Patent Application
20180008461
Embodiments of this invention relate generally to laser-assisted ophthalmic procedures, and more particularly, to systems and methods for making lenticular incisions in the cornea based on wavefront-guided measurements.
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 10 femtoseconds and as long as 3 nanoseconds, and a wavelength between 300 nm and 3000 nm. 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 OptiMedica's 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 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 current laser surgery treatments that correct hyperopia using LASIK and PRK, 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. In a LASIK procedure, a flap is created, and then lifted up so that 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. Instead, an excimer laser is used to first remove the epithelium layer and then the ring-shaped stroma material. The epithelium layer grows back a few days following the 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.
Further, as shown in
Typically, the manifest refraction method was used to measure the eye to calculate the necessary correction of aberrations. Such measurements, however, may have inherent disadvantages in that the error rate can be high, higher order aberrations are not measured and/or corrected for, and with manifest refraction, no objective reference exists for the lateral position of lenticule incisions.
Therefore, there is a need for improved systems and methods for measuring for correction as well as for generating corneal lenticular incisions for vision correction using high repetition rate femtosecond lasers.
Hence, to obviate one or more problems due to limitations and disadvantages of the related art, this disclosure provides embodiments including an ophthalmic surgical laser system comprising a laser delivery system for delivering a 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 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.
Other embodiments disclose an ophthalmic surgical laser system comprising a laser delivery system for delivering a 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 concave lenticular incision and a bottom concave lenticular incision of a lens on the subject's eye.
Certain example systems and methods of performing ophthalmic surgery are disclosed here, including, obtaining a wavefront map by a wavefront aberrometer, calculating an ablation depth map to create a lenticule in a cornea, using the wavefront map, wherein the ablation depth map includes refractive correction, obtaining a femto target by adjusting the wavefront target thickness, performing femto treatment planning, performing side cut by a femtosecond pulsed laser, performing bottom surface incision by the femtosecond pulsed laser; and performing top surface incision by the femtosecond pulsed laser.
Systems and method of performing ophthalmic surgery, comprising, obtaining a wavefront map of a free eye by a wavefront aberrometer to measure a refractive error, obtaining an iris image for the free eye, determining a cutting profile to cut in a cornea of the eye, based on the wavefront aberrometer measurement, docking the eye to a patient interface of an ultrashort pulsed laser, obtaining an iris image for the docked eye, determining a translation of the cutting profile for the docked eye using the iris image for the docked eye compared to the iris image of the free eye, and incising, by the ultrashort pulsed laser, a bottom surface incision based on the translated cutting profile on the docked eye. Alternatively or additionally, incising, by the ultrashort pulsed laser, a top surface incision based on the translated cutting profile on the docked eye. Alternatively or additionally, the ultrashort laser is at least one of a picosecond, femtosecond, or nanosecond laser. Alternatively or additionally, the cutting profile includes a lenticule shape. Alternatively or additionally, the cutting profile includes at least one of a transition profile or an entry incision for removal of the lenticule. Alternatively or additionally, incising the transition profile and incising the entry incision for lenticule removal. Alternatively or additionally, the transition profile is an internal side cut. Alternatively or additionally, the transition profile is a continuation of the bottom surface incision and the top surface incision. Alternatively or additionally, the entry side incision has an arc length between 1 mm and 10 mm. Alternatively or additionally, an apex of the lenticule and an apex of the cornea is between 60 μm and 200 μm. Alternatively or additionally, the lenticule has a lateral diameter between 4 mm and 8 mm. Alternatively or additionally, the patient interface that contacts the patient cornea is flat. Alternatively or additionally, the patient interface that contacts the patient cornea is curved. Alternatively or additionally, the patient interface that contacts the patient cornea is liquid. Alternatively or additionally, the ultrashort pulsed laser has a pulse width between 10 fs and 5 ns. Alternatively or additionally, the ultrashort pulsed laser has a wavelength spectrum centered at between 320 nm and 1200 nm. Alternatively or additionally, the ultrashort pulsed laser has a pulse width between 80 fs and 250 fs. Alternatively or additionally, the ultrashort pulsed laser has a wavelength spectrum centered at between 1020 nm and 1070 nm. Alternatively or additionally, the refractive error is myopia with or without astigmatism. Alternatively or additionally, the refractive error is hyperopia with or without astigmatism. Alternatively or additionally, the refractive error is mixed astigmatism. Alternatively or additionally, the refractive error includes higher order aberrations. Alternatively or additionally, the lenticule includes an added thickness, beyond what is needed to correct the refractive error. Alternatively, or additionally, the lenticule, before the added thickness, is less than 40 μm. Alternatively, and/or additionally, the determining a translation of the cutting profile step includes accounting for cyclotorsion rotation. Alternatively or additionally, the iris image is taken with at least one of white light illumination or infrared illumination.
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 embodiments 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, 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.
Embodiments here are generally directed to systems and methods for laser-assisted ophthalmic procedures, and more particularly, to systems and methods for lenticular laser incisions.
Referring to the drawings,
In some embodiments, the system 10 uses a pair of scanning mirrors or other optics (not shown) to angularly deflect and scan the pulsed laser beam 18. For example, scanning mirrors driven by galvanometers may be employed where each of the mirrors scans the pulsed laser beam 18 along one of two orthogonal axes. A focusing objective (not shown), whether one lens or several lenses, images the pulsed laser beam 18 onto a focal plane of the system 10. The focal point of the pulsed laser beam 18 may thus be scanned in two dimensions (e.g., the x-axis and the y-axis) within the focal plane of the system 10. 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 14 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 some embodiments, the laser 14 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 10 may be used to photoalter a variety of materials (e.g., organic, inorganic, or a combination thereof), in some embodiments, the laser system 10 is suitable for ophthalmic applications. In these cases, the focusing optics direct the pulsed laser beam 18 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 10 may also include a lens to change the shape (for example, flatten or curve) of the cornea prior to scanning the pulsed laser beam 18 toward the eye.
