Patent Description:
For example, in the well-known procedure known as LASIK (laser-assisted in situ keratomileusis), a laser eye surgery system employing ultraviolet radiation is used for ablating and reshaping the anterior surface of the cornea to correct a refractive condition, such as myopia or hyperopia. Further, prior to ablation during LASIK, the cornea is incised with a laser eye surgery system employing a non-ultraviolet, ultra-short pulsed laser beam to create a flap to expose an underlying portion of the cornea so that it can be then be ablated and reshaped with ultraviolet laser beams. Afterwards, the treated portion is covered with the flap.

More recently, laser eye surgery systems have been developed for cataract procedures. These systems can be used for various surgical procedures, including for instance: (<NUM>) creating one or more incisions in the cornea or in the limbus to reshape the cornea, (<NUM>) creating one or more incisions in the cornea to provide access for a cataract surgery instrument and/or to provide access for implantation of an intraocular lens, (<NUM>) incising the anterior lens capsule (anterior capsulotomy) to provide access for removing a cataractous lens, (<NUM>) segmenting and/or fragmenting a cataractous lens, and/or (<NUM>) incising the posterior lens capsule (posterior capsulotomy) for various cataract-related procedures.

With capsulotomy, the surgeon creates a circular opening in the lens capsule, which is a cellophane-like bag that holds the lens. The incision to create this circular opening is one of the most critical steps of the cataract procedure as its size, shape, and centering may impact the effective positioning of an artificial intraocular lens (IOL) following removal of the cataractous lens. If the artificial lens becomes de-centered or shifts back or forward by even a slight degree, its performance may be diminished leading to refractive error. Laser eye surgery systems for cataract procedures therefore often include imaging systems for more accurate and precise placement of incisions and capsulotomy.

Sometimes, however, to reduce the possibilities of incomplete cutting, a capsulotomy may take longer to perform than is ideal, especially when the scan patterns are substantially longer in a depth dimension than the capsule. Further, slight eye movement and/or lens capsule movement may increase the possibility of an inadequate capsule incision. Hence, laser surgery systems with improved characteristics for intraocular target identification and incision, and related methods, would be beneficial.

<CIT> discloses a device for processing material of a workpiece, comprising an imaging unit to detect structures within the workpiece using electromagnetic radiation wherein the electromagnetic radiation of the imaging unit is radiated via the beam-deflection unit and the focusing lens into the workpiece, and evaluating device is provided and compares the position of the focus of the laser radiation determined by the detector unit with the expected position of the focus in the image of the workpiece obtained by the imaging unit. Further, <CIT> describes a system comprising control electronics, a light source, an attenuator, a beam expander, focusing lens and reflection means, wherein an aperture pinhole is placed in the focal spot of a formed beam as a conjugate of the laser beam focus in a target structure.

Accordingly, this disclosure provides imaging and/or treatment systems and related methods that can be used in suitable laser surgery systems such as, for example, laser eye surgery systems, that substantially obviate one or more problems due to limitations and disadvantages of the related art. In the special case of a laser-created capsulotomy, the actual target depth requirements is minimal as the anterior lens capsule in humans is only about <NUM> micro meters thick while the posterior lens capsule is only <NUM> micro meters thick. The optics used in conventional cataract laser systems have a depth of field of single laser pulses of about <NUM> micrometers down to <NUM> micrometers. As such, in principal and in an ideal case, one would only require one single pass of the laser to cut the lens capsule as the material is much thinner than the depth effect of the laser systems. Tissue movements and especially limited alignment and calibration tolerances of the laser systems, however, require that the laser actively cuts several hundreds of micrometers in depth to ensure achieving a complete cut. In some situations, it may be advantageous to treat intraocular targets with a limited number of scans of a treatment laser focal point. This may reduce inadvertent eye/intraocular target movement during or between scans and may reduce the amount of energy delivered to a patient's eye. For example, it may be preferable to provide a capsulotomy with <NUM> or fewer, <NUM> or fewer, <NUM> or fewer, <NUM> or fewer, and in some cases <NUM>, <NUM>, or fewer scans of a treatment beam. Thus, some methods may adjust a focal point location as the focal point is scanned across the capsule surface. In some situations, the focal point depth may be adjusted after each pulse. In other situations, the focal point depth may be adjusted after a plurality of pulses. Since the focal point of the treatment laser may be continually adjusted to be positioned on an intraocular target, fewer scans may be required to modify and/or treat the target.

In some embodiments of the present disclosure methods of modifying an intraocular target are provided. For instance, the intraocular target may be the lens capsule where the capsule is modified by incising the tissue with a treatment beam. The methods may include the step of focusing a treatment beam to a focal point at a first location in the eye, and measuring an intensity signal of electromagnetic radiation reflected from the first location in response to the treatment beam. A second location of the focal point may be identified in the eye using the measured intensity signal of the electromagnetic radiation reflected from the first location. The focal point of the treatment beam may then be scanned toward the second location where tissue at the second location can be altered.

In some embodiments, the method may include a step of scanning a focal point of an imaging beam within the eye and measuring an intensity signal of electromagnetic radiation reflected from focal point locations in response to the imaging beam so as to locate the intraocular target, e.g., the lens capsule of the eye. Thereafter, the treatment beam may be aligned with the located lens capsule. Optionally, the method may include generating the treatment beam and the imaging beam using the same electromagnetic radiation beam source.

In some embodiments, the intensity signal may be measured by a confocal detector. Further, the focal point of the treatment beam may be scanned to a plurality of different locations in the eye. In some embodiments, a depth of the focal point of the treatment beam is dithered. In some embodiments, the focal point may be scanned from a posterior depth toward an anterior depth. Moreover, the focal point of the treatment beam may be scanned in the xy-direction transverse to a direction of beam propagation.

Optionally, the second location may be identified based in part on phase information of the intensity signal. In some embodiments, the second location may be identified by comparing the measured intensity signal to an upper threshold value and a lower threshold value. The identified second location may have a depth less than the depth of the first location when the measured intensity signal of the electromagnetic radiation reflected from the first location is above the upper threshold value. The identified second location may have a depth greater than the depth of the first location where the measured intensity signal of the electromagnetic radiation reflected from the first location is below the lower threshold value. Further, in some embodiments, the identified second location has a depth equal to the depth of the first location when the measured intensity signal of the electromagnetic radiation reflected from the first location is greater than the lower threshold value and less than the upper threshold value.

In some aspects of the disclosure, a non-transitory computer-readable storage medium including a set of computer executable instructions for modifying an intraocular target of the eye is provided. Execution of the instructions by a computer processor may cause the processor to carry out one or more of the steps described above. In some embodiments, a second location of the focal point may be determined by using a feedback loop based in part on the received intensity signal of the electromagnetic radiation reflected from the focal point at the first location.

