[go: up one dir, main page]

WO1999038443A1 - Procede de balayage laser haute frequence - Google Patents

Procede de balayage laser haute frequence Download PDF

Info

Publication number
WO1999038443A1
WO1999038443A1 PCT/US1999/002015 US9902015W WO9938443A1 WO 1999038443 A1 WO1999038443 A1 WO 1999038443A1 US 9902015 W US9902015 W US 9902015W WO 9938443 A1 WO9938443 A1 WO 9938443A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser beam
tissue
scanning
ablation
ablating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1999/002015
Other languages
English (en)
Inventor
Fuqian Tang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
LaserSight Technologies Inc
Original Assignee
LaserSight Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by LaserSight Technologies Inc filed Critical LaserSight Technologies Inc
Priority to AU24861/99A priority Critical patent/AU2486199A/en
Publication of WO1999038443A1 publication Critical patent/WO1999038443A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting in contact-lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/007—Methods or devices for eye surgery
    • A61F9/008—Methods or devices for eye surgery using laser
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting in contact-lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/007—Methods or devices for eye surgery
    • A61F9/008—Methods or devices for eye surgery using laser
    • A61F9/00802—Methods or devices for eye surgery using laser for photoablation
    • A61F9/00804—Refractive treatments
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
    • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
    • A61B2018/2035—Beam shaping or redirecting; Optical components therefor
    • A61B2018/20351—Scanning mechanisms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/18—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves
    • A61B18/20—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by applying electromagnetic radiation, e.g. microwaves using laser
    • A61B2018/2035—Beam shaping or redirecting; Optical components therefor
    • A61B2018/20351—Scanning mechanisms
    • A61B2018/20359—Scanning mechanisms by movable mirrors, e.g. galvanometric
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting in contact-lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/007—Methods or devices for eye surgery
    • A61F9/008—Methods or devices for eye surgery using laser
    • A61F2009/00844—Feedback systems
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting in contact-lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/007—Methods or devices for eye surgery
    • A61F9/008—Methods or devices for eye surgery using laser
    • A61F2009/00861—Methods or devices for eye surgery using laser adapted for treatment at a particular location
    • A61F2009/00872—Cornea
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting in contact-lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/007—Methods or devices for eye surgery
    • A61F9/008—Methods or devices for eye surgery using laser
    • A61F2009/00897—Scanning mechanisms or algorithms