The laser system 10 is capable of generating the pulsed laser beam 18 with physical characteristics similar to those of the laser beams generated by a laser system disclosed in U.S. Pat. No. 4,764,930, U.S. Pat. No. 5,993,438, U.S. patent application Ser. No. 12/987,069, filed Jan. 7, 2011, filed Jan. 7, 2011 (published as US20110172649), U.S. patent application Ser. No. 13/798,457 filed Mar. 13, 2013 (published as US20140104576), U.S. patent application Ser. No. 14/848,733, filed Sep. 9, 2015, U.S. patent application Ser. No. 14/865,396, filed Sep. 25, 2015, U.S. patent application Ser. No. 14/968,549, filed Dec. 14, 2015, and U.S. patent application Ser. No. 14/970,898, filed Dec. 16, 2015, which are incorporated herein by reference as if fully set forth.
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 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 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 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 22 to a user.
Storage subsystem 56 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 methods of the present embodiments, 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. File storage subsystem 60 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 22. The modules implementing the functionality of the present embodiments may be stored by file storage subsystem 60.
Bus subsystem 54 provides a mechanism for letting the various components and subsystems of controller 22 communicate with each other as intended. The various subsystems and components of controller 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.
Due to the ever-changing nature of computers and networks, the description of controller 22 depicted in
As should be understood by those of skill in the art, additional components and subsystems may be included with laser system 10. 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, which is incorporated herein by reference. 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 U.S. Pat. No. 4,665,913, U.S. Pat. No. 4,669,466, U.S. Pat. No. 4,732,148, U.S. Pat. No. 4,770,172, U.S. Pat. No. 4,773,414, U.S. Pat. No. 5,207,668, U.S. Pat. No. 5,108,388, U.S. Pat. No. 5,219,343, U.S. Pat. No. 5,646,791, U.S. Pat. No. 5,163,934, U.S. Pat. No. 8,394,084, U.S. Pat. No. 8,403,921, U.S. Pat. No. 8,690,862, U.S. Pat. No. 8,709,001, U.S. application Ser. No. 12/987,069, filed Jan. 7, 2011, U.S. patent application Ser. No. 13/798,457 filed Mar. 13, 2013 (published as US20140104576), U.S. patent application Ser. No. 14/848,733, filed Sep. 9, 2015, U.S. patent application Ser. No. 14/865,396, filed Sep. 25, 2015, U.S. patent application Ser. No. 14/968,549, filed Dec. 14, 2015, and U.S. patent application Ser. No. 14/970,898, filed Dec. 16, 2015, which are incorporated herein by reference.
In one embodiment, the laser surgery system 10 includes a femtosecond oscillator-based laser operating in the MHz range, for example, 10 MHz, for example, from several MHz to tens of MHz. For ophthalmic applications, the XY-scanner 28 may utilize a pair of scanning mirrors or other optics (not shown) to angularly deflect and scan the pulsed laser beam 18. For example, scanning mirrors driven by galvanometers may be employed, each scanning the pulsed laser beam 18 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 10. The focal point of the pulsed laser beam 18 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 10. 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. In many embodiments, the XY-scanner 28 deflects the pulse laser beam 18 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 21 of
In another embodiment shown in
where R is greater than L. R is the radius of curvature of the surface dissection 720, 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
where n=1.376, which is the refractive index of cornea, and R1 and R2 (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 R1=R2=R (the two dissection surface are equal for them to physically match and be in contact), we have
In an embodiment,
A top view 850 of the lenticular incision 800 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 855. The incision, or cut, diameter 857 (DCUT) should be equal to or greater than the to-be-extracted lenticular incision diameter 817 (DL). A top view 880 shows the top view of one exemplary sweep. In an embodiment, the lenticular incision is performed using the following steps:
1. Calculate the radius of curvature based on the amount of correction, e.g., a myopic correction.
2. Select the diameter for the lenticular incision to be extracted.
3. Perform the side incision first (not shown) to provide a vent for gas that can be produced in the lenticular surface dissections. This is also the incision for the entry of forceps and for lens extraction.
4. Perform bottom surface dissection (the lower dissection as shown in cross-sectional view 810). In doing so, the fast scan line is preferably kept tangential to the parallels of latitude, and the trajectory of the slow sweep drawn by X, Y, and Z scanning devices moves along the meridians of longitude (near south pole in a sequence of 1A→1B (first sweep of lenticular cut), 2A→2B (second sweep of lenticular cut), 3A→3B (third sweep of lenticular cut), and so on, until the full bottom dissection surface is generated.
5. Perform the top surface dissection (the upper dissection as shown in the cross-sectional view 810) in a similar manner as the bottom dissection is done. The bottom dissection must be performed first. Otherwise, the bubble generated during the top dissection will block the laser beam from making the bottom dissection.
For illustrative purposes, in a myopic correction of ΔD=10 diopter (i.e., 1/m), using equation (3), R=75.2 mm, which is indeed much greater than the length L of the fast scan. Assuming a reasonable scan line length of L=1 mm, using equation (1), the deviation δ≈1.7 μm. This deviation is thus very small. For comparison purpose, the depth of focus of a one micron (FWHM) spot size at 1 μm wavelength is about ±3 μm, meaning the length of focus is greater than the deviation δ.
In other embodiments, the laser system 10 may also be used to produce other three-dimensional surface shapes, including toric surfaces for correcting hyperopia and astigmatism. The laser system 10 may also be used for laser material processing and micromachining for other transparent materials. Correction of hyperopia by the laser system 10 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. In the SMILE procedure illustrated in
However,
This cut pattern is geometrically problematic as the clean removal of the ring cut 1170 through the side cut 1120 as a single ring is impeded by the center portion 1180. Whereas a flap provided in a LASIK procedure allows a ring shape to be easily extracted, the use of a side cut 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 1170 will break up unpredictably during removal through the side cut 1120.
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.
Furthermore, extraction of the lenticule 1220 as a whole piece through a side cut incision 1210 is assured and improved over a ring-shape cut, or a tunnel-like cut, or a toric cut. The incision includes a peripheral portion 1230 or tapering portion providing ideal merging of the cornea after the lenticule 1220 is extracted without folding in a top surface or bottom surface.