In certain aspects of the disclosure, systems for modifying an intraocular target of the eye are provided. The systems may include an electromagnetic beam source configured to generate a treatment beam and/or an imaging beam. Additionally, the system may include optics configured to focus the treatment beam and/or the imaging beam to a focal point and scan the focal point to locations in the eye. A detector may be configured to receive electromagnetic radiation reflected from the focal point of the treatment beam and to measure an intensity signal of reflected electromagnetic radiation. Furthermore, a controller may be coupled with the beam scanner and the detector and configured to identify a subsequent location of the focal point of the treatment beam using a feedback loop based in part on the measured intensity signal of the electromagnetic radiation reflected from the focal point.

Optionally, the detector may be a confocal detector. In some embodiments, the controller can be configured to dither a depth of the focal point of the treatment beam. The controller may also scan the focal point of the treatment beam from a posterior depth toward an anterior depth so as to avoid beam travel through modified tissue. In some embodiments, the feedback loop may be based in part on phase information of the measured intensity signal.

In some embodiments, the controller may identify the subsequent location of the treatment beam focal point by comparing the measured intensity signal with an upper threshold value with that of a lower threshold value. The identified subsequent location may have a depth less than a depth of the initial focal point location when the measured intensity signal of the electromagnetic radiation reflected from the focal point location is above the upper threshold value. The identified subsequent location may have a depth greater than the depth of the initial focal point location when the measured intensity signal of the electromagnetic radiation reflected from the focal point location is below the lower threshold value. In some embodiments, the system controller may maintain the depth of the treatment beam focal point when the measured intensity signal of the electromagnetic radiation reflected from the focal point is greater than the lower threshold value and less than the upper threshold value.

This summary and the following 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, aspects, objects and advantages of embodiments of this invention are set forth in the descriptions, drawings, and the claims, and in part, will be apparent from the drawings and detailed description, or may be learned by practice.

Systems for imaging and/or treating a patient's eye are provided. In many embodiments, a free-floating mechanism provides a variable optical path by which a portion of an electromagnetic beam reflected from a focal point disposed within the eye is directed to a path length insensitive imaging assembly such as a confocal detection assembly. In many embodiments, the free-floating mechanism is configured to accommodate patient eye movement while maintaining alignment between an electromagnetic radiation beam and the eye. The electromagnetic radiation beam can be configured for: (<NUM>) imaging the eye; (<NUM>) treating the eye; and/or (<NUM>) imaging as well as treating the eye.

Referring now to the drawings in which like numbers reference similar elements, <FIG> schematically illustrates a laser surgery system <NUM>, according to many embodiments. The laser surgery system <NUM> may include a laser assembly <NUM>, a confocal detection assembly <NUM>, a free- floating mechanism <NUM>, a scanning assembly <NUM>, an objective lens assembly <NUM>, and a patient interface device <NUM>. The patient interface device <NUM> may be configured to interface with a patient <NUM>. The patient interface device <NUM> may be supported by the objective lens assembly <NUM>, which may be supported by the scanning assembly <NUM>. The scanning assembly <NUM> may in turn be supported by the free-floating mechanism <NUM>. A portion of the free-floating mechanism <NUM> may have a fixed position and orientation relative to the laser assembly <NUM> and the confocal detection assembly <NUM>.

In some embodiments, the patient interface device <NUM> may be configured to interface with an eye of the patient <NUM>. For example, the patient interface device <NUM> can be configured to be coupled via vacuum suction to an eye of the patient <NUM> as described in co-pending <CIT>, the entire disclosure of which is hereby incorporated by reference. The laser surgery system <NUM> can further optionally include a base assembly <NUM> that can be fixed in place or be repositionable. For example, the base assembly <NUM> can be supported by a support linkage that is configured to allow selective repositioning of the base assembly <NUM> relative to a patient and to secure the base assembly <NUM> in a selected fixed position relative to the patient. Such a support linkage can be supported in any suitable manner such as, for example, by a fixed support base or by a movable cart that can be repositioned to a suitable location adjacent to a patient. In many embodiments, the support linkage includes setup joints with each setup joint being configured to permit selective articulation of the setup joint, and can be selectively locked to prevent inadvertent articulation of the setup joint, thereby securing the base assembly <NUM> in a selected fixed position relative to the patient when the setup joints are locked.

In many embodiments, the laser assembly <NUM> may be configured to emit an electromagnetic radiation beam <NUM>. The beam <NUM> can include a series of laser pulses of any suitable energy level, duration, and repetition rate.

In many embodiments, the laser assembly <NUM> incorporates femtosecond (FS) laser technology. By using femtosecond laser technology, a short duration (e.g., approximately <NUM>-<NUM> seconds in duration) laser pulse (with energy level in the micro joule range) can be delivered to a tightly focused point to disrupt tissue, thereby substantially lowering the energy level required to image and/or modify an intraocular target as compared to laser pulses having longer durations.

The laser assembly <NUM> can produce laser pulses having a wavelength suitable to treat and/or to image tissue. For example, the laser assembly <NUM> can be configured to emit an electromagnetic radiation beam <NUM> such as that emitted by any of the laser surgery systems described in co-pending <CIT>; and <CIT>, the full disclosures of which are incorporated herein by reference. For example, the laser assembly <NUM> can produce laser pulses having a wavelength in the range of <NUM> to <NUM>. For example, the laser assembly <NUM> can have a diode-pumped solid-state configuration with a <NUM> (+/-<NUM>) nm center wavelength. As another example, the laser assembly <NUM> can produce laser pulses having a wavelength in the range of <NUM> to <NUM>. For example, the laser assembly <NUM> can include an Nd:YAG laser source operating at the 3rd harmonic wavelength (<NUM>) and producing pulses having <NUM> picosecond to <NUM> nanosecond pulse duration. Depending on the spot size, typical pulse energies used can be in the nano joule to micro joule range. The laser assembly <NUM> can also include two or more lasers of any suitable configuration.

The laser assembly <NUM> can include control and conditioning components. For example, such control components can include components such as a beam attenuator to control the energy of the laser pulse and the average power of the pulse train, a fixed aperture to control the cross-sectional spatial extent of the beam containing the laser pulses, one or more power monitors to monitor the flux and repetition rate of the beam train and therefore the energy of the laser pulses, and a shutter to allow/block transmission of the laser pulses. Such conditioning components can include an adjustable zoom assembly and a fixed optical relay to transfer the laser pulses over a distance while accommodating laser pulse beam positional and/or directional variability, thereby providing increased tolerance for component variation.