Definitions

  • This invention relates generally to a method of ablating tissue, and more particularly, it relates to a method of ablating tissue by scanning of a laser beam having a high repetition rate on the tissue to be ablated.
  • an ablating laser beam is used to ablate portion(s) of layer(s) of a cornea to reshape the curvature of the surface of the cornea.
  • the curvature is lessened, i.e., made more flat.
  • the curvature is made more prominent to correct a hyperopic eye, and is made more round to correct an astigmatic eye.
  • the scanning, or masking combined with scanning achieves smoother, i.e., having fewer ridges or steps in the remaining corneal surface than with - 2 - respect to a non-scanning approach, i.e., by solely masking a large beam diameter laser.
  • a scanning technique utilizes a scanning mechanism to scan or move the laser beam along the surface of the tissue being ablated.
  • a galvanometer scanner having motorized rotating mirror(s) is used.
  • a controller controls the position of the rotating mirror(s) to move the "spot" of the laser beam (i.e., the point at which the laser beam is incident on the surface of the cornea) to each of predetermined ablation points of a scanning pattern to achieve the desired ablation profile.
  • an ablation is performed at each of a plurality of ablation points along a set pattern on the surface being ablated in accordance with a desired final surface contour.
  • the laser beam is pulsed once at each ablation point.
  • Each pulse of the laser beam applies a given level of energy, depending on, inter alia, the output energy per pulse of the laser and the "spot size" of the laser beam, to the corneal tissue, sufficient to thereby, excise or ablate (i.e., remove) a volume of the corneal tissue. More than one pulse can be combined to provide a deeper or smoother overall effect, but each pulse in and of itself is sufficient to ablate a given amount of tissue.
  • the controller of the scanning mechanism provides synchronization between the scanning speed of the scanner, i.e., the rotating mirror(s), and the repetition rate of output beam of the laser in order to ablate tissue at only the predetermined ablation points, but not during movement of the spot from one ablating point to the next.
  • the required duration of the refractive surgery is typically limited by the scanning speed, i.e., the speed at which the scanning mirror(s) can be accurately positioned between each laser pulse.
  • the maximum scanning speed of currently available galvanometer scanners is on the order of about 300 to 400Hz, which is considerably slower than the maximum repetition rate of a - 3 - laser.
  • a longer surgery duration runs the risk of added movement of the tissue, i.e., the eye, at least at some point during the surgery.
  • techniques to track movement of the eye are known, movement is nevertheless to be avoided.
  • Conventional scanning systems typically operate between about 10Hz to 40Hz, and perhaps as high as 100Hz to 200Hz.
  • a solid state laser is capable of much lower per pulse energy than an excimer laser.
  • a solid state laser can be pulsed at a much higher repetition rate (e.g., 1 KHz to 50 KHz or 100KHz or more) than an excimer laser, albeit a much higher speed than possible with conventional scanning techniques.
  • E the per pulse energy of the laser
  • R P the repetition rate of the laser beam pulses.
  • E the per pulse energy of the laser
  • R P the repetition rate of the laser beam pulses.
  • E the per pulse energy of the laser
  • R P the repetition rate of the laser beam pulses.
  • Fig. 4 shows a conventional laser beam delivery system 400 having a laser head 412.
  • the laser beam delivery system 412 generates a pulsed ablating laser beam 414 and includes a combination of optical elements 426 that attenuate, shape, direct and otherwise control the ablating laser beam 414 to the various ablation points or spots in an ablation zone predetermined on tissue to be ablated, e.g., a cornea 436 to be treated.
  • the computer system 418 controls the laser head 412 and the scanning device 416 to deliver the laser beam 432 at the corneal surface 434 according to a predetermined ablation profile.
  • the diameter of the laser beam spot of the laser beam 432 incident on the cornea 436 is controllable to vary within a range by focusing optics of the optics system 426 and is scanned on the cornea 436 by a scanning device or mechanism 416, and delivered to the corneal surface 434 via a reflecting mirror 430.
  • the diameter of the laser beam spot is selected for the energy density required to be delivered to the corneal surface 434 to achieve the desired amount of tissue removal and the depth of ablation, but in any event is typically in excess of a minimum amount necessary to cause ablation by each pulse.