A side cut 1350 is performed first to provide a path for gas to vent to prevent the formation of bubbles. A bottom surface cut 1310 is then performed prior to performing a top surface cut 1320 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 in a circumferential ring or edge. 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
These exemplary lenticular incisions allow lenticular tissue to be extracted in a single unbroken piece through the side cut. The taper of the peripheral portions allows smooth extraction through the side cut 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 350 nanometers and 1100 nanometers, and a pulse width in a range between 10 femtoseconds and 1 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 1306 and the plane 1360. The bottom surface 1310 and top surface 1320 have a lens diameter DL, a lens center thickness δc and a shape defined by respective curves Z1,L(x,y) and Z2,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=0.6).
Each of the bottom lens surface cut 1310 and the top lens surface cut 1320 includes a tapering zone 1330 along a periphery of the cuts. The tapering zone 1330 is defined by a tapering zone width ξ and the curves Z1,T(x,y) and Z2,T(x,y).
A side cut 1350 is provided from a surface of the cornea to the tapering zone 1330 for removal of the lenticule. The side cut may meet the tapering zone 1330 on the mirror plane 1360 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:
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 embodiments, approximately 50% 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 1330 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.
Some embodiments apply to single-spot scanning methods applied in femtosecond laser systems. The embodiments also apply to cornea incisions using UV 355 nm sub-nanosecond lasers.
For illustrative purposes, Equations (2), (8) and (9) are used to estimate the thickness of the concave lens. In a hyperopic correction of ΔD=5 diopter (which is high end values for LASIK hyperopia procedures) and assuming that a symmetric shape of the lenticule is selected, R1=R2=150.4 mm. Assuming DL=7.0 mm and δC=10 μm, then δE=δE1+δE2≈δC+DL2·ΔD/[8(n−1)]≈92 μm.
A top view of the lenticular incision illustrates three exemplary sweeps 1430 (1A to 1B), (2A to 2B) and (3A to 3B), with each sweep going through (i.e., going over) the concave lenticular incision 1410 and tapering zone 1420. In an embodiment, the lenticular incision is performed in the following steps:
1. Calculate the radius of curvature based on the amount of correction, e.g., a hyperopic correction.
2. Select the diameter for the lenticular incision to be extracted.
3. Calculate the shape of the lenticular incisions (concave surface and taper).
4. Perform the side incision first (not shown) to provide a vent for gas that can be produced in the lenticular surface dissections. This is also the incision for the entry of forceps and for lens extraction.
5. Perform bottom surface dissection (the bottom dissection 1310 as shown in cross-sectional view). In doing so, the fast scan line is preferably kept tangential to the parallels of latitude, and the trajectory of the slow sweep drawn by X, Y, and Z scanning devices moves along the meridians of longitude (near south pole in a sequence of 1A→1B (first sweep of lenticular cut), 2A→2B (second sweep of lenticular cut), 3A→3B (third sweep of lenticular cut), and so on (4A), until the full bottom dissection surface is generated.
6. Perform the top surface dissection 1320 in a similar manner as the bottom dissection is done. It is noted that the bottom dissection is done first. Otherwise, the bubble generated during the top dissection will block the laser beam in making the bottom dissection.
Wavefront Map Guided Lenticular Incisions
Previously, manifest refraction measurements were used to determine the femtosecond laser parameters to form a lenticule in a cornea. However, such measurements may have inherent disadvantages. For example, error may be large, the higher order aberrations may not be measured and therefore not corrected for.
Using some other measurement, such as a wavefront map of a patient's eye which measures aberrations of light that pass through the cornea and lens, a lenticular shape may be determined. Such wavefront guided measurements may be more precise, up to +/−0.01D, and higher order aberrations may be measured and corrected. Iris imaging may be used for positioning/aligning the laser system to the eye to account for such things as cyclorotation when a patient lies in a supine position for treatment. Iris imaging may also be used for patient registration and recognition.
In a high level example, the system may be used to measure a pupil diameter to calculate a theoretical perfect eye map with the same pupil size and also capture an image of the iris.
Next, the system may capture the round shave wavefront from the eye, the light reflected from the retina and after back through the pupil.
Next, the system may map any captured aberrations and compare them to the theoretical perfect eye map. The comparison may be used to determine corrections that need to be made and that information may be used to incise a lenticule in the patient cornea with the femtosecond pulsed lasers described here.
Aberrations
Old manifest refraction could measure and correct for low order aberrations such as sphere and cylinder which may be corrected for using glasses. But there are many higher-order aberrations including Zernike coefficients, circle aberrations, spherical aberration, coma and trefoil. The wavefront guided systems here may correct for some or all of these higher order aberrations as they may be measured by the wavefront system.
For example, spherical aberration is the cause of dark condition myopia and may result in the patient experiencing visualized halos around lights. In light conditions, peripheral rays may be blocked when the pupil constricts, lessening the halo effect. In dark conditions, peripheral rays may not be blocked when the pupil is enlarged causing a slight myopia. Other aberrations include Coma and Trefoil.
These higher order aberrations may be detected, analyzed and used to determine a treatment using the systems and methods described here. Other aberrations such as asymmetrical aberrations may also be measured and corrected using the systems and methods here. For example, a previous off-center surgery may result in an eye with asymmetrical correction. Using the systems and methods here, that asymmetry may be measured and an asymmetrical lenticule may be incised to compensate.
Certain example embodiments may be used to not remove every aberration but to strategically leave certain aberrations to compensate for other optical corrections that are not otherwise correctable. On top of the wavefront error, certain things may be added back to accomplish a goal. For example, to extend depth of focus, you may wish to leave a circular aberration so that a person with presbyopia, a condition where the lens of the eye is no longer able to adjust for near focus, can minimally compromise their far sight but also correct for near sight.
Steps to Use Wavefront Guided Lenticular Incisions
Step-1510: Obtain Wavefront Target. In this step, a wavefront map is measured of an eye and an iris image is taken for the eye under its natural, non-accommodative, far vision condition. Nomogram adjustment and physician adjustment may be applied to determine the ablation depth map 1512, or Wavefront Target, which is to be removed from the cornea to achieve the desired vision correction.
