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
• • 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 to an apparatus and method for performing corneal refractive surgery to reshape the corneal surface of the eye and more particularly, to an apparatus and method for scanning a laser beam for smooth corneal reshaping.
• FIG. 1 is a schematic illustration of a conventional laser scanning method utilized to reshape a cornea.
• Each corneal layer 10 is ablated by delivering onto the cornea pulsed laser beams at ablation points 12 forming rows 14.
• the ablation points 12 are delivered with a step size S1 maintained between centers of adjacent ones of the laser ablation points 12.
• the step size S1 forms columns 14 of ablation points 12.
• the step sizes S1 and S2 may be equal or one may be greater than the other.
• ridges may be formed in the remaining corneal tissue when centers of laser beam ablation points 12 of two or more successive corneal layers 10 repeatedly cause ablation of the same spot on the cornea, or repeatedly miss other spots, or when both of these events occur.
• the starting point of each row 14 of ablation points 12 is randomized as shown in FIG. 2. This creates non-linear columns 15a of ablation points 12.
• the orientation or direction of rows 14 of ablation points 12 is rotated with respect to the previous corneal laser 10 by any arbitrary amount ⁇ , as shown in FIG. 3.
• the smoothness of the cornea after layers 10 of corneal tissue are removed is improved. Since the locations of the rows 14 of laser beam ablation points 12 is randomized, the chances of ablation points repeatedly hitting or missing the same relative point on the cornea is reduced somewhat.
• the apparatus includes a scanner to move a laser beam across a layer to be ablated.
• a processor determines a first plurality of ablation points substantially within the layer to be ablated. Each of the first plurality of ablation points is defined by a center of the laser beam.
• the processor determines a second plurality of ablation points to be ablated by the laser beam.
• Each of the second plurality of ablation points is defined by a center of the laser beam, and each of the second plurality of ablation points is disposed at a location linearly offset from a midpoint point between two adjacent ablation points of the first plurality of ablation points in a direction normal to a line defined by the two adjacent ablation points.
• FIG. 1 is an enlarged illustration of a conventional scanning method for laser ablation in which laser beam ablation points are distributed evenly in the layer to be ablated;
• FIG. 2 is an enlarged illustration of a conventional scanning method for laser ablation in which the starting locations of rows of ablation points are selected randomly;
• FIG. 3 is an enlarged illustration of a conventional scanning method for laser ablation in which the direction of rows of laser beam ablation points is rotated with respect to a previous ablation layer;
• FIG. 4 is an enlarged illustration of laser beam ablation points determined by a scanning method provided in accordance with the principles of the present invention
• FIG. 5 shows two subsequent ablation layers with the locations of laser beam ablation points determined in accordance with the scanning method of the invention
• FIG. 6 is an enlarged illustration of overlapping laser beam ablation points which result from the scanning method of FIG. 4;
• FIG. 7 is schematic illustration of an apparatus for re-profiling a surface of the eye, provided in accordance with the invention.
• FIG. 8 is a flow chart for determining ablation points by the scanning method of the invention.
• each corneal layer is ablated by delivering rows of pulsed laser beam ablation points onto the cornea.
• step size S1 between centers of adjacent laser beam ablation points 24.
• step size S2 between rows 22 of centers of laser beam ablation points 24.
• the step sizes S1 and S2 can be the equal or unequal.
• the starting point of each row 22 is not random as in prior art scanning methods. Instead, the center of each laser beam ablation point 25 on a particular row 22 is disposed linearly offset from a midpoint 27 defined between centers of two adjacent laser beam ablation points 28 and 30 of an adjacent row 32 of laser beam ablation points 24. The linear offset is normal to a line defining the adjacent row 32, forming an isosceles triangle between the ablation points 25, 28, and 30.
• the laser beam ablation points 24 of each layer 10 are evenly distributed in relation to the laser beam ablation points 24 of other ablated corneal layers, such that the center of no two laser beam ablation points 24 will center on an ablation point 24 the same location on the cornea. Even distribution of ablation points in the central area of the cornea is important, since visual acuity is affected greatly at this central area. Ninety degrees rotation of the rows 22 of laser beam ablation points is also permissible.
• FIG. 5 shows subsequent ablated layers A and B having ablation points 40 and 42, respectively.
• the ablation points 40, 42 on each ablated layer A, B, are located in accordance with the scanning method of the invention.
• the ablation points 42 of a subsequent ablation layer B are centered within the triangle T formed by adjacent ones of the ablation points 40 on the previous ablation layer A.
• the ablation points on an ablation layer ablated after ablation layer B are centered within the triangle shapes formed by adjacent ones of the ablation points 42 on ablation layer B.