  • the laser delivery system 400 may further include a feedback system (not shown) which continuously monitors and reports the actual ablation being made at corneal surface 434, in real time during the corneal ablation operation, to the computer system 418, which uses the information to further control the laser head 412 and scanning device 416 to achieve the desired resulting ablation profile.
  • a feedback system (not shown) which continuously monitors and reports the actual ablation being made at corneal surface 434, in real time during the corneal ablation operation, to the computer system 418, which uses the information to further control the laser head 412 and scanning device 416 to achieve the desired resulting ablation profile.
  • the scanning device 416 may include at least one scanning mirror driven by at least one electrical galvanometer (servo-actuated limited- rotation motors).
  • the scanning device may be, for example, a galvanometer - 5 - scanner commercially available from General Scanning, Inc of Watertown, Massachusetts.
  • the laser beam is reflected off and directed by the scanning mirror on to the desired ablation point on the corneal surface 434.
  • the rotation of the scanning mirror is controlled by the galvanometer, which in turn receives drive signal from a drive electronic typically controlled by the computer system 418.
  • a scanning mirror attached to a galvanometer is required for movement of the laser beam along an axis.
  • one mirror/galvanometer combination may be used for the movement in x-axis direction, and another combination for the y-axis direction.
  • the aperture of each of the mirrors must accommodate the respective movements of the beam caused by the other mirror(s).
  • An ablation pattern such as shown in Fig. 5, may be generated, and used to generate the x-y drive signals.
  • Each of the dots shown in Fig. 5 represents an ablation point of a layer of an ablation zone 535 within a cornea 536, and each of the lines 501 to 510 represent a particular scan line within an overall ablation zone 536.
  • Layer 535 represents one of a plurality of layers of tissue being ablated.
  • the scanning may be accomplished in a stepwise fashion (step scanning) in which the path between each ablation point is unimportant.
  • the mirrors are moved in random paths between the ablation points (shown as dotted lines with arrows 537).
  • the scanning may also be accomplished a raster scanning in which the mirror(s) are swept, at a constant velocity across scan lines (shown as solid lines with arrows 501-510) which are at a fixed angular range, within the ablation zone 535.
  • the scanning speed of step scanning is related to the step time which is the sum of the time required for the mirror to travel from one ablation point to another and the settling time of the mirror.
  • the settling time is the time required for the mirror to come to a stop within a settling tolerance, centered around the final intended position, i.e., a particular ablation point.
  • - 6 - ln a raster scanning
  • the scanning speed is related to the active scan time, which is the scan period less the retrace time.
  • the scan period is reciprocal of the scanning frequency.
  • the retrace time is the time required for the mirror to return to the start of the next scan line after completely scanning a scan line.
  • the scanning frequency and the retrace time are limited by the ability of the mirror(s) to accelerate/decelerate to and from the constant nominal velocity between sweeps.
  • the step time and the acceleration/deceleration of the mirror(s) are largely related to the rotational inertia of the mirror.
  • the rotational inertia depends on the physical size and the required rigidity of the mirror.
  • a minimum rigidity is required in order to avoid excessive resonance of the mirror.
  • Fig. 6 shows an example of the high repetition rate capability of a solid state laser in general as compared to a relatively low repetition rate of the same solid state laser as limited by conventional scanning mechanisms as shown in Fig. 7.
  • the laser energy density of each of the pulses must be above the photoablation threshold (PAT).
  • the PAT is 60-120mJ/cm 2 for a UV-laser (193-215 nm wavelength), 200-600mJ/cm 2 for an IR-laser (2.5-3.2 ⁇ m wavelength), and 50mJ/cm2 for an ArF excimer laser (193nm wavelength).
  • the energy density (I) is defined as: - 7 -
  • Fig. 8 shows a typical process flow of a conventional scanning laser system in which the laser pulse rate is synchronized to the scanning rate of the scanning mirror(s).
  • an ablation profile is determined to treat a specific condition of a particular patient's eye, e.g., myopia, hyperopia, or astigmatism.
  • the ablation profile may include, for example, the points (or spots) on the corneal surface for each layers of the cornea to be ablated, to achieve the desired final shape of the corneal surface.