Step-1520: Obtain Femto Target. Since a too thin lenticule 1522 may be difficult to extract from a cornea, it may be useful to add a constant, non-refractive depth 1524 to the determined Wavefront Target, if its maximum depth is less than, 40 μm, for example. And, if the Wavefront Target is too thick so the residual stroma bed is less than 250m, a reduction in thickness may be made by reducing the diameter of the optical zone and removing a constant, non-refractive depth from the Wavefront Target. The thickness adjusted (or intact) target may be referred to as the Femto Target, which is the desired tissue shape to remove from the cornea. It should be noted that non-refractive depth, are not defined by two concentric spherical surfaces. Rather, it is a small, constant z-displacement for the anterior cornea surface in the optical zone, so the cornea shape and refractive power remain unchanged after the displacement.
Step-1530: Obtain Femto Iris Image. Next, when the patient is gazing at the fixation light and when the patient interface is in close proximity (but not in contact) to the cornea, an iris image may be made. This image 1532, 1534 may be used to map areas of the iris for alignment purposes and/or identification purposes. Note: the deformation of eye under applanation will be taking into account by Step-1540.
Step-1540: Perform Femto Treatment Planning which may include several sub-steps. A) Perform Iris Registration and Cyclotorsion Correction for alignment purposes. B) Transform Femto Target to Femto Cut Profile. The shape of a lenticule in cornea under applanation is different from that in a free cornea, therefore, the Femto Target may be transformed into a Femto Cut Profile for the cornea shape when the system is docked to it 1542. C) Complete Femto Treatment Planning to integrate Femto Cut Profile, Transition Zone to taper the lenticule for extraction, Entry Side Cut, and possibly another Internal Side Cut, to achieve optimum precision and accuracy of the lenticule shape, easy lenticule release, minimum total laser pulse energy, and shorter cutting time.
The laser system 10 may be used to perform a side incision to provide a vent for gas that can be produced in the lenticular surface dissections, and for tissue extraction later on 1550. The laser system 10 then performs the bottom lenticular surface dissection 1560 before performing the top lenticular surface dissection 1570. Performing the dissections in this order allows gas to vent out of the cornea instead of becoming trapped in gas bubbles within the cornea. The lenticular tissue may then be extracted 1580.
Wavefront Aberrometer Systems
The wavefront aberrometer subsystem 16150 of the assembly 16100 includes a light source 16152 providing a probe beam and a wavefront sensor 16155. The Wavefront aberrometer subsystem 16150 preferably further comprises a collimating lens 16154, a polarizing beam splitter 16156, an adjustable telescope comprising a first optical element, lens 16163 and a second optical element, lens 16164, a movable stage or platform 16166, and a dynamic-range limiting aperture 16165 for limiting a dynamic range of light provided to wavefront sensor 16155 so as to preclude data ambiguity. Light from the wavefront aberrometer subsystem may be directed to one of the constituent optical elements of the optical system 16170 disposed along a central axis 16102 passing through the opening or aperture 16114 of the structure 16110. It will be appreciated by those of skill in the art that the lenses 16163, 16164, or any of the other lenses discussed herein, may be replaced or supplemented by another type of converging or diverging optical element, such as a diffractive optical element.
Light source 16152 is preferably an 840 nm SLD (super luminescent laser diode). An SLD is similar to a laser in that the light originates from a very small emitter area. However, unlike a laser, the spectral width of the SLD is very broad, about 40 nm. This tends to reduce speckle effects and improve the images that are used for wavefront measurements.
Preferably, wavefront sensor 16155 is a Shack-Hartmann wavefront sensor comprising a detector array and a plurality of lenslets for focusing received light onto its detector array. In that case, the detector array may be a CCD, a CMOS array, or another electronic photosensitive device. However, other wavefront sensors may be employed instead. Embodiments of wavefront sensors which may be employed in one or more systems described herein are described in U.S. Pat. No. 6,550,917, issued to Neal et al. on Apr. 22, 2003, and U.S. Pat. No. 5,777,719, issued to Williams et al. on Jul. 7, 1998, both of which patents are hereby incorporated herein by reference in their entirety.
The aperture or opening in the middle of the group of first light sources 16120 (e.g., aperture 16114 in principal surface 16112 of structure 16110) allows system 16100 to provide a probe beam into eye 16101 to characterize its total ocular aberrations. Accordingly, third light source 16152 supplies a probe beam through a light source polarizing beam splitter 16156 and polarizing beam splitter 16162 to first beam splitter 16172 of optical system 16170. First beam splitter 16172 directs the probe beam through aperture 16114 to eye 16101. Preferably, light from the probe beam is scattered from the retina of eye 16100, and at least a portion of the scattered light passes back through aperture 16114 to first beam splitter 16172. First beam splitter 16172 directs the back scattered light back through beam splitter 16172 to polarizing beam splitter 16162, mirror 16153 to wavefront sensor 16155.
Wavefront sensor 16155 outputs signals to a processor of controller 60 which uses the signals to determine ocular aberrations of eye 16101. Preferably, processor 16141 is able to better characterize eye 16101 by considering the corneal topography of eye 16101 measured by the corneal topography subsystem, which may also be determined by processor 16141 based on outputs of detector array 16141, as explained above.
In operation of the wavefront aberrometer subsystem 16150, light from light source 16152 is collimated by lens 16154. In polarization embodiments, the light passes through light source polarizing beam splitter 16156. The light entering light source polarizing beam splitter 16156 is partially polarized. Light source polarizing beam splitter 16156 reflects light having a first, S, polarization, and transmits light having a second, P, polarization so the exiting light is 100% linearly polarized. In this case, S and P refer to polarization directions relative to the hypotenuse in light source polarizing beam splitter 16156.