In many embodiments, the laser assembly <NUM> and the confocal detection assembly <NUM> may have fixed positions relative to the base assembly <NUM>. The beam <NUM> emitted by the laser assembly <NUM> may propagate along a fixed optical path through the confocal detection assembly <NUM> to the free-floating mechanism <NUM>. The beam <NUM> may propagate through the free-floating mechanism <NUM> along a variable optical path <NUM>, which may deliver the beam <NUM> to the scanning assembly <NUM>. In many embodiments, the beam <NUM> emitted by the laser assembly <NUM> may be collimated so that the beam <NUM> is not impacted by patient-movement-induced changes in the length of the optical path between the laser assembly <NUM> and the scanner <NUM>. The scanning assembly <NUM> may be operable to scan the beam <NUM> (e.g., via controlled variable deflection of the beam <NUM>) in at least one dimension. In many embodiments, the scanning assembly <NUM> is operable to scan the beam <NUM> in two dimensions transverse to the direction of propagation of the beam <NUM> and may be further operable to scan the location of a focal point of the beam <NUM> in the direction of propagation of the beam <NUM>. The scanned beam may be emitted from the scanning assembly <NUM> to propagate through the objective lens assembly <NUM>, through the interface device <NUM>, and to the patient <NUM>.

The free-floating mechanism <NUM> may be configured to accommodate a range of movement of the patient <NUM> relative to the laser assembly <NUM> and the confocal detection assembly <NUM> in one or more directions while maintaining alignment of the beam <NUM> emitted by the scanning assembly <NUM> with the patient <NUM>. For example, in many embodiments, the free-floating mechanism <NUM> may be configured to accommodate a range movement of the patient <NUM> in any direction defined by any combination of unit orthogonal directions (X, Y, and Z).

The free-floating mechanism <NUM> may support the scanning assembly <NUM> and may provide the variable optical path <NUM>, which may change in response to movement of the patient <NUM>. Because the patient interface device <NUM> may be interfaced with the patient <NUM>, movement of the patient <NUM> may result in corresponding movement of the patient interface device <NUM>, the objective lens assembly <NUM>, and the scanning assembly <NUM>. The free-floating mechanism <NUM> can include, for example, any suitable combination of a linkage that accommodates relative movement between the scanning assembly <NUM> and, for example, the confocal detection assembly <NUM>, and optical components suitably tied to the linkage so as to form the variable optical path <NUM>. Optionally, the free-floating mechanism <NUM> can be configured as described in <CIT>, entitled "Laser Surgery System," the entire disclosure of which is incorporated herein by reference.

A portion of the electromagnetic radiation beam <NUM> may reflect from an eye tissue at the focal point and may propagate back to the confocal detection assembly <NUM>. Specifically, a reflected portion of the electromagnetic radiation beam <NUM> may travel back through the patient interface device <NUM>, back through the objective lens assembly <NUM>, back through (and de-scanned by) the scanning assembly <NUM>, back through the free-floating mechanism <NUM> (along the variable optical path <NUM>), and to the confocal detection assembly <NUM>. In many embodiments, the reflected portion of the electromagnetic radiation beam that travels back to the confocal detection assembly <NUM> may be directed to be incident upon a sensor that generates an intensity signal indicative of intensity of the incident portion of the electromagnetic radiation beam. The intensity signal, coupled with associated scanning of the focal point within the eye, can be processed in conjunction with the parameters of the scanning to, for example, image/locate structures of the eye, such as the anterior surface of the cornea, the posterior surface of the cornea, the iris, the anterior surface of the lens capsule, and the posterior surface of the lens capsule. In many embodiments, the amount of the reflected electromagnetic radiation beam that travels to the confocal detection assembly <NUM> may be substantially independent of expected variations in the length of the variable optical path <NUM> due to patient movement, thereby enabling the ability to ignore patient movements when processing the intensity signal to image/locate structures of the eye.

<FIG> schematically illustrates details of an embodiment of the laser surgery system <NUM>. Specifically, example configurations are schematically illustrated for the laser assembly <NUM>, the confocal detection assembly <NUM>, and the scanning assembly <NUM>. As shown in the illustrated embodiment, the laser assembly <NUM> can include an ultrafast (UF) laser <NUM> (e.g., a femtosecond laser), alignment mirrors <NUM>, <NUM>, a beam expander <NUM>, a one-half wave plate <NUM>, a polarizer and beam dump device <NUM>, output pickoffs and monitors <NUM>, and a system-controlled shutter <NUM>. The electromagnetic radiation beam <NUM> output by the laser <NUM> may be deflected by the alignment mirrors <NUM>, <NUM>. In many embodiments, the alignment mirrors <NUM>, <NUM> may be adjustable in position and/or orientation so as to provide the ability to align the beam <NUM> with the downstream optical path through the downstream optical components. Next, the beam <NUM> may pass through the beam expander <NUM>, which can increase the diameter of the beam <NUM>. Next, the expanded beam <NUM> may pass through the one-half wave plate <NUM> before passing through the polarizer. The beam exiting the laser may be linearly polarized. The one-half wave plate <NUM> can rotate this polarization. The amount of light passing through the polarizer depends on the angle of the rotation of the linear polarization. Therefore, the one-half wave plate <NUM> with the polarizer may act as an attenuator of the beam <NUM>. The light rejected from this attenuation may be directed into the beam dump. Next, the attenuated beam <NUM> may pass through the output pickoffs and monitors <NUM> and then through the system-controlled shutter <NUM>. By locating the system-controlled shutter <NUM> downstream of the output pickoffs and monitors <NUM>, the power of the beam <NUM> can be checked before opening the system-controlled shutter <NUM>.