  • the scanning mirror(s) is (are) moved to one of the points to be ablated. Once the laser beam spot is at one of the ablation points, the laser is allowed to pulse in step 804, and thus, a volume of corneal tissue commensurate with the energy level of the laser pulse is ablated.
  • the moving of the mirror(s) and the pulsing of the laser are repeated until it is determined that all ablation points has been ablated in step 805.
  • the laser is forced to be pulsed at the scanning speed, i.e., to much less than 300-400Hz, and is typically in the range of 10Hz to 40Hz.
  • a method of ablating tissue with a scanning laser beam at an increased effective repetition rate is provided.
  • a laser is pulsed at a pulse sequence, of a variable repetition rate, having one or more first time duration during which the laser is pulsed at a high repetition rate and one or more second time duration during which the laser outputs no pulses.
  • the scanning mirrors are either stationary or are moved within a very small confines.
  • the scanning mirror(s) make a major movement so as to move the laser beam spot across the surface of the tissue from one ablation point to an another ablation point substantially apart from each other.
  • the present invention is particularly useful for ablating tissue with a scanning laser beam of a low power solid-state laser, for example, a flash lamp or diode pumped UV laser or an IR laser. - 9 -
  • a scanning laser beam of a low power solid-state laser for example, a flash lamp or diode pumped UV laser or an IR laser.
  • Fig. 1 is a graphical representation of an examplary variable repetition rate ablation pulse sequence of the output pulses of a solid state laser in accordance with the principles of the present invention
  • Fig. 2 is a flow diagram depicting an exemplar embodiment of the method of scanning laser beam at high repetition rate in accordance with the principles of the present invention
  • Fig. 3 is a flow diagram depicting an another exemplar embodiment of the method of scanning laser beam at high repetition rate in accordance with the principles of the present invention
  • Fig. 4 is an illustrative functional diagram of a conventional scanning laser refractive surgery system
  • Fig. 5 is an illustrative example of a scanning pattern depicting scan lines and ablation points of a ablation zone of a cornea being treated by a conventional scanning laser refractive surgery system;
  • Fig. 6 is a graphical representation of the output pulses of a conventional high repetition rate laser
  • Fig. 7 is a graphical representation of the output pulses of a high repetition rate laser limited by the slow scanner speed of a conventional scanning laser system.
  • Fig. 8 is a flow diagram depicting a conventional method of scanning laser beam.
  • the present invention relates to laser ablation techniques of human or animal tissue in - 10 - general.
  • the principles of the present invention may be applied in both photo-ablation and photo-coagulation techniques for reshaping the surface of a cornea, including, as examples but not limited to, laser refractive keratectomy (e.g. photorefractive keratectomy or PRK, PRK after radial keratomy, laser keratectomy with mircrokeratome, intrastromal photodisruption and laser in-situ keratomileusis or LASIK), laser therapeutic keratectomy, and laser lamellar resection.
  • laser refractive keratectomy e.g. photorefractive keratectomy or PRK, PRK after radial keratomy
  • laser keratectomy with mircrokeratome keratectomy with mircrokeratome
  • the present invention results from a realization that the operation time of a refractive laser surgery using a solid state laser can be shortened if the laser is allowed to pulse at a higher repetition rate, thus, achieving a high average power.
  • the total operation time (T 0 ) of a laser refractive surgery can be expressed as:
  • T 0 DW 4 /P (1 ), where D is the desired diopter correction, W is the correction zone diameter, i.e., the size of the area to be ablated, and P is the laser average power which can be further expressed as:
  • E the per-pulse energy of the laser
  • R p the repetition rate (or the pulse rate) of the laser.
  • equation (1 ) can be expressed as:
  • T 0 DW 4 /ER P (3).
  • the repetition rate R P of the laser is typically synchronized to match the scanning speed R s of the scanning mechanism.
  • equation (3) becomes:
  • a solid state laser can be pulsed at repetition speed up to
  • the scanning speed e.g. 400Hz if run at the highest possible conventional scanning speed
  • the surgery time, according to equation (4) above, would be T s (DW 4 /E)/400 seconds.