Light from light source polarizing beam splitter 16156 enters polarizing beam splitter 16162. The hypotenuse of polarizing beam splitter 16162 is rotated 90 degrees relative to the hypotenuse of light source polarizing beam splitter 16156 so the light is now S polarized relative the hypotenuse of polarizing beam splitter 16162 and therefore the light reflects upwards. The light from polarizing beam splitter 16162 travels upward and passes through toward beam splitter 16172, retaining its S polarization, and then travels through quarter wave plate 16171. Quarter wave plate 16171 converts the light to circular polarization. The light then travels through aperture 16114 in principal surface 16112 of structure 16110 to eye 16101. Preferably, the beam diameter on the cornea is between 1 and 2 mm. Then the light travels through the cornea and focuses onto the retina of eye 16100.
The focused spot of light becomes a light source that is used to characterize eye 16100 with wavefront sensor 16155. Light from the probe beam that impinges on the retina of eye 101 scatters in various directions. Some of the light reflects back as a semi-collimated beam back towards assembly 16100. Upon scattering, about 90% of the light retains its polarization. So the light traveling back towards assembly is substantially still circularly polarized. The light then travels through aperture 16114 in principal surface 16112 of structure 16110, through quarterwave plate 16171, and is converted back to linear polarization. Quarterwave plate 16171 converts the polarization of the light from the eye's retina so that it is P polarized, in contrast to probe beam received from third light source 16150 having the S polarization. This P polarized light then reflects off of first beam splitter 16172, and then reaches polarizing beam splitter 16162. Since the light is now P polarized relative the hypotenuse of polarizing beam splitter 16162, the beam is transmitted and then continues onto mirror 16153. After being reflected by mirror 16153, light is sent to an adjustable telescope comprising a first optical element 16164 and a second optical element (e.g., lens) 16163 and a movable stage or platform 16166. The beam is also directed through a dynamic-range limiting aperture 16165 for limiting a dynamic range of light provided to wavefront sensor 16155 so as to preclude data ambiguity.
When wavefront sensor 16155 is a Shack-Hartmann sensor, the light is collected by the lenslet array in wavefront sensor 16155 and an image of spots appears on the detector array (e.g., CCD) in wavefront sensor 16155. This image is then provided to a process of the controller 60 and analyzed to compute the refraction and aberrations of eye 16101.
Iris Imaging
The optical measurement systems according to the present invention preferably include an iris imaging subsystem 40 used to properly align the system during measurements and treatment. The imaging subsystem 40 generally comprises an infrared light source, preferably infrared light source 152, and detector 141. In operation light from the light source 152 is directed along second optical path 160 to first optical path 170 and is subsequently directed to eye 101 as described above. Light reflected from the iris of eye 101 is reflected back along first optical path 170 to detector 141. In normal use, an operator will adjust a position or alignment of system 100 in XY and Z directions to align the patient according to the image detector array 141. In one embodiment of the iris imaging subsystem, eye 101 is illuminated with infrared light from light source 152. In this way, the wavefront obtained by wavefront sensor 155 will be registered to the image from detector array 141.
The image that the operator sees is the iris of eye 100. The cornea generally magnifies and slightly displaces the image from the physical location of the iris. So the alignment that is done is actually to the entrance pupil of the eye. This is generally the desired condition for wavefront sensing and iris registration.
Preferably, the OCT subsystem 190 provides sufficiently resolved structural information to provide a structural assessment that may provide a user with an indication of suitability of a particular patient for a laser cataract procedure. In some embodiments, an OCT scan performed by the OCT subsystem 190 at or near the retina (i.e., a retina scan) is sufficiently resolved to identify the foveal pit location and depth, wherein a lack of depression indicates an unhealthy retina.
In some embodiments, the optical measurement instrument of the present invention provides one or more measurements sufficient to provide an assessment of the tear film of a patient. In one embodiment, the tear film assessment comprises a comparison of a wavefront aberrometry map and a corneal topography map or OCT map of the patient's eye, by, for instance, determining the irregular features in either the wavefront aberrometery, and/or corneal topography maps. This can be achieved by first fitting the surface (either wavefront or topography) to smooth functions such as Zernike or Taylor polynomials, and then subtracting this smooth surface from the original surface data. The resulting map is the residual of what does not fit a smooth surface and is highly correlated with the tear film (Haixia Liu, Larry Thibos, Carolyn G. Begley, Arthur Bradley, “MEASUREMENT OF THE TIME COURSE OF OPTICAL QUALITY AND VISUAL DETERIORATION DURING TEAR BREAK-UP,” Investigative Ophthalmology & Visual Science, June 2010, Vol. 51, No. 6). A determination of whether the tear film is broken (if not smooth); an assessment of the tear film, including tear film breakup, can also be obtained by reviewing the shape of spots on the topographer. For instance, a finding or indication that the tear film is disrupted, or broken, may be based upon the shape of a spot in that, if the spots are not round, and have, for instance, an oblong or broken up shape, it indicates that tear film is disrupted. The existence of such a disrupted tear film may indicate that K value, and other ocular measurements may not be reliable. Further indications of the state of the tear film may be made by comparing the OCT and the topographer or wavefront data (Kob-Simultaneous Measurement of Tear Film Dynamics IOVS, July 2010, Vol. 51, No. 7).
In operation, as shown in
Following the collimating optical fiber 196, the OCT beam 214 continues through a z-scan device 193, 194. Preferably, the z-scan device is a Z telescope 193, which is operable to scan focus position of the laser pulse beam 66 in the patient's eye 101 along the Z axis. For example, the Z-telescope can include a Galilean telescope with two lens groups (each lens group includes one or more lenses). One of the lens groups moves along the Z axis about the collimation position of the Z-telescope 193. In this way, the focus position in the patient's eye 101 moves along the Z axis. In general, there is a relationship between the motion of lens group and the motion of the focus point. The exact relationship between the motion of the lens and the motion of the focus in the z axis of the eye coordinate system does not have to be a fixed linear relationship. The motion can be nonlinear and directed via a model or a calibration from measurement or a combination of both. Alternatively, the other lens group can be moved along the Z axis to adjust the position of the focus point along the Z axis. The Z-telescope 84 functions as a z-scan device for changing the focus point of the OCT beam 214 in the patient's eye 101.