As shown in the illustrated embodiment, the confocal detection assembly <NUM> can include a polarization-sensitive device such as a polarized or an unpolarized beam splitter <NUM>, a filter <NUM>, a focusing lens <NUM>, a pinhole aperture <NUM>, and a detection sensor <NUM>. A one-quarter wave plate <NUM> may be disposed downstream of the polarized beam splitter <NUM>. The beam <NUM> as received from the laser assembly <NUM> may be polarized so as to pass through the polarized beam splitter <NUM>. Next, the beam <NUM> may pass through the one-quarter wave plate <NUM>, thereby rotating the polarization axis of the beam <NUM>. A quarter rotation may be a preferred rotation amount. After reflecting from a focal point in the eye, a returning reflected portion of the beam <NUM> may pass back through the one-quarter wave plate <NUM>, thereby further rotating the polarization axis of the returning reflected portion of the beam <NUM>. After passing back through the one-quarter wave plate <NUM>, the returning reflected portion of the beam may experience a total polarization rotation of <NUM> degrees so that the reflected light from the eye may be fully reflected by the polarized beam splitter <NUM>. A birefringence of the cornea can also be taken into account if, for example, the imaged structure is the lens. In such a case, the plate <NUM> can be adjusted/configured so that the double pass of the plate <NUM> as well as the double pass of the cornea sum up to a polarization rotation of <NUM> degrees. Because the birefringence of the cornea may be different form patient to patient, the configuration/adjustment of the plate <NUM> can be done dynamically so as to optimize the signal returning to the detection sensor <NUM>. In some embodiments, the plate <NUM> may be rotated an angle. Accordingly, the returning reflected portion of the beam <NUM> may be polarized to be at least partially reflected by the polarized beam splitter <NUM> so as to be directed through the filter <NUM>, through the lens <NUM>, and to the pinhole aperture <NUM>. The filter <NUM> can be configured to block wavelengths other than the wavelengths of interest. The pinhole aperture <NUM> may block any returning reflected portion of the beam <NUM> reflected from locations other than the focal point from reaching the detection sensor <NUM>. Because the amount of returning reflected portion of the beam <NUM> that reaches the detection sensor <NUM> depends upon the nature of the tissue at the focal point of the beam <NUM>, the signal generated by the detection sensor <NUM> can be processed in combination with data regarding the associated locations of the focal point so as to generate image/location data for structures of the eye.

As shown in the illustrated embodiment, the scanning assembly <NUM> can include a z-scan device <NUM> and a xy-scan device <NUM>. The z-scan device <NUM> may be operable to vary a convergence/divergence angle of the beam <NUM> and thereby change a location of the focal point in the direction of propagation of the beam <NUM>. For example, the z-scan device <NUM> can include one or more lenses that are controllably movable in the direction of propagation of the beam <NUM> to vary a convergence/divergence angle of the beam <NUM>. The xy-scan device <NUM> may be operable to deflect the beam <NUM> in two dimensions transverse to the direction of propagation of the beam <NUM>. For example, the xy-scan device <NUM> can include one or more mirrors that are controllably deflectable to scan the beam <NUM> in two dimensions transverse to the direction of propagation of the beam <NUM>. Accordingly, the combination of the z-scan device <NUM> and the xy-scan device <NUM> can be operated to controllably scan the focal point in three dimensions, for example, within the eye of the patient.

As shown in the illustrated embodiment, a camera <NUM> and associated video illumination <NUM> can be integrated with the scanning assembly <NUM>. The camera <NUM> and the beam <NUM> may share a common optical path through the objective lens assembly <NUM> to the eye. A video dichroic <NUM> may be used to combine/separate the beam <NUM> with/from the illumination wavelengths used by the camera. For example, the beam <NUM> can have a wavelength of about <NUM> and the video illumination <NUM> can be configured to emit illumination having wavelengths greater than <NUM>. Accordingly, the video dichroic <NUM> can be configured to reflect the <NUM> wavelength while transmitting wavelengths greater than <NUM>.

<FIG> is a simplified block diagram of acts of a method <NUM>, according tomany embodiments, of imaging an eye. Any suitable device, assembly, and/or system, such as described herein, can be used to practice the method <NUM>. The method <NUM> may include using a beam source to generate an electromagnetic radiation beam (act <NUM>).

The method <NUM> may include propagating the electromagnetic radiation beam from a beam source to a scanner along a variable optical path having an optical path length that changes in response to movement of the eye (act <NUM>). The method <NUM> may include focusing the electromagnetic radiation beam to a focal point at a location within the eye (act <NUM>). The method <NUM> may include using the scanner to scan the focal point to different locations within the eye (act <NUM>). The method <NUM> may include propagating a portion of the electromagnetic radiation beam reflected from the focal point location back along the variable optical path to a sensor (act <NUM>). The method <NUM> may include using the sensor to generate an intensity signal indicative of the intensity of a portion of the electromagnetic radiation beam reflected from the focal point location and propagated to the sensor (act <NUM>).

<FIG>, <FIG> are simplified block diagrams of optional steps or acts that can be accomplished as part of the method <NUM>. For example, the method <NUM> can include using a first support assembly to support the scanner so as to accommodate relative movement between the scanner and the first support assembly so as to accommodate movement of the eye (act <NUM>). The method <NUM> can include using a second support assembly to support the first support assembly so as to accommodate relative movement between the first support assembly and the second support assembly so as to accommodate movement of the eye (act <NUM>). The method <NUM> can include using the first support assembly to support a first reflector configured to reflect the electromagnetic radiation beam so as to propagate to the scanner along a portion of the variable optical path (act <NUM>). The method <NUM> can include using a base assembly to support the second support assembly so as to accommodate relative movement between the second support assembly and the base assembly so as to accommodate movement of the eye (act <NUM>). The method <NUM> can include using the second support assembly to support a second reflector configured to reflect the electromagnetic radiation beam to propagate along a portion of the variable optical path so as to be incident on the first reflector (act <NUM>). The method <NUM> can include using the sensor to generate the intensity signal comprises passing a reflected portion of the electromagnetic radiation beam through an aperture to block portions of the electromagnetic radiation beam reflected from locations other than the focal point location (act <NUM>). The method <NUM> can include passing the electromagnetic radiation beam through a polarization- sensitive device (act <NUM>). The method <NUM> can include modifying polarization of at least one of the electromagnetic radiation beam and a portion of the electromagnetic radiation beam reflected from the focal point location (act <NUM>). The method <NUM> can include using the polarization-sensitive device to reflect a portion of the electromagnetic radiation beam reflected from the focal point location so as to be incident upon the sensor (act <NUM>).

<FIG> schematically illustrates a laser surgery system <NUM> according to many embodiments. The laser surgery system <NUM> includes the laser assembly <NUM>, the confocal detection assembly <NUM>, the free-floating mechanism <NUM>, the scanning assembly <NUM>, the objective lens assembly <NUM>, the patient interface <NUM>, communication paths <NUM>, control electronics <NUM>, control panel/graphical user interface (GUI) <NUM>, and user interface devices <NUM>. The control electronics <NUM> includes processor <NUM>, which includes memory <NUM>. The patient interface <NUM> is configured to interface with a patient <NUM>. The control electronics <NUM> is operatively coupled via the communication paths <NUM> with the laser assembly <NUM>, the confocal detection assembly <NUM>, the free-floating mechanism <NUM>, the scanning assembly <NUM>, the control panel/GUI <NUM>, and the user interface devices <NUM>.