• the locations of ablation points on subsequent layers are not randomized with respect to the previous layer, but instead are determined to provide an even distribution of power density not only with respect to each individual ablation layer, but also with respect to subsequent ablation layers. This even distribution of power density prevents the formation of corneal ridges.
• the laser beam ablation delivered by the scanning method of the invention results in generally evenly distributed laser beam ablation points.
• no ablation point on any particular layer is co-located with an ablation point on an adjacent ablation layer.
• FIG. 6 is an enlarged view of the overlap of ablation by a laser beam centered at adjacent ablation points delivered by the scanning method of the invention.
• the power density of overlapping laser beam ablation points is distributed more evenly than that of conventional scanning methods.
• each of the three laser beams 34, 36 and 38 of FIG. 6 supplement each other at perimeter areas 37 such that the ablation is more evenly distributed across the ablation area.
• the distribution of laser beam ablation points of each ablation layer is arranged depending on the total number of ablation layers, in order to evenly distribute the ablation points. In this way, the center point of no two ablation points on any ablation layer are co-located.
• a refractive laser system 50 provided in accordance with the present invention is shown which is capable of performing the scan and ablation defined above.
• the refractive laser system is shown which is capable of performing the scan and ablation defined above.
• a scanning device 120 capable of controllably changing the incident angle of the laser beam 110 passes the angled beam 110 to the focusing optics 140, onto a reflecting mirror 150 which adjusts an impinging angle of the laser beam 110 onto the target area
• the laser beam 110 preferably has an energy level less than 10 mJ/pulse.
• the target 160 is the cornea of an eye.
• An aiming system 170 has a visible wavelength light beam 180 (preferably from a laser diode or He-Ne laser) adjusted to be co-linear with the ablation laser beam 110 to aid adjustment of the normal incident angle.
• the basic laser head 200 is steered by a motorized stage for X and Y horizontal directions 210, and a motorized stage for the vertical (height) direction 220, which assures the focusing beam spot size and concentration of the beam onto the cornea.
• the laser head 200 may be of the stationary kind when the patient is disposed on a movable bed or chair.
• the refractive laser system 50 has a control panel 230 including a processor 250 for controlling the laser 100, for controlling scanning device 120, for controlling the angle of the beam 110, and for controlling all other aspects of the refractive laser system 50.
• Wheels 240 are provided to make the refractive laser system 50 portable.
• the basic laser head 200 and control panel 230 are of the type disclosed in U.S. Patent No. 5,520,679, the content of which is hereby incorporated by reference into the present specification.
• the processor 250 in the form of a microprocessor, digital signal processor, or microcontroller, includes in program memory 260 the procedures necessary to control the scanning device 120 to ensure that each laser beam ablation point 25 on a particular row 22 of laser beam ablation points 24 is disposed linearly offset from a midpoint 27 defined between two adjacent laser beam ablation points 28, 30 of an adjacent row 32 of laser beam ablation points 24 (FIG. 4), thereby defining the scanning technique of the invention.
• FIG. 4 the procedures necessary to control the scanning device 120 to ensure that each laser beam ablation point 25 on a particular row 22 of laser beam ablation points 24 is disposed linearly offset from a midpoint 27 defined between two adjacent laser beam ablation points 28, 30 of an adjacent row 32 of laser beam ablation points 24 (FIG. 4), thereby defining the scanning technique of the invention.
• the processor 250 controls the scanning device 120 by initially locating a first ablation point on a first row of ablation points at step 300.
• a second ablation point is located on the first row by stepping a distance S1 in the x and/or y-directions.
• the remaining ablation points on the first row are completed as indicated at step 315.
• a midpoint M between the first and second ablation points of the first row is determined.
• a second row of ablation points is located by stepping normal to the first row a distance S2. With the second row located, ablation points on the second row are located at points linearly offset from the midpoints of ablation points on an adjacent row, as indicated in step 340.
• the remaining ablation points on the second row are completed, as indicated in step 350, as are the ablation points for all remaining rows as indicated in step 360.
• a laser beam ablation point of one ablated layer can be controlled to not occur at the same location as a laser beam ablation point of any other ablated layer.
• the resulting ablated area is smoother than conventional ablated areas, and the power density of the laser beams is distributed more evenly than that of conventional techniques.

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• 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 Beam Processing (AREA)

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• 1998
  • 1998-12-01 WO PCT/US1998/025411 patent/WO1999027996A1/en not_active Application Discontinuation
  • 1998-12-01 EP EP98960566A patent/EP1056516A1/de not_active Withdrawn
  • 1998-12-01 AU AU16136/99A patent/AU1613699A/en not_active Abandoned

Non-Patent Citations (1)

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