The Z-scan device can be controlled automatically and dynamically by the controller 60 and selected to be independent or to interplay with the X and Y scan devices described next.
After passing through the z-scan device, the OCT beam 214 is incident upon an X-scan device 195, which is operable to scan the OCT beam 214 in the X direction, which is dominantly transverse to the Z axis and transverse to the direction of propagation of the OCT beam 214. The X-scan device 195 is controlled by the controller 60, and can include suitable components, such as a lens coupled to a MEMS device, a motor, galvanometer, or any other well-known optic moving device. The relationship of the motion of the beam as a function of the motion of the X actuator does not have to be fixed or linear. Modeling or calibrated measurement of the relationship or a combination of both can be determined and used to direct the location of the beam.
After being directed by the X-scan device 196, the OCT beam 214 is incident upon a Y scan device 197, which is operable to scan the OCT beam 214 in the Y direction, which is dominantly transverse to the X and Z axes. The Y-scan device 197 is controlled by the controller 60, and can include suitable components, such as a lens coupled to a MEMS device, motor, galvanometer, or any other well-known optic moving device. The relationship of the motion of the beam as a function of the motion of the Y actuator does not have to be fixed or linear. Modeling or calibrated measurement of the relationship or a combination of both can be determined and used to direct the location of the beam. Alternatively, the functionality of the X-Scan device 195 and the Y-Scan device 197 can be provided by an XY-scan device configured to scan the laser pulse beam 66 in two dimensions transverse to the Z axis and the propagation direction of the laser pulse beam 66. The X-scan and Y scan devices 195, 197 change the resulting direction of the OCT beam 214, causing lateral displacements of OCT beam 214 located in the patient's eye 101.
The OCT sample beam 214 is then directed to beam splitter 173 through lens 175 through quarter wave plate 171 and aperture 114 and to the patient eye 101. Reflections and scatter off of structures within the eye provide return beams that retrace back through the patient interface quarter wave plate 171, lens 175, beam splitter 173, y-scan device 197, x-scan device 195, z-scan device 193, optical fiber 196 and beam combiner 204 (
The quarter wave plate 171 described above has the effect that light returning into the instrument will have its polarization rotated by ninety degrees relative to the outgoing polarization. This can result in a situation that the OCT reference beam and signal light incident on the detector 220 will have nearly orthogonal polarizations so that the interference signal generated is extremely weak. One effective method to maximize the signal strength is to set the relevant OCT reference and sample light beams to be linearly polarized with, for example, a polarizing controller in both the sample arm and the reference arm. In one such embodiment, a first set 198 of polarization controllers (
The quarter wave plate 171 may be zero order design at either the OCT wavelength, the wavefront sensor wavelength, or an intermediate wavelength. Practical zero order wave plates made of crossed crystalline quartz plates are low cost and will behave as nearly as ideal over the wavelength range of interests, for instance if the center wavefront sensor wavelength is 840 nm and the center OCT wavelength is 1060 nm. Other alternatives are polymer waveplates or the more expensive achromatic quarter wave plates.
The optical measurement systems according to the present invention preferably comprise an iris imaging subsystem 40. The imaging subsystem 40 generally comprises an infrared light source, preferably infrared light source 152, and detector 141. In operation light from the light source 152 is directed along second optical path 160 to first optical path 170 and is subsequently directed to eye 101 as described above. Light reflected from the iris of eye 101 is reflected back along first optical path 170 to detector 141. In normal use, an operator will adjust a position or alignment of system 100 in XY and Z directions to align the patient according to the image detector array 141. In one embodiment of the iris imaging subsystem, eye 101 is illuminated with infrared light from light source 152. In this way, the wavefront obtained by wavefront sensor 155 will be registered to the image from detector array 141.
The image that the operator sees is the iris of eye 100. The cornea generally magnifies and slightly displaces the image from the physical location of the iris. So the alignment that is done is actually to the entrance pupil of the eye. This is generally the desired condition for wavefront sensing and iris registration.
Iris images obtained by the iris imaging subsystem may be used for registering and/or fusing the multiple data sets obtained by the various subsystems of the present invention, by methods described for instance in “Method for registering multiple data sets,” U.S. patent application Ser. No. 12/418,841, which is incorporated herein by reference. As set forth in U.S. patent application Ser. No. 12/418,841, wavefront aberrometry may be fused with corneal topography, optical coherence tomography and wavefront, optical coherence tomography and topography, pachymetry and wavefront, etc. For instance, with image recognition techniques it is possible to find the position and extent of various features in an image. Regarding iris registration images, features that are available include the position, size and shape of the pupil, the position, size and shape of the outer iris boundary (OIB), salient iris features (landmarks) and other features as are determined to be needed. Using these techniques, patient eye movement in between measurements as well as that during a measurement sequence can be identified. Further, changes in the eye itself (including those induced by the measurement, such as changes in the size of the pupil, changes in pupil location, etc.) can be identified.
In certain embodiments, an optical measurement system according the present includes a target fixation subsystem, and an assembly 100 shown in
In operation, light originates from the light source 152 or, alternatively, from video target backlight 182 and lens 186. Lens 185 collects the light and forms an aerial image T2. This aerial image is the one that the patient views. The patient focus is maintained on aerial image 182 during measurement so as to maintain the eye in a fixed focal position.
The operating sequence the optical measurement system and methods of the present is not particularly limited. A scan of the patient's eye may comprise one or more of a wavefront aberrometry measurement of a patient's eye utilizing the wavefront aberrometry subsystem, a corneal topography measurement of a patient's eye and an OCT scan of the patient's eye using the OCT subsystem, wherein the OCT scan includes a scan at each or one or more locations within the eye of the patient. These locations of the OCT scan may correspond to the location of the cornea, the location of the anterior portion of the lens, the location of the posterior portion of the lens and the location of the retina. In a preferred embodiment, the operating sequence includes each of a wavefront aberrometry measurement, a corneal topography measurement and an OCT scan, wherein the OCT scan is taken at least at the retina, the cornea and one of anterior portion of the patient's lens. Preferably, an iris image is taken simultaneously with or sequentially with an each of measurements taken with wavefront aberrometry subsystem the corneal topography subsystem and the OCT subsystem, including an iris image take simultaneously with or sequentially with the location of each OCT scan. This results in improved accuracy in the 3-dimensional modeling of the patient's eye by permitting the various data sets to be fused and merged into a 3-dimensional model.