The scanning assembly <NUM> can include a z-scan device and a xy-scan device. The laser surgery system <NUM> can be configured to focus the electromagnetic radiation beam <NUM> to a focal point that is scanned in three dimensions. The z-scan device can be operable to vary the location of the focal point in the direction of propagation of the beam <NUM>. The xy-scan device can be operable to scan the location of the focal point in two dimensions transverse to the direction of propagation of the beam <NUM>. Accordingly, the combination of the z-scan device and the xy-scan device can be operated to controllably scan the focal point of the beam in three dimensions, including: within a tissue of the patient <NUM> such as within an eye tissue of the patient <NUM>. The scanning assembly <NUM> may be supported by the free-floating mechanism <NUM>, which may accommodate patient movement induced movement of the scanning assembly <NUM> relative to the laser assembly <NUM> and the confocal detection assembly <NUM> in three dimensions.

The patient interface <NUM> is coupled to the patient <NUM> such that the patient interface <NUM>, the objective lens assembly <NUM>, and the scanning assembly <NUM> move in conjunction with the patient <NUM>. For example, in many embodiments, the patient interface <NUM> employs a suction ring that is vacuum attached to an eye of the patient <NUM>. The suction ring can be coupled with the patient interface <NUM>, for example, using vacuum to secure the suction ring to the patient interface <NUM>.

The control electronics <NUM> controls the operation of and/or can receive input from the laser assembly <NUM>, the confocal detection assembly <NUM>, the free-floating assembly <NUM>, the scanning assembly <NUM>, the patient interface <NUM>, the control panel/GUI <NUM>, and the user interface devices <NUM> via the communication paths <NUM>. The communication paths <NUM> can be implemented in any suitable configuration, including any suitable shared or dedicated communication paths between the control electronics <NUM> and the respective system components.

The control electronics <NUM> can include any suitable components, such as one or more processor, one or more field-programmable gate array (FPGA), and one or more memory storage devices. In many embodiments, the control electronics <NUM> controls the control panel/GUI <NUM> to provide for pre-procedure planning according to user specified treatment parameters as well as to provide user control over the laser eye surgery procedure.

The control electronics <NUM> can include a processor/controller <NUM> that is used to perform calculations related to system operation and provide control signals to the various system elements. A computer readable medium <NUM> is coupled to the processor <NUM> in order to store data used by the processor and other system elements. The processor <NUM> interacts with the other components of the system as described more fully throughout the present specification. In an embodiment, the memory <NUM> can include a look up table that can be utilized to control one or more components of the laser system surgery system <NUM>.

The processor <NUM> can be a general purpose microprocessor configured to execute instructions and data, such as a Pentium processor manufactured by the Intel Corporation of Santa Clara, California. It can also be an Application Specific Integrated Circuit (ASIC) that embodies at least part of the instructions for performing the method according to the embodiments of the present disclosure in software, firmware and/or hardware. As an example, such processors include dedicated circuitry, ASICs, combinatorial logic, other programmable processors, any combinations thereof, and the like.

The memory <NUM> can be local or distributed as appropriate to the particular application. Memory <NUM> can include a number of memories including a main random access memory (RAM) for storage of instructions and data during program execution and a read only memory (ROM) in which fixed instructions are stored. Thus, the memory <NUM> provides persistent (non-volatile) storage for program and data files, and may include a hard disk drive, flash memory, a floppy disk drive along with associated removable media, a Compact Disk Read Only Memory (CD-ROM) drive, an optical drive, removable media cartridges, and other like storage media.

The user interface devices <NUM> can include any suitable user input device suitable to provide user input to the control electronics <NUM>. For example, the user interface devices <NUM> can include devices such as, for example, a touch-screen display/input device, a keyboard, a footswitch, a keypad, a patient interface radio frequency identification (RFID) reader, an emergency stop button, and a key switch.

The laser surgery system <NUM> can be configured to image and/or modify an intraocular target by scanning the focal point of the electromagnetic radiation beam in a particular area. For example, referring now to <FIG> and <FIG>, the laser surgery system <NUM> can be used to incise an anterior capsulotomy and/or a posterior capsulotomy in the anterior portion of a lens capsule <NUM>. The focal point of the electromagnetic radiation beam can be scanned to form an anterior capsulotomy closed incision boundary surface <NUM> that transects the anterior portion of the lens capsule <NUM>. Likewise, the focal point of the electromagnetic radiation beam can be scanned to form a posterior capsulotomy closed incision boundary surface <NUM> that transects the posterior portion of the lens capsule <NUM>.

The anterior and/or posterior closed incision boundary surfaces <NUM>, <NUM> can be designated using any suitable approach. For example, a plan view of the patient's eye can be obtained using the camera <NUM>. A capsulotomy incision designator <NUM> can be located and shown superimposed on the plan view of the patient's eye to illustrate the size, location, and shape of a planned capsulotomy relative to the patient's eye. The capsulotomy incision designator <NUM> can be manually defined by an operator of the laser surgery system <NUM> and/or the laser surgery system <NUM> can be configured to generate an initial capsulotomy incision designator <NUM> for operator verification and/or modification.

The anterior capsulotomy closed incision boundary surface <NUM> can be defined on a projection of the capsulotomy incision designator <NUM> such that the anterior capsulotomy closed incision boundary surface <NUM> transects the anterior portion of the lens capsule <NUM> at all locations around the anterior capsulotomy incision boundary surface <NUM> for all expected variations in the location of the anterior portion of the lens capsule <NUM> relative to the projection of the capsulotomy incision designator <NUM>. For example, a curve corresponding to the capsulotomy incision designator <NUM> can be projected to define an intersection with a minimum depth mathematical surface model (e.g., a spherical surface) defining a minimum expected depth configuration for the anterior portion of the lens capsule <NUM> with the resulting intersection being an anterior capsulotomy upper closed curve <NUM> that defines an upper boundary for the anterior capsulotomy closed incision boundary surface <NUM>. Likewise, the curve corresponding to the capsulotomy incision designator <NUM> can be projected to define an intersection with a maximum depth mathematical surface model (e.g., a spherical surface) defining a maximum expected depth configuration for the anterior portion of the lens capsule <NUM> with the resulting intersection being an anterior capsulotomy lower closed curve <NUM> that defines a lower boundary for the anterior capsulotomy closed incision boundary surface <NUM>. Alternatively, the focal point can be scanned using a low imaging-only power level (e.g., a power level sufficient to provide for imaging of the intraocular target via processing of the signal generated by the detection sensor <NUM> of the confocal detection assembly <NUM> without modifying the intraocular target) along the projection of the capsulotomy incision designator <NUM> while varying the depth of the focal point to determine the depth of the anterior lens capsule at a sufficient number of locations around the projection of the capsulotomy incision designator <NUM>. For example, <FIG> illustrates variation of intensity of the signal generated by the detection sensor <NUM> with variation in depth of the focal point with the maximum peak in intensity corresponding to the depth of the anterior portion of the lens. The measured depths of the anterior lens can then be used to determine suitable anterior capsulotomy upper and lower boundary curves <NUM>, <NUM> of the anterior capsulotomy closed incision boundary surface <NUM>.

