottom concave lenticular incision may be mirror symmetric or nearly mirror symmetric to each other so long as the merging of the top surface and bottom surface does not create folding.

The system may operate with a laser having a wavelength in a range between <NUM> nanometer and <NUM> nanometer and a pulse width in a range between <NUM> femtosecond and <NUM> nanosecond.

In prior art solutions, a top layer cut is longer than a bottom layer cut. Under this configuration, the top and bottom cornea portions do not ideally merge as the top surface must fold in and compress in order to merge with shorter layer cut. With this fold created by the dissection, light scattering is increased. In contrast, a mirror symmetric cut along a center line allows ideal merge with no folding between a top layer and bottom layer. Consequently, there is less light scattering.

A lens edge thickness is given by δE, δE1, δE2. A lens depth H is given as a distance between an anterior of the cornea <NUM> and the plane <NUM>. The bottom surface <NUM> and top surface <NUM> have a lens diameter DL, a lens center thickness δc and a shape defined by respective curves Z<NUM>,L(x,y) and Z<NUM>,L(x,y). In order to minimize the amount of dissected cornea stroma material removed, the central thickness δc should be minimized. For example, the central thickness may be a few µm, which can be achieved by using a laser beam with a high numerical aperture (such as NA = <NUM>).

Each of the bottom lens surface cut <NUM> and the top lens surface cut <NUM> includes a tapering zone <NUM> along a periphery of the cuts. The tapering zone <NUM> is defined by a tapering zone width ξ and the curves Z<NUM>,T(x,y) and Z<NUM>,T(x,y).

A sidecut <NUM> is provided from a surface of the cornea to the tapering zone <NUM> for removal of the lenticule. The sidecut may meet the tapering zone <NUM> on the mirror plane <NUM> or other suitable extraction point.

With these parameters as described and illustrated, a set of equations are provided below that determine the three-dimensional shape of the lenticular cuts, assuming that the desired correction is purely defocus: <MAT> <MAT> <MAT> <MAT><MAT><MAT>.

The shape and dimensions of the cuts may include additional correction for higher order aberrations and may be computed from measured vision errors. In some cases, approximately <NUM>% of the total hyperopic correction is applied to each of the two mutually mirror-imaged cut surfaces.

It is noted that the thickest portion of the concave lens cut is provided at the intersection of the tapering zone and the concave lens cuts which correspond to a portion of the cornea that is thicker than a center portion of the cornea. Consequently, from the standpoint of cornea thickness, correcting hyperopia is more tolerable than correcting myopia, where the thicker portion of the lens to be removed is at the center of the cornea, corresponding to a thinner portion of the cornea.

The shape of the tapering zone <NUM> need not be linear in shape. The tapering zone may be curved or any shape that minimizes light scattering at the cutting junctions and optimizes the matching of the two cut surfaces after lens extraction. The peripheral zone may be linear or a higher order polynomial.

Femtosecond laser systems and UV <NUM> sub-nanosecond lasers may be used to create cornea incisions.

For illustrative purposes, Equations (<NUM>), (<NUM>) and (<NUM>) are used to estimate the thickness of the concave lens. In a hyperopic correction of ΔD = <NUM> diopter (which is high end values for LASIK hyperopia procedures) and assuming that a symmetric shape of the lenticule is selected, R<NUM> = R<NUM> = <NUM>. Assuming DL = <NUM> and δC = <NUM>, then δE = δE1 + δE2 ≈ δC + DL<NUM>·ΔD/[<NUM>(n-<NUM>)] ≈ <NUM>.

<FIG> illustrates an exemplary scanning process <NUM> using a surgical ophthalmic laser system. <FIG> illustrates another example of the "Fast-Scan-Slow-Sweep" scanning described previously. While performing an XY scan, Z values can be calculated from Eqs. (<NUM>)-(<NUM>), and the desired three-dimensional concave lens-shape cutting surfaces may be generated.

A top view of the lenticular incision illustrates three exemplary sweeps <NUM> (1A to 1B), (2A to 2B) and (3A to 3B), with each sweep going through (i.e., going over) the concave lenticular incision <NUM> and tapering zone <NUM>. The lenticular incision can be performed in the following steps:.

Certain example parameters for using the femtosecond laser in intra-stromal corneal incisions may improve results. Using the laser described herein outside of the laser parameters described below may result in undesirable consequences such as melted corneal tissue or tissue bridges left in cutting beds even after treatment. Neither of these effects are desirable, and by utilizing the parameters below, with the femtosecond laser described above, results may be reached for treatment which avoid these effects. Thus, using the parameters here, the laser may be used to create a smooth incision in the cornea and improve treatment.