Using the wavefront map obtained above from the wavefront aberrometer, the femtosecond laser system could be used to incise precise lenticules in corneas, and correct not only low order but also high order aberrations. The combination of these treatment methods is contemplated here.
Translation of Refractive Error Correction Treatment from Perturbation of Natural Free State of Eye to Applanated Docked Eye
In some example embodiments, an operator may use the wavefront aberrometer as described above to determine a patient's refractive error in their eye, sometimes including higher order aberrations. Corrections for the patient's refractive error may be determined including making plans to form a lenticule in the cornea, or to incise part of the cornea to correct for the determined refractive error. Iris registration may also take place using the wavefront aberrometer to help with identification and alignment of the laser system on a patient. But, such determinations of corrections and iris registration may be made with the wavefront aberrometer on a free eye, one that is in its natural state, not deformed or touched by any device or interface.
In some embodiments, during a laser treatment, a patient interface is used on the eye to be treated. Such interface may touch, dock or otherwise interact with the cornea of the patient's eye. In other words, the eye may be applanated by the patient interface for treatment. This may include compression of the eye and flattening of the cornea.
Embodiments of patient interfaces may include but are not limited to glass or plastic with a flat, curved, or liquid interface. If the patient interface touches and pushes on the eye, this applanation may distort and/or otherwise move the cornea from its natural curved shape into a flat shape or flatter shape to conform with the patient interface. Such applanation may also move, distort and/or otherwise stretch the iris of the eye as well. The iris distortion may result from a mechanical deformation by applanation of the patient interface and an apparent distortion due to the change of shape of the eye in the applanation.
Regarding iris registration, the system may use identified features of an iris as a guide to help line up the corrective incisions. Such systems and methods may use multiple features of the iris and use them as landmarks to compare the eye from its natural state to an applanated state. This is because pressing a spherically shaped cornea to a flat plane or flatter plane, may change the cornea-iris relational positions. By comparing multiple landmarks, the system can calibrate the movement of the landmarks before and after applanation to help determine a translation of the corrective incisions and determine the correct coordinates to incise the applanated eye.
Iris imaging may take place using white light illumination and/or infrared illumination. Each of these illuminations may have advantages and disadvantages, such as infrared illumination reducing iris constriction and white light illumination resulting in a sharper image, color images, and allowing a surgeon to visualize the iris in more natural conditions. For example, white light may refer to undivided broad spectrum of wavelengths of light with wavelengths from 400-700 nm and infrared light is higher than the visible spectrum, for example 850-1200 nm. In some examples, the white light may be generated using a combination of three sources of light, for example three light emitting diode (LED) lights, each with a different color of red, green, and blue. In some embodiments, a combination of both kinds of illumination, white and infrared, may be used.
Another consideration which may affect the treatment procedure is the orientation of the patient when the wavefront aberrometer is used to determine refractive error and obtain an iris image, and when the incision procedures are performed. In some embodiments, a patient is sitting or standing upright when the wavefront aberrometer is used, and laying down, supine, when the incision procedures are performed. When this orientation change occurs, the eyes of a patient twist slightly in their sockets, this is known as cyclotorsion rotation. In certain embodiments here, this cyclotorsion rotation may be accounted for in the translation of the cutting profile for any patient by adjusting the cutting points according to a previously measured cyclotorsion rotation or a standard cyclotorsion rotation amount.
This iris image translation can be coupled with translation of the refractive error correction determined from the wavefront aberrometer of the eye in its natural state to an applanated eye. The goal of the translation is to help ensure that when the eye returns to its natural state the incisions provide the intended corrections.
The compression of the cornea and eye may also be factored into the translation of the lenticule incisions. When making translation determinations, between how the corrective lenticule may be shaped in the free natural state eye, and the perturbed docked eye, some assumptions may be made. It may be assumed that the cornea conforms to patient interface during docking. It may also be assumed that the cornea in tissue volume does not change during docking. Using these assumptions, maps may be created of the eye based on the addition of a known perturbation to an eye. This addition may be a theoretically based disturbance to the location of the lenticule in the docked eye. It should be noted that empirical corrections of the calculation based on other perturbations or errors for correction may be added to the calculated values or used to modify the calculated values.
Below are calculations for translating points of a lenticule to be incised while it is in its natural free state and in an applanated state. In some embodiments, these relations describe the primary changes introduced by a flat surface or a curved surface of a patient interface applanation. The relationships may be used or the relationships may be further be developed by empirical experimental relations. Thus, the surgeon user may begin with the below information and build in other changes for customization for patient treatment.
Flat Patient Interface Examples
An ablation depth profile may be determined to remove the desired lenticule, even if the cornea is applanated. To remove a predetermined lenticule shape from a free cornea, we can transform the known shape into the cutting shape for eye under applanation by either a flat or a curved patient interfaces.
Where 1920 is Ra which is a Radius of curvature of anterior cornea. And 1922 is H which is a cut depth of lenticule central plane. And 1924 is R=Ra−H which is a Radius of curvature of the lenticular central plane, before applanation. And (ρ, φ) is a Location of interest before applanation with ρ as 1912. And 1928 is θ which is an Angle subtended by location of interest relative to Z-axis. And 1930 is Δ(ρ, φ) which is a Z-difference between lenticule surfaces at (ρ, φ) before applanation. And 1932 is (ρ′, φ) which is a location of interest under flat applanation. And Δ′(ρ′,φ) is a Z-difference between lenticule surfaces at (ρ′,φ) under flat applanation with ρ′ as 1914.