In a similar fashion, the posterior capsulotomy closed incision boundary surface <NUM> can be defined on a projection of the capsulotomy incision designator <NUM> such that the posterior capsulotomy closed incision boundary surface <NUM> transects the posterior portion of the lens capsule <NUM> at all locations around the posterior capsulotomy incision boundary surface <NUM> for all expected variations in the location of the posterior portion of the lens capsule <NUM> relative to the projection of the capsulotomy incision designator <NUM>. For example, the curve corresponding to the capsulotomy incision designator <NUM> can be projected to define an intersection with a minimum depth mathematical surface model (e.g., a spherical surface) defining a minimum expected depth configuration for the posterior portion of the lens capsule <NUM> with the resulting intersection being a posterior capsulotomy upper closed curve <NUM> that defines an upper boundary for the posterior capsulotomy closed incision boundary surface <NUM>. Likewise, the curve corresponding to the capsulotomy incision designator <NUM> can be projected to define an intersection with a maximum depth mathematical surface model (e.g., a spherical surface) defining a maximum expected depth configuration for the posterior portion of the lens capsule <NUM> with the resulting intersection being a posterior capsulotomy lower closed curve <NUM> that defines a lower boundary for the posterior capsulotomy closed incision boundary surface <NUM>. Alternatively, the focal point can be scanned using a low imaging-only power level (e.g., a power level sufficient to provide for imaging of the intraocular target via processing of the signal generated by the detection sensor <NUM> of the confocal detection assembly <NUM> without modifying the intraocular target) along the projection of the capsulotomy incision designator <NUM> while varying the depth of the focal point to determine the depth of the posterior lens capsule at a sufficient number of locations around the projection of the capsulotomy incision designator <NUM>. The measured depths of the posterior lens capsule can then be used to determine suitable posterior capsulotomy upper and lower boundary curves <NUM>, <NUM> of the posterior capsulotomy closed incision boundary surface <NUM>.

While any suitable projection of the capsulotomy incision designator <NUM> can be used to define the anterior and/or posterior capsulotomy incision boundary surfaces <NUM>, <NUM>, in many embodiments an inverted cone shaped projection of the capsulotomy incision designator <NUM> is employed so as to maintain a suitable safety margin distance between the electromagnetic radiation beam, which converges to the focal point while propagating from the objective lens assembly <NUM> to the focal point, and the edge of the iris. Accordingly, in many embodiments, the posterior capsulotomy has a smaller diameter than a corresponding anterior capsulotomy for a given capsulotomy incision designator <NUM>, for example, as illustrated.

The laser surgery system <NUM> can be used to form any suitably-shaped capsulotomy. For example, while the anterior and the posterior capsulotomies in the illustrated embodiments are circular, any other suitable shape, including but not limited to, elliptical, rectangular, and polygonal can be formed. And, the anterior and/or the posterior capsulotomy can be shaped to accommodate any correspondingly suitably-shaped intraocular lens (IOL).

The laser surgery system <NUM> can be configured to generate image data concurrent with tissue treatment. For example, the focal point of the electromagnetic radiation beam can have an intensity sufficient to modify an intraocular target (e.g., eye tissue, an IOL) with a resulting portion of the electromagnetic radiation beam reflected from the focal point back to the detection sensor <NUM> of confocal detection assembly <NUM> used to generate a signal that is processed to generate image data corresponding to the focal point location.

By scanning the focal point in a pattern that crosses a boundary of an intraocular target, the detection sensor <NUM> can be used to concurrently generate a signal that can be processed to identify the location of the crossed boundary. For example, <FIG> illustrates variation of intensity of the signal generated by the detection sensor <NUM> with variation in depth of the focal point with the maximum peak in intensity corresponding to the depth of the anterior portion of the lens. The location of the crossed boundary can be used to control subsequent scanning of the focal point so as to reduce the amount of tissue that is treated. For example, when incising an anterior capsulotomy in the lens capsule, the focal point can be scanned in a scan pattern that is at least in part based on the location of the anterior portion of the lens as determined by processing the signal from the detection sensor <NUM> generated during a previous scan pattern.

<FIG> is a simplified block diagram of acts of a method <NUM> for adaptively scanning the focal point of the electronic radiation beam relative to a boundary of an intraocular target, according to many embodiments. The method <NUM> can be accomplished, for example, using any suitable system including any suitable laser surgery system described herein such as the laser surgery system <NUM>.

The method <NUM> includes scanning a focal point of the electromagnetic radiation beam in a first scan pattern so as to cross a boundary of an intraocular target (act <NUM>). In many embodiments, the scan pattern moves the focal point transverse to and/or parallel to the direction of propagation of the electromagnetic radiation beam. The intraocular target having the crossed boundary can be any suitable intraocular target including, for example, the anterior lens capsule, the posterior lens capsule, the crystalline lens, the cornea, the iris, an intraocular lens, and the limbus. Where a plurality of scan patterns is applied to create an incision surface (e.g., the closed incision boundary surface <NUM> shown in <FIG> and <FIG>), the scan patterns can be configured such that the electromagnetic radiation beam propagates to the focal point through unmodified eye tissue and/or IOL material. For example, the scan patterns can be configured and accomplished such that modification occurs in a generally deeper to shallower manner (e.g., posterior to anterior).

The method <NUM> further includes generating a signal indicative of the intensity of a portion of the electromagnetic radiation beam reflected from the focal point during the scanning of the focal point in the first scan pattern (act <NUM>). For example, because the first scan pattern crosses the boundary of the intraocular target, the signal generated by the detection sensor (e.g., such as the signal illustrated in <FIG>) and focal point position data for the first scan pattern can be processed to determine the location of the crossed boundary (act <NUM>) by, for example, identifying a signal variation consistent with the applicable boundary.

Having determined the location of where the first scan pattern crossed the boundary of the intraocular target, the focal point can be scanned in a second scan pattern that is configured at least in part based on the location where the first scan pattern crossed the boundary of the intraocular target (act <NUM>). For example, the second scan pattern can be configured to only extend beyond an estimated location of where the second scan pattern will cross the boundary of the intraocular target by predetermined amounts selected to account for possible variations in the estimated location of where the second scan pattern will cross the boundary in view of knowing where the first scan pattern crossed the boundary of the intraocular target. In many embodiments, the second scan pattern will be immediately adjacent to if not overlapped with the first scan pattern, thereby reducing the possible variation between the measured location where the first scan pattern crossed the boundary and the estimated location where the second scan pattern will cross the boundary. In many embodiments in which an incision surface is created, a series of subsequent scan patterns can be accomplished in which the location where one or more previous scan patterns crossed the boundary of the intraocular lens can be used to configured at least one of the subsequent scan patterns to, for example, minimize the tissue and/or material modified and/or increase the accuracy with regard to which tissue and/or material is modified.