  • Fig. 1 shows a graphical representation of an examplary variable high repetition rate ablation pulse sequence of ablating pulses of a solid state laser, in accordance of the principles of the present invention.
  • sequence of ablating pulses at a high repetition rate as shown in Fig. 1 can be generated using, for example and not as a limitation, an electronic control (e.g., computer-controlled power supply to the laser or the optics), mechanical shutter, or any other suitable means to control the application of the ablating laser pulses at the corneal surface.
  • an electronic control e.g., computer-controlled power supply to the laser or the optics
  • mechanical shutter or any other suitable means to control the application of the ablating laser pulses at the corneal surface.
  • the repetition rate of the laser pulses during the ON time periods t s are greater than the scanning rate of the scanning mechanism between otherwise conventional ablation points.
  • the scanning mirror(s) either remain substantially stationary or is (are) made to move slightly within a very small proximity of an ablation point.
  • the amount of mirror movement during the ON time periods t s is dependent on the energy level of the individual laser pulses. For instance, the scanning mirror does not need to move at all if each individual laser pulse - 12 - has relatively low energy, such as it is the case with a solid state laser. Of course, the energy density of each pulse should exceed the photo-ablation threshold (PAT). However, with the ability to provide a larger number of ablating laser pulses within a short period of time, the energy may be much lower per pulse and in fact approach the PAT level itself and yet still be quite effective overall.
  • PAT photo-ablation threshold
  • number of ablating pulses may be irradiated on any particular ablation point without the accumulated ablation depth being caused to be made too deep before the scanner moves on (during the OFF time period T) to a next ablation point.
  • each pulse has a considerable amount of energy, e.g., if a conventional excimer laser is used, at higher power, movement of scanning mirror(s) may be necessary between each ablating pulse in order to not ablate tissue too deeply at any one particular ablation point.
  • movement of scanning mirror(s) between individual ablating laser pulses may be sub-ablation point increments, i.e., to be within a close proximity of a single ablation point in a given ablation pattern, an effectively high scanning rate can result.
  • the thickness of the tissue to be ablated is divided into a number of layers, each layer being ablated individually in a typical conventional scanning laser system.
  • the movement (and/or the number of movements) of the scanning mirror(s) during any one ON time period t s may be further minimized by ablating several layers at a time (i.e., within that ON time period t s ).
  • slight movements of the scanning mirror(s) between the high repetition rate ablation pulses in accordance with the principles of the present invention may provide a smoother ablated surface by promoting significant (e.g., over 80%) overlaps of the laser beam spots generated by each ablating laser pulse, thus, avoiding sharp steps or ridges that might - 13 - otherwise be created by a non-overlapping or less overlapping single pulse per ablation point techniques.
  • the pulse sequence according to the present invention may include more than one ON time period t s .
  • the scanning mirror makes a major movement across a larger distance, e.g., from one ablation point to another.
  • the laser pulses are absent, either by preventing the pulses from being output from the laser and/or by preventing ablating laser pulses from reaching the cornea or other tissue being ablated.
  • the pulse sequence shown in Fig. 1 may be determined and fixed at the outset of a surgery, or can be dynamically determined during the operation, taking into account information provided by, e.g., a feedback system which monitors and reports the actual amount of ablation which has occurred being made in real time.
  • Fig. 2 shows an exemplary embodiment of the present invention wherein the high repetition pulse sequence is fixedly determined at the outset of the surgery.
  • an ablation profile for the desired reshaping of cornea is determined in step 201.
  • a pulse sequence is generated to achieve the ablation of the cornea in accordance with the desired ablation profile while minimizing the movements (and/or the frequency thereof) between each laser pulse.
  • the pulse sequences are determined based on such factors as, for example, the energy level of the laser and/or the number of iayer(s) (both total and per scan) of cornea to be ablated.
  • the pulse sequence generated in step 202 is similar to the sequence depicted in Fig. 1 , and includes one or more ON time periods t s and OFF time periods T.