Thus the lenticule shape transform is given for a cornea under a flat patient interface, with sinc x sin(x)/x. The lenticule shape transform may be given by:
Δ′(ρ′,φ)=Δ(ρ,φ)·sinc(2θ), with ρ′=R·θ
Curved Patient Interface Examples
If a patient interface is not flat, but curved in any way, the translation calculations can be changed to accommodate for the curve. Below are theoretical calculations which may be used to determine the translation of points between a lenticule in a natural free state cornea, and one applanated by a curved interface.
Thus, the lenticule shape transform under curved patient interface is given by:
It should be noted that any kind of ultrashort laser may be used to treat the eye and incise the cornea. Examples of ultrashort lasers include but are not limited to picosecond, femtosecond, or nanosecond lasers. In some examples embodiments, the ultrashort pulsed laser has a pulse width between 10 fs and 5 ns. In some example embodiments, the ultrashort pulsed laser has a wavelength spectrum centered at between 320 nm and 1200 nm. In some example embodiments, the ultrashort pulsed laser has a pulse width between 80 fs and 250 fs. In some example embodiments, the ultrashort pulsed laser has a wavelength spectrum centered at, or has a center mass, between 1020 nm and 1070 nm and/or more specifically between 1025 nm and 1065 nm. Different embodiments may also include lasers with different profiles such as a Beckman peak or single peak.
These systems and methods could be used to treat any kind of refractive error such as myopia with or without astigmatism, hyperopia with or without astigmatism, and mixed astigmatism. Any kind of cutting profiles can be incised using these systems and methods including but not limited to lenticules, PRK removal of corneal layers, or other shapes. Transition profiles may be incised as well such as extending the top and bottom of a lenticule to aid in removal of the lenticule. Other transition profiles may include an internal side cut. In some examples, the side incision has an arc length between 1 mm and 10 mm.
In some examples, an apex of the lenticule and an apex of the cornea may be between 60 μm and 200 μm. In some examples, the lenticule has a lateral diameter between 4 mm and 8 mm.
All patents and patent applications cited herein are hereby incorporated by reference in their entirety.
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 terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments and does not pose a limitation on the scope of the embodiments 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.
While certain illustrated embodiments of this disclosure have been shown and described in an exemplary form with a certain degree of particularity, those skilled in the art will understand that the embodiments are provided by way of example only, and that various variations can be made without departing from the spirit or scope of the embodiments. Thus, it is intended that this disclosure cover all modifications, alternative constructions, changes, substitutions, variations, as well as the combinations and arrangements of parts, structures, and steps that come within the spirit and scope of the embodiments as generally expressed by the following claims and their equivalents.
As disclosed herein, features consistent with the present invention may be implemented via computer-hardware, software and/or firmware. For example, the systems and methods disclosed herein may be embodied in various forms including, for example, a data processor, such as a computer that also includes a database, digital electronic circuitry, firmware, software, computer networks, services, or in combinations of them. Further, while some of the disclosed implementations describe specific hardware components, systems and methods consistent with the innovations herein may be implemented with any combination of hardware, software and/or firmware. Moreover, the above-noted features and other aspects and principles of the innovations herein may be implemented in various environments. Such environments and related applications may be specially constructed for performing the various routines, processes and/or operations according to the invention or they may include a general-purpose computer or computing platform selectively activated or reconfigured by code to provide the necessary functionality. The processes disclosed herein are not inherently related to any particular computer, network, architecture, environment, or other apparatus, and may be implemented by a suitable combination of hardware, software, and/or firmware. For example, various general-purpose machines may be used with programs written in accordance with teachings of the invention, or it may be more convenient to construct a specialized apparatus or system to perform the required methods and techniques.
Aspects of the method and system described herein, such as the logic, may be implemented as functionality programmed into any of a variety of circuitry, including programmable logic devices (“PLDs”), such as field programmable gate arrays (“FPGAs”), programmable array logic (“PAL”) devices, electrically programmable logic and memory devices and standard cell-based devices, as well as application specific integrated circuits. Some other possibilities for implementing aspects include: memory devices, microcontrollers with memory (such as 1PROM), embedded microprocessors, firmware, software, etc. Furthermore, aspects may be embodied in microprocessors having software-based circuit emulation, discrete logic (sequential and combinatorial), custom devices, fuzzy (neural) logic, quantum devices, and hybrids of any of the above device types. The underlying device technologies may be provided in a variety of component types, e.g., metal-oxide semiconductor field-effect transistor (“MOSFET”) technologies like complementary metal-oxide semiconductor (“CMOS”), bipolar technologies like emitter-coupled logic (“ECL”), polymer technologies (e.g., silicon-conjugated polymer and metal-conjugated polymer-metal structures), mixed analog and digital, and so on.
It should also be noted that the various logic and/or functions disclosed herein may be enabled using any number of combinations of hardware, firmware, and/or as data and/or instructions embodied in various machine-readable or computer-readable media, in terms of their behavioral, register transfer, logic component, and/or other characteristics. Computer-readable media in which such formatted data and/or instructions may be embodied include, but are not limited to, non-volatile storage media in various forms (e.g., optical, magnetic or semiconductor storage media) and carrier waves that may be used to transfer such formatted data and/or instructions through wireless, optical, or wired signaling media or any combination thereof. Examples of transfers of such formatted data and/or instructions by carrier waves include, but are not limited to, transfers (uploads, downloads, e-mail, etc.) over the Internet and/or other computer networks via one or more data transfer protocols (e.g., HTTP, FTP, SMTP, and so on).
Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of “including, but not limited to.” Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words “herein,” “hereunder,” “above,” “below,” and words of similar import refer to this application as a whole and not to any particular portions of this application. When the word “or” is used in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list.
Although certain presently preferred implementations of the invention have been specifically described herein, it will be apparent to those skilled in the art to which the invention pertains that variations and modifications of the various implementations shown and described herein may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention be limited only to the extent required by the applicable rules of law.
The foregoing description, for purpose of explanation, has been described with reference to specific examples. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The examples were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various examples with various modifications as are suited to the particular use contemplated.
This application claims priority to, and the benefit of, under 35 U.S.C. §119(e) of U.S. Provisional Appl. No. 62/359,634, filed Jul. 7, 2016, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62359634 | Jul 2016 | US |