<FIG> schematically illustrates repeated use of a location where a scan pattern for the focal point crossed a boundary of an intraocular target to configure a subsequent scan pattern. While <FIG> employs scan patterns having variation in the location of the focal point relative to the z-dimension (i.e., parallel to the direction of propagation of the electromagnetic radiation beam), the concept illustrated can be adapted to apply to any suitable scan pattern having, for example, variation in the location of the focal point relative to directions transverse to as well as transverse to and parallel to the direction of propagation of the electromagnetic radiation beam (e.g., x-direction variation, y-direction variation, and/or z-direction variation). An initial scan pattern <NUM> can be configured so as to extend between two locations <NUM>,<NUM> that are selected so that the initial scan pattern <NUM> crosses a boundary <NUM> for an intraocular target for all expected variations in the location of the boundary <NUM>. By processing the signal generated by the detection sensor <NUM> during the initial scan pattern <NUM> along with focal point location data for the initial scan pattern <NUM>, a location <NUM> where the initial scan pattern <NUM> crossed the boundary <NUM> can be identified.

A second scan pattern <NUM> can then be configured at least in part based on the location <NUM>. For example, end locations <NUM>, <NUM> for the second scan pattern <NUM> can be selected based on the location <NUM> so as to, for example, substantially minimize the length of the second scan pattern so as to minimize the amount of tissue and/or material treated. By processing the signal generated by the detection sensor <NUM> during the second scan pattern <NUM> along with focal point location data for the second scan pattern <NUM>, a location <NUM> where the second scan pattern <NUM> crossed the boundary <NUM> can be identified.

Any suitable subsequent scan pattern can be configured in a similar fashion. For example, by processing the signal generated by the detection sensor during a scan pattern <NUM> along with focal point location data tor the scan pattern <NUM>, a location <NUM> where the scan pattern <NUM> crossed the boundary <NUM> can be identified. End points <NUM>, <NUM> for a subsequent scan pattern <NUM> can be selected based on the location <NUM> so as to, for example, substantially minimize the length of the scan pattern <NUM> so as to minimize the amount of tissue and/or material treated. Accordingly, a series of scan patterns can be adaptively configured and applied using boundary location data for the intraocular target generated from one or more previous scan patterns.

<FIG> illustrates a series of scan patterns <NUM> that can be used to incise a surface that transects a boundary <NUM> of an intraocular target. In the illustrated embodiment, the scan patterns <NUM> are adaptively configured using boundary location data generated from one or more previous scan patterns of the series of scan patterns <NUM>, such as described above with respect to <FIG> and method <NUM>. Accordingly, the series of scan patterns <NUM> can be configured to generally extend beyond both sides of the boundary <NUM> by substantially uniform distances and thereby follow the general shape of the boundary <NUM>.

<FIG> illustrate scanning directions <NUM>, <NUM> that can be used to incise the series of scan patterns <NUM>. While any suitable scanning directions can be used, the illustrated directions <NUM>, <NUM> can be used to avoid having the electromagnetic radiation beam propagate through previously treated tissue/material prior to reaching the focal point.

In some embodiments, the capsulotomy scan may take longer than would be ideal due to the scan pattern being substantially longer in the z-depth dimension than the capsule to reduce the chances of incomplete cutting. For example, in some embodiments, the scan pattern may provide a <NUM> overlap to ensure incision through the lens capsule of the eye. Further, in some embodiments, laser spots may be smaller and thus may require more time to provide a continuous or nearly continuous incision. Accordingly some methods and systems may reduce the time for incising a capsulotomy by keeping the focus of an electromagnetic radiation beam on the capsular edge while incising so as to complete the incision using one or a few scans.

<FIG> illustrates an exemplary method <NUM> of controlling the scanning of a focal point of an electromagnetic radiation beam to incise the lens capsule and reduce overlap. At step <NUM>, an imaging prescan may be performed for aligning the focal point of an electromagnetic radiation beam. At step <NUM>, a location of the capsule surface may be identified. At step <NUM>, an electromagnetic radiation beam may be focused to a focal point at the identified location. At step <NUM>, electromagnetic radiation may be reflected from the focal point in response to step <NUM>. The reflected electromagnetic radiation may be measured <NUM> so as to generate a signal intensity. The measured signal intensity may be fed into a predictor algorithm block in software. The predictor block <NUM> identifies one of three conditions and issues an appropriate command. If the measured signal intensity is above an upper threshold value, predictor <NUM> may issue a command <NUM> to decrease a depth of the subsequent electromagnetic radiation focal point. If the measured signal intensity is below a lower threshold value, predictor <NUM> may issue a command <NUM> to increase a depth of the subsequent electromagnetic radiation focal point. If the measured signal intensity is above the lower threshold value and below the upper threshold value, the predictor <NUM> may issue command <NUM> to maintain a depth of the subsequent electromagnetic radiation focal point. Thereafter, method <NUM> proceeds to step <NUM> where the electromagnetic radiation beam is focused to the subsequent focal point. After step <NUM>, the method <NUM> may loop back to step <NUM> where the signal intensity of reflected electromagnetic radiation from the focal point is measured. Step <NUM>-<NUM> may be repeated until the planned capsulotomy is completed.

While method <NUM> is described with regard to a capsulotomy incision, the method may be applicable incisions of other intraocular targets. In these instances, the other target tissues might be the corneal surfaces or intra-corneal reference surfaces like the corneal epithelium, Bowman's layer, intrastromal layers, or the endothelium.

Method <NUM> may be performed by the systems and devices described above. For example, steps <NUM> and <NUM> may be performed using confocal imaging. As mentioned above, imaging and cutting may be performed concurrently using the same electromagnetic radiation beam. Accordingly, such a system may be used to adjust the focal depth onto the capsule surface as a treatment beam incises the capsule. In some embodiments, the capsulotomy can be achieved with only one scan. In other embodiments, the incision is performed by two or more scans. This may be preferable to a <NUM> overlap since a capsulotomy may be performed much faster with one or a few scans thereby reducing the possibility of inadvertent eye/lens movement relative to the treatment system during or between scans. Further, with fewer scans of a treatment beam, the energy transmitted into the eye by scanning the focal point of an electromagnetic radiation beam may be reduced.