  • Each OFF time period T is determined from the ablation profile, and preferably corresponds to the - 14 - minimum step time required to move the scanning mirror(s) from one ablation point of the ablation profile to the next.
  • Each ON time period t s is determined from the desired operation time T 0 using the aforementioned equation (3).
  • T 0 DW 4 /ER P
  • the effective repetition rate R P can be determined given the desired operation time T 0 and the desired diopter correction D, the ablation zone width W, and the per pulse energy of the laser, all of which are known.
  • the duration and the pulse repetition rate for each ON time period t s can be determined by subtracting the sum of all OFF time periods ⁇ T from the desired operation time T 0 , resulting in the sum of all ON time periods ⁇ t s . Using the ratio, ⁇ T/
  • a control system determines and carries out the desired ablation sequence by providing appropriate control signals to the low power high repetition rate laser, to the scanner, and/or to the optics.
  • the control system reads the pulse sequence to determine whether the current time period is an ON time period t s or an OFF time period T according to the timing of the desired pulse sequence.
  • the control system sends appropriate control signals to the low power laser, the scanner and/or the optics to allow the ablating pulses of the laser beam to reach the tissue at a predetermined repetition rate R P .
  • the repetition rate R P may be, for example, as high as the maximum repetition rate that the laser is capable of, but will depend on other factors, e.g., the energy level of the laser per unit area as applied to the tissue.
  • the control signals may be, for example, a start pulse signal to the laser head and/or a signal to open a mechanical shutter to allow the ablating pulses of the laser beam to reach the corneal tissue.
  • control system also sends an appropriate control signal to the scanner to prevent significant movement of the scanning mirror(s), or to only allow slight movement(s) of the mirror(s) around a close vicinity of any particular ablation point.
  • step 204 if the control system instead determines that the current period according to the pulse sequence is an OFF time period T, then the control system will send appropriate control signals to the low power laser, the scanner, and/or the optics to prevent ablating pulses of the laser beam from reaching the corneal surface for that duration of time.
  • step 208 the control system sends the appropriate signals to the scanner to cause the scanning mirrors to make a significant or major movement in order to move the spot of the laser beam across the ablation zone towards the next ablation point.
  • Fig. 3 shows an another exemplary embodiment of the present invention wherein a pulse sequence is generated, and is dynamically updated, by the control system during the ablation procedure in light of information provided by a feedback system.
  • Fig. 3 The embodiment of Fig. 3 is similar in its flow as the embodiment as described in reference to Fig. 2. However, in Fig. 3, a feedback system monitors and reports in real time the status of the actual ablation being performed. The control system, upon being provided with the feedback information, performs an ongoing comparison between the status of the actual ablation with the predetermined desired ablation profile. - 16 - In particular, steps 201 to 208 are substantially as described with respect to Fig. 2. However, as shown in step 309 of Fig. 3, the control system compares, preferably after each ON time period t s or each OFF time period T, compares the status of actual ablation with the desired ablation profile.
  • step 202a the pulse sequence is updated in order to more closely track the desired ablation profile by, for example, modifying the duration of each ON time periods t s or each OFF time period T and/or modifying the repetition rate R P of the laser pulses.
  • a solid state (or excimer) laser is capable of being pulsed at a repetition rate R P of 2KHz, and a scanning mechanism has a maximum scanning speed of, e.g., 350Hz.
  • the scanning rate would simply be 350Hz.
  • the principles of the present invention make use of the increased pulse capability of the source laser to provide an ablation technique having an effective ablation rate which is much greater than, e.g., the 350Hz maximum speed of the scanner.
  • the effective repetition (ablation) rate R PE would be about equal to the ablation pulse repetition rate R P (i.e., 2000Hz) multiplied by the duty cycle (i.e., 50% or V.).
  • the inventive scanning technique utilizing an ablation pulse sequence in accordance with the principles of the present invention achieves an effective ablation rate R PE that is not limited by the scanning speed of the scanning mirror(s).