As discussed above, the femtosecond laser beam may be directed into an intrastromal corneal layer of a patient for treatment. The system may pre-compensate dispersion of the laser beam path so as to focus the laser beam into a focal point to disrupt cells in the intrastromal corneal layer. This laser beam focus may be moved to create a pattern of spaced focal points inside the intrastromal corneal layer thus incising a lens with the spaced focal points. And as the xy scan pattern is continuous in the systems described above, oscillating the beam in a given distance producing a scan line for treatment. The z depth of the focal points may be adjusted along with the xy position to allow the oscillating beam to incise the cornea.

<FIG> illustrates an example pattern <NUM> of focused laser <NUM> spots <NUM>. The example of <FIG> shows a cornea <NUM> being treated as described herein, but the tissue that is treated could be any kind of tissue in the eye or elsewhere on the body.

It should be noted that all of the parameters listed below are specific to the laser beam at the spot focus <NUM> itself. In other words, the laser beam may have different parameters within the laser system or within the various focus sub systems. These parameters listed below pertain to the focused laser beam spot at the treatment point.

Wavelength - wavelength of the femtosecond laser described above can be between <NUM> and <NUM>. A preferred embodiment is between <NUM> and <NUM>.

Spot size - in diameter, spot size of each individually focused laser beam focal spot could be between <NUM> and <NUM>. A preferred spot size is near <NUM> in diameter.

Spot spacing - spot spacing of each individually focused laser beam focal spot, from center to center of individual spots, could be between. <NUM> and <NUM>. In certain preferred embodiments, a spot spacing of less than <NUM> is used.

In the above examples, a laser beam focal spot size of <NUM> in diameter combined with a laser beam focal spot spacing of less than <NUM> results in overlapping spots. And as the laser beam focal spot causes tissue disruption in a cornea, for example, forming a bubble in the tissue, the bubbles may be even greater than <NUM> in diameter and overlap as well. Using the example laser and laser parameters described here, however, this overlapping of focal spots and bubbles is an acceptable spacing and spot size because of the energy parameters used. Overlapping focal spots using other lasers, or lasers with different parameters may result in excessive power into the eye, melting of tissue and other less desired effects.

Frequency - The system may utilize a laser beam having a frequency between <NUM> and <NUM>. An example embodiment is a laser beam with a frequency of <NUM>. Another example embodiment is <NUM>.

Some example embodiments include using a resonant scanner to produce a scan line. In some examples the resonant scanner continuously scans while the laser system is in operation. Example frequencies for such a scan may be between <NUM>,<NUM> and <NUM>,<NUM>. Some example embodiments use <NUM>,<NUM>.

Pulse width - the femtosecond laser described above may have a pulse width between <NUM> fs and <NUM> fs. A preferred embodiment is between <NUM> and <NUM> femtoseconds. A pulse width below <NUM> femtoseconds may produce optimal results.

In some embodiments, dispersion compensation may be used to achieve short pulse width at the focal point of the laser beam. Such dispersion compensation may include a glass compressor to introduce negative chirp.

Energy - the femtosecond laser described above has a smaller pulse width but higher peak power than other lasers currently available. But in comparison, the femtosecond laser total power may be less than other lasers with wider pulse width and lower peak power. Energy used in one spot may be between <NUM> nJ and <NUM> nJ. One example embodiment is between <NUM> nJ and <NUM> nJ.

<FIG> is a flowchart illustrating an exemplary surgery process <NUM>. At the treatment site, the laser system is first set to limit the amount of total energy for an individual spot to around <NUM> nJ <NUM>. Next, at the treatment site, the wavelength of the laser is set to between <NUM> and <NUM> <NUM>. Next, at the treatment site, the frequency of the laser is set to <NUM> <NUM>. Next, at the treatment site, the laser pulse width is set to between <NUM> and <NUM> femtoseconds <NUM>. Next, at the treatment site, spots are created that are <NUM> in diameter <NUM>. Finally, at the treatment site, the spots are spaced apart less than <NUM> <NUM>.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The term "connected" is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate some embodiments and does not pose a limitation unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the embodiments.

Claim 1:
A system for delivering laser treatment into a cornea of an eye, the system comprising:
a laser (<NUM>) capable of generating a pulsed laser beam (<NUM>) and a delivery system configured to deliver the pulsed laser beam (<NUM>) to a target in the cornea of the eye;
an XY-scan device to move the scan line;
a Z-scan device to modify a Z location of a focus of the pulsed laser beam in a z direction along an optical axis; and
a controller configured to control the XY-scan device and the Z-scan device to focus the pulsed laser beam into a pattern of spaced focal spots that form a top lenticular incision and a bottom lenticular incision of a lens in the eye;
wherein the focal spots have a diameter between <NUM> and <NUM>;
characterized in that the spaced focal spots in the pattern overlap.