The pre-scan <NUM> may provide an estimated location of the lens prior to incising tissue in order to align the laser with the lens capsule. The focal point of an electromagnetic radiation beam can be scanned using a low imaging-only power level (e.g., a power level sufficient to provide for imaging of the intraocular target without modifying the intraocular target). It may be scanned along a projection of an intraocular incision designer such as capsulotomy incision designer <NUM>. The depth of the focal point may be varied to determine a depth of the anterior lens capsule <NUM>. The intensity of the reflected signal, however, rises from near zero to a peak value over a z-scan distance of about <NUM> as can be seen in <FIG>; and the peak value may correspond to a depth of the anterior lens. Thus, locking onto the surface of the lens capsule may be somewhat challenging.

At step <NUM>, a treatment beam (e.g., a beam with a power level sufficient to provide for target modification and/or incision) may be focused to a focal point at the identified anterior surface of the lens capsule. In some embodiments, a single treatment beam pulse is delivered to the location. Alternatively, a plurality of pulses (e.g., <NUM> pulses) may be fired at each depth prior to adjustment. This may be preferable in some instances where adjustment for each pulse may be challenging for the z-scan device. In some embodiments, the size of a single pulse may be <NUM> long and about <NUM> wide. Further, in some embodiments, it may not be necessary to cut completely through the capsule in order to sufficiently weaken the capsule for removal.

Since, the lens capsule can move slightly during surgery, step <NUM> and an estimator/predictor block <NUM> may be used to make corrections to the z-depth in near real time as the focal point of a treatment beam is scanned around the capsulotomy. These steps may help ensure correct positioning of the focal point relative to the capsular bag. At step <NUM>, an intensity signal of reflected electromagnetic radiation from the focal point of the treatment beam is measured. Based on the intensity signal of the reflected electromagnetic radiation, the estimator/predictor block <NUM> may make adjustments to a focal point position when needed. As illustrated in <FIG>, the peak intensity value may correspond to a focal point positioned posterior to the lens capsule. In contrast, the low intensity values may correspond to a focal point positioned anterior to the lens capsule or positioned in the aqueous humor of the eye. The lens capsule has an intensity value between the peak intensity value and the intensity value of focal points positioned in the aqueous humor of the eye. Accordingly, an intensity range having an upper threshold and a lower threshold may be defined for indicating a position of the lens capsule of the eye. A measured intensity signal of reflected electromagnetic radiation that is above the upper threshold value may suggest that the focal point of the treatment laser was located within the lens of the eye and posterior to the lens capsule. Thus, the depth of a subsequent focal point of the treatment beam should be decreased. A measured intensity signal of reflected electromagnetic radiation that is below the lower threshold value may suggest that the focal point of the treatment laser was located within the aqueous humor and anterior to the lens capsule. Thus, the depth of a subsequent focal point of the treatment beam should be increased. When the measured intensity signal of reflected electromagnetic radiation is above the lower threshold and below the upper threshold, it may suggest that the focal point of the treatment was located on or sufficiently near the lens capsule of the eye. Hence, the depth of a subsequent focal point of the treatment beam may be maintained.

<FIG> illustrates exemplary focus profiles <NUM> located relative to a lens <NUM>, lens capsule <NUM>, and aqueous humor <NUM>. In the illustrated figure, intensity signals of reflected electromagnetic radiation from focus profiles <NUM> may be between the lower and upper threshold values and thus indicate a focal point sufficiently close to the lens capsule <NUM>. Accordingly, no depth adjustment may be necessary for subsequent focal points. The intensity signal of reflected electromagnetic radiation from focus profile <NUM> may be above the upper threshold value and thus indicates a focal point at too great a depth and within the lens <NUM>. Accordingly, estimator/predictor <NUM> may decrease a depth of a subsequent focal point. Further, the intensity signal of reflected electromagnetic radiation from focus profile <NUM> may be below the lower threshold value and thus indicates a focal point at insufficient depth and within the aqueous humor <NUM>. Accordingly, estimator/predictor <NUM> may increase a depth of a subsequent focal point.

As discussed above, in some embodiments, multiple pulses may be fired at a single depth prior to measuring and correcting a depth of subsequent pulses. In some embodiments, <NUM>-<NUM> pulses may be fired at a depth before measuring <NUM> and correcting with estimator/predictor <NUM>, for example. Further, in some embodiments, a z-depth can be dithered to provide phase information of the intensity signal so as to indicate an a proper depth to place the incision at least partially inside the lens capsule. In such an embodiment, a z-depth may be dithered from a posterior position toward an anterior position to avoid transmitting the beam through modified tissue. Further, in some embodiments, at the start of an incision, a treatment beam may be started inward of the defined capsulotomy. The initial incision may bulge or otherwise deform the tissue such that the capsule can move out of alignment. Thus, in some embodiments, a treatment beam may be focused within the lens and a focal point depth may be decreased until the focal point is positioned on or substantially close to the lens capsule. Thereafter, the focal point may be scanned along the projection of the planned capsulotomy and the depth may be adjusted according to the methods disclosed above.

<FIG> illustrates an exemplary scan <NUM> of the eye which is unwrapped. Scan <NUM> may include a lens <NUM>, lens capsule <NUM>, and aqueous humor <NUM>. Lens capsule <NUM> may be approximately <NUM> thick. The dotted lines <NUM> illustrate a tolerance of <NUM> which may be used for some incisions. Such an incision may however, take more time due to the large overlap. Incision <NUM> may illustrate an incision performed by one of the above methods, such as method <NUM>. In some embodiments, incision <NUM> may be performed with depth adjustments between each pulse. In other embodiments, incision <NUM> may be performed with depth adjustments between a plurality of pulses. In some embodiments, incision <NUM> may include pulses dithered in a z-direction. As can be appreciated, such a scan <NUM> may be performed with one or a few scans along a planned capsulotomy.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (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.

Claim 1:
A system for modifying an intraocular target of an eye, the system comprising:
an electromagnetic beam source (<NUM>) configured to generate a treatment beam;
optics (<NUM>) configured to focus the treatment beam to a focal point and scan the focal point to locations in the eye;
a detector (<NUM>) configured to receive electromagnetic radiation reflected from a location of the treatment beam focal point and to measure an intensity signal of the reflected electromagnetic radiation;
a controller (<NUM>, <NUM>) coupled with the optics and the detector and configured to identify a subsequent location of the focal point of the treatment beam using a feedback loop based in part on the measured intensity signal of the electromagnetic radiation reflected from the focal point location, wherein the focal point is scanned towards the subsequent location and the tissue is altered at the subsequent location with the treatment beam.