Landscapes

  • Health & Medical Sciences (AREA)
  • Ophthalmology & Optometry (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Optics & Photonics (AREA)
  • Surgery (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Physics & Mathematics (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Laser Surgery Devices (AREA)

Abstract

L'invention concerne un procédé d'ablation de tissu par balayage au laser (432), selon un taux d'ablation efficace augmenté, qui consiste à utiliser un laser à semiconducteurs pulsé via une séquence d'impulsions à parties de fréquence de répétition variables. Par exemple, pendant une ou plusieurs premières périodes de temps (T) de la séquence d'impulsions, le laser est pulsé à une fréquence de répétition plus rapide que celle autorisée par un mécanisme de balayage et, pendant une ou plusieurs secondes périodes de temps (T), aucune impulsion laser n'est fournie au tissu. Selon une variante, pendant la ou les premières périodes de temps, le ou les miroirs de balayage (416) sont fixes ou déplacés dans des espaces très limités. Selon la même variante, durant la ou les secondes périodes de temps, la possibilité d'un mouvement majeur du ou des miroirs en question existe, suffisamment pour déplacer le faisceau laser ponctuel sur la surface du tissu, depuis un premier point d'ablation vers un second point d'ablation sensiblement distant du premier point. Le procédé est particulièrement utile pour l'ablation de tissu au faisceau laser (432) émanant d'un laser à semiconducteurs de faible puissance, par exemple un laser UV pompé par lampe-éclair ou diode, ou un laser infrarouge pompé par lampe-éclair ou diode, ou encore une diode laser.
PCT/US1999/002015 1998-02-03 1999-01-29 Procede de balayage laser haute frequence Ceased WO1999038443A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU24861/99A AU2486199A (en) 1998-02-03 1999-01-29 Scanning method of high frequency laser

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US7355398P 1998-02-03 1998-02-03
US60/073,553 1998-02-03

Publications (1)

Publication Number Publication Date
WO1999038443A1 true WO1999038443A1 (fr) 1999-08-05

Family

ID=22114390

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1999/002015 Ceased WO1999038443A1 (fr) 1998-02-03 1999-01-29 Procede de balayage laser haute frequence

Country Status (2)

Country Link
AU (1) AU2486199A (fr)
WO (1) WO1999038443A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1649843A1 (fr) * 2004-10-22 2006-04-26 Ligi Tecnologie Medicali S.p.A. Laser photoablatif avec contrôle de la fréquence d'emission des pulses.
WO2008055698A1 (fr) * 2006-11-10 2008-05-15 Carl Zeiss Meditec Ag Dispositif de traitement de correction d'un défaut visuel de l'oeil par opération, procédé de production de données de commande pour ce dispositif et procédé de correction d'un défaut visuel de l'oeil par opération
EP2217187A1 (fr) * 2007-11-07 2010-08-18 Abbott Medical Optics Inc. Système et procédé de balayage d'un faisceau laser à impulsions
US8685006B2 (en) 2006-11-10 2014-04-01 Carl Zeiss Meditec Ag Treatment apparatus for surgical correction of defective eyesight, method of generating control data therefore, and method for surgical correction of defective eyesight

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5098426A (en) * 1989-02-06 1992-03-24 Phoenix Laser Systems, Inc. Method and apparatus for precision laser surgery
US5178617A (en) * 1991-07-09 1993-01-12 Laserscope System for controlled distribution of laser dosage
US5620436A (en) * 1994-09-22 1997-04-15 Chiron Technolas Gmbh Ophthalmologische Systeme Method and apparatus for providing precise location of points on the eye
US5645550A (en) * 1994-04-08 1997-07-08 Chiron Technolas Gmbh Ophthalmologische System Method and apparatus for providing precise location of points on the eye

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5098426A (en) * 1989-02-06 1992-03-24 Phoenix Laser Systems, Inc. Method and apparatus for precision laser surgery
US5178617A (en) * 1991-07-09 1993-01-12 Laserscope System for controlled distribution of laser dosage
US5645550A (en) * 1994-04-08 1997-07-08 Chiron Technolas Gmbh Ophthalmologische System Method and apparatus for providing precise location of points on the eye
US5620436A (en) * 1994-09-22 1997-04-15 Chiron Technolas Gmbh Ophthalmologische Systeme Method and apparatus for providing precise location of points on the eye

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1649843A1 (fr) * 2004-10-22 2006-04-26 Ligi Tecnologie Medicali S.p.A. Laser photoablatif avec contrôle de la fréquence d'emission des pulses.
WO2008055698A1 (fr) * 2006-11-10 2008-05-15 Carl Zeiss Meditec Ag Dispositif de traitement de correction d'un défaut visuel de l'oeil par opération, procédé de production de données de commande pour ce dispositif et procédé de correction d'un défaut visuel de l'oeil par opération
US8685006B2 (en) 2006-11-10 2014-04-01 Carl Zeiss Meditec Ag Treatment apparatus for surgical correction of defective eyesight, method of generating control data therefore, and method for surgical correction of defective eyesight
US9370445B2 (en) 2006-11-10 2016-06-21 Carl Zeiss Meditec Ag Treatment apparatus for surgical correction of defective eyesight, method of generating control data therefore, and method for surgical correction of defective eyesight
US10098784B2 (en) 2006-11-10 2018-10-16 Carl Zeiss Meditec Ag Treatment apparatus for surgical correction of defective eyesight, method of generating control data therefore, and method for surgical correction of defective eyesight
US10390994B2 (en) 2006-11-10 2019-08-27 Carl Zeiss Meditec Ag Treatment apparatus for surgical correction of defective eyesight, method of generating control data therefore, and method for surgical correction of defective eyesight
US11103381B2 (en) 2006-11-10 2021-08-31 Carl Zeiss Meditec Ag Treatment apparatus for surgical correction of defective eyesight, method of generating control data therefore, and method for surgical correction of defective eyesight
EP2217187A1 (fr) * 2007-11-07 2010-08-18 Abbott Medical Optics Inc. Système et procédé de balayage d'un faisceau laser à impulsions

Also Published As

Publication number Publication date
AU2486199A (en) 1999-08-16

Similar Documents

Publication Publication Date Title
US5599340A (en) Laser beam ophthalmological surgery method and apparatus
US7077838B2 (en) Variable repetition rate firing scheme for refractive laser systems
US6755818B2 (en) Method and system for laser treatment of refractive errors using offset imaging
EP1389967B1 (fr) Appareil de traitement de la presbytie et d'autres affections de l'oeil, mettant en oeuvre des lasers couples par fibres
US7275545B2 (en) Methods and apparatus for presbyopia correction using ultraviolet and infrared lasers
US6745775B2 (en) Methods and apparatus for presbyopia treatment using a scanning laser system
US5556395A (en) Method and system for laser treatment of refractive error using an offset image of a rotatable mask
EP1549237B1 (fr) Modelisation thermique permettant une reduction des temps de chirurgie refractive au laser
JPH10510184A (ja) 除去放射の環状ビームを用いる角膜再整形
EP2094209B1 (fr) Système pour procédure laser à balayage commandée par opérateur conçue pour le retrait d'épithélium sur grande surface
WO2013126316A1 (fr) Méthode et appareil de chirurgie ophtalmique par faisceau laser
JPH0377553A (ja) 光制限用マスクを使用するレーザー再整形システム
US7582081B2 (en) Systems and methods for corneal surface ablation to correct hyperopia
JP7525975B2 (ja) 角膜幹細胞の選択的レーザ刺激
WO1999038443A1 (fr) Procede de balayage laser haute frequence
US7918846B2 (en) Method and system for laser treatment of refractive errors using offset imaging
EP1649843B1 (fr) Laser photoablatif avec contrôle de la fréquence d'emission des pulses.
AU671668B2 (en) Apparatus for modifying the surface of the eye through large beam laser polishing and method of controlling the apparatus
CA2296513A1 (fr) Systemes et procedes d'ablation de surface corneenne afin de corriger une hypermetropie
EP3993746A1 (fr) Correction réfractive de la cornée à l'aide d'un traitement de surface après remodelage de la cornée

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AU AZ BA BB BG BR BY CA CH CN CU CZ DE DK EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT UA UG UZ VN YU ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW SD SZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
NENP Non-entry into the national phase

Ref country code: KR

REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase