Patent Application
20130226157
This invention is related to refractive eye surgery and especially to refractive eye surgery using an articulated mirror-lens relay arm to project a random scanning of one or more laser beams in the ablation of cornea tissue to reshape the cornea of the eye.
The cornea is a thin shell with nearly concentric anterior and posterior surfaces and a central thickness of about 520 micrometers. It has an index of refractive of 1.377 and a nominal radius of curvature of 7.86 mm. The epithelium, forming the anterior surface of the cornea, is about 70 micrometers thick in young people at the center. Underlying the epithelium is a layer called Bowman's layer or Bowman's membrane, which is about 12 micrometers thick. This covers the anterior surface of the stroma, which makes up the bulk of the cornea and consists primarily of collagen fibers. The endothelium that forms the posterior layer of the cornea is a single layer of cells.
About three-quarter of the refractive power of the eye is determined by the curvature of the anterior surface of the cornea, so that changing the shape of the cornea offers a way to significantly reduce or eliminate refractive errors of the eye. The stroma is thick enough so that portions of its anterior region can be ablated away to change its profile and thus change the refractive power of the eye for corrective purposes, while leaving plenty of remaining stroma tissue.
Various lasers have been used for ophthalmic applications including the treatment of glaucoma, cataract and refractive surgery. For refractive surgeries (or corneal reshaping), ultraviolet (UV) lasers, such as excimer lasers at 193 nm and fifth-harmonic Nd:YAG at 213 nm have been used for large area surface corneal ablation in a process called photorefractive keratectomy (PRK) and for large area stroma ablation in a process called laser assisted in situ keratomileusis (LASIK). Corneal reshaping may also be performed by laser thermal coagulation currently conducted with Ho:YAG laser using a fiber-coupled contact and flying laser spots non-contact type process.
Refractive surgery has reached a new dimension due to the development of the excimer laser (193 nm) and fifth harmonic solid state laser (190 nm-215 nm) being used to photo ablate the corneal tissue to reshape the cornea. In my prior U.S. Pat. No. 5,480,396 dated Jan. 2, 1996 for LASER BEAM OPHTHALMOLOGICAL SURGERY METHOD AND APPARATUS and U.S. Pat. No. 5,599,340 dated Feb. 4, 1997 for LASER BEAM OPHTHALMOLOGICAL SURGERY METHOD AND APPARATUS, single or plural beams are formed by splitting one laser beam, and uses a random scanning pattern of the beams to scan the laser beams over the cornea. Most of the latest refractive laser systems have used either one or two laser beams and a random scanning pattern.
However, all the refractive laser systems available in the market are similar in that they require the patient eye to align with the laser beam. In this case, the laser cabinet is bulky and one laser delivery arm is used to transfer the laser beam into a random scanning pattern on the cornea. The laser delivery arm is around one meter and the laser beam is turned down under the microscope in order to align the laser beam with the microscope's visual axis. The distance from the lower part of the laser delivery arm to the surface of the cornea is around 250 millimeters. The patient is lying down on a patient table that can be XYZ fine tuned in order to move the surface of the cornea until it reaches the focusing point of the microscope and laser delivery set up. In this kind of laser system organization, the patient is required to move constantly in order to align the patient eye to the laser beam. To prevent eye movement during the surgery, the surgeon uses a ring or other tool to stabilize the eye ball. Most of the modern laser systems employ an eye tracker system to track the eye movement but even a very complicated three dimensional eye tracking system cannot guide the laser beam to be normal incidence upon the corneal surface if the eye ball rotates.
U.S. Pat. No. 5,599,340 has a UV laser with an XY scanned device located in a fixed delivery arm that delivers the laser beam to the cornea without any mechanical contact. The visual axis of a microscope is aligned with the UV laser beam since the microscope is used to monitor the ablation. A sophisticated movement patient table is used to move the patient's eye into alignment with the visual axis of the microscope and the UV laser beam. This requires significant effort for the surgeon to precisely align the beam with the eye. My U.S. patent application Ser. No. 13/373,591 uses a femtosecond laser where the laser beam pulses are sent through an XY-scanning device located in a main cabinet. The beam then travels through a mirror-lens relay optical arm to a hand piece, that contains an XYZ piezo stage and a very short focal length lens with a high numerical aperture, and is connected to the surface of the eye via a suction ring. This apparatus therefore aligns the laser beam with the eye to simplify the surgical procedure by removing the necessity and effort of the surgeon and patient of using a sophisticated movement patient table to align the eye with the laser beam. However, a millimeter sized laser spot and a 10 mm ablation area is required for UV laser refractive surgery so that a highly focused lens is not suitable for this application. In the UV laser application, the femtosecond laser's XYZ piezo stage is no longer required when using a long focal length scan, focusing lens with a low numerical aperture to cover the 10 mm ablation area.
The present invention proposes a design for a laser system in which the laser beam aligns with the patient eye rather than having the patient's eye aligned to the UV laser beam. The laser system uses a mirror-lens relay optical arm to transfer a random scanning pattern after XY galvanometer to a remote position that is around 1.5 meters away from the scanner device and with the same characteristics of the scanned laser beams. The laser beam then passes into the scan, focusing lens of the hand piece and is directed to the patient's eye.
In greater detail, the hand piece consists of two sections: the scan lens section and the viewing/centering section. The scan-lens section, attached to the far end of the mirror-lens relay optical arm, contains a high F-number (low NA) F-Theta scan, focusing lens with a focusing length of around 100 mm that allows the focusing point of the scanned laser beam to pass into the viewing/centering section of the hand piece. The scan lens also converts a divergent beam into a parallel beam which has an advantage on the ablation efficiency curve on the corneal surface. The viewing section of the hand piece includes a turn down mirror which has a working distance of approximately 50 mm from the lower surface of the hand piece to the eye surface and is arranged in such a way that it can be in contact with and stabilize the eye by using the eye stabilization and distance control unit. A power detector is attached to the viewing section to monitor the power level of the laser beam. The viewing section also contains four centering lights used to aid in properly centering the laser beam onto the cornea. Suction for debris removal is located in the eye stabilization and distance control unit to remove the laser ablation tissue particles through tiny ventilation holes. In this laser delivery configuration, the laser beam is directed by the surgeon to the eye so there is no need to move the patient during the surgery. Since the hand piece with eye stabilization and distance control unit is placed by the surgeon on the top of the eye to align the laser beam with the eye, there is no need to use an eye tracker to detect eye movement. In the new system, even if the eye is moving during the surgery, the laser beam remains normal incidence on the eye, which the eye tracker system cannot accomplish in existing systems.
This invention is related to refractive eye surgery and especially to refractive eye surgery using an articulated mirror-lens relay arm to project a random scanning of one or more laser beams to ablate cornea tissue to reshape the cornea of the eye. A method of ablating eye tissue includes generating a UV laser beam, such as with an excimer laser, and directing the generated laser beam through a manually activated shutter and through a homogenizer and onto a galvanometer xy-scanner. The scanner generates an overlapping random pattern laser beam signal. A selected hand piece has a scan, focusing lens therein and an eye stabilization and distance control member extending therefrom, which eye stabilization and distance control member has an open center area and an eye contact edge thereon. The selected hand piece also has at least one aligning light thereon for aligning the eye stabilization and distance control member with a patient's eye and may have a video camera attached thereto. The generated laser beam random pattern is directed through an articulated mirror-lens relay arm to the hand piece scan lens mounted in the hand piece and through the open center of the eye stabilization and distance control member. The hand piece is manipulated on the end of the articulated mirror-lens relay arm to align the eye stabilization and distance control unit on a patient's eye and then is further manipulated to bring the eye stabilization and distance control member eye contact edge into eye contact with a patient's eye. The random pattern laser beam from the laser scanner is then impinged onto the surface of the patient's eye responsive to activation of the shutter to ablate tissue from the surface of the patient's eye. Thus, surgical ablation is performed on a patient's eye with a random overlapping laser beam through a hand manipulated hand piece in contact with the patient's eye.
A laser ophthalmological surgery apparatus has a UV laser, such as an excimer laser, for generating a UV laser beam which beam is applied to a control shutter and through a homogenizer and into a galvanometer xy-scanner. The scanner produces a predetermined random overlapping scanning pattern. A computer generates the random scanning pattern signal for controlling the scanner to produce the random overlapping scanning pattern from the input laser beam. A hand piece has a focusing lens therein and an eye stabilization and distance control member attached to and extending therefrom. The eye stabilization and distance control member has an open center area and an eye contact edge. One or more, but typically four, alignment lights are mounted on the hand piece for aligning the eye stabilization and distance control member on a patient's eye.
An articulated mirror-lens relay arm has a hand piece attached to one end thereof and the other end positioned for receiving the scanned laser beam and directing the laser beam to the hand piece and through an open center area of the eye stabilization and distance control member. The hand piece can be manipulated to position it to direct the laser beam onto a patient's eye by manipulating the articulated mirror-lens relay arm to position the eye stabilization and distance control member eye contact edge into contact with a patient's eye to stabilize a patient's eye for ablating tissue therefrom in a random overlapping pattern with the laser beam. A vacuum pump has a vacuum line connected to the hand piece to remove the eye's ablated tissue. Surgical ablation can thus be performed on a patient's eye with a random overlapping laser beam through a hand manipulated hand piece in contact with the patient's eye.
The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the description, serve to explain the principles of the invention.
In the drawings:
A method of ablating eye tissue, as illustrated in
The ophthalmological apparatus has a main cabinet 15 and a hand piece 16 connected thereto with the articulated mirror-lens relay arm 12. The excimer laser 10 is positioned in the main cabinet 15 and has a laser beam output of laser pulses. A laser beam homogenizer 17 is positioned to homogenize the laser beam to smooth out irregularities in the laser beam before scanning the laser beam into an overlapping random scanning pattern of laser pulses. The scan lens 13 is located in the hand piece 16 to receive the overlapping random scanning pattern of laser pulses from the laser scanner 11 which are centered on the center axis of the focusing lens 13. The scan, focusing lens 13 is positioned to focus the predetermined overlapping random scanning pattern of laser pulses onto a turn down lens 18 and onto a patient's eye 14 to ablate a predetermined sub-area of eye tissue. Thus, a patient's eye has a predetermined area thereon ablated by overlapping random scanning pattern of laser pulses.
The laser ophthalmological surgery apparatus in accordance with the present invention as seen in the drawings includes a user interface connected to a main cabinet 15 in
Following the light path in greater detail, the light pulse generator is an excimer laser 10 (wavelength 193 nm) or fifth harmonic generated solid state laser (wavelength is from 193 nm to 213 nm) with a pulse width less than 20 nanosecond and a pulse repetition rate from 100 Hz to several thousand Hz. The laser beam is blocked by the shutter 19 until the foot switch 37 is depressed thereby activating a switch. While the foot switch 37 is pressed, the laser beam is allowed to continue to the homogenizer 17 where the laser beam spot size is homogenized, i.e. smooths out the irregularities in the laser beam. The beam continues to the XY-galvanometer 11 where it is deflected to create an overlapping random scanning pattern 20, as shown in
Inside the hand piece 16, a compact scan, focusing lens 13 is used to reduce the spot size of the laser beam spots to less than 1 mm and the size of the overlapping random scanning pattern 20 to a diameter of less than 10 mm. The turn-down mirror 18 directs the laser beam towards the eye while a power meter 28 detects the laser beam's power.
The hand piece 16 is attached to the eye 14 with a disposable eye stabilization and distance control unit 31 with the eye contact edge 32 contacting the eye. The ablated tissue particles are removed through suction vents 29 by the vacuum pump 34 having a line in the eye stabilization and distance control unit 31 via a debris suction tube 38 that is attached to the eye stabilization and distance control unit vacuum vents 29. The eye stabilization and distance control unit 31 is placed on the eye 14 to correctly level the laser beam focusing point and to stabilize eye movement. The eye itself has some minor movement during the surgery, however, the laser beam is always maintained at a normal incidence to the eye since the hand piece has the same movement as the eye movement. Centering lights 30 are used to delineate the target area. A small cam mirror 40 directs the view of the eye with the centering lights to a video camera 41 so that the system's computer 13 can receive the video signal to detect the pupil location to provide feedback during the centering procedure.
The ablation patterns generated by this laser apparatus include but are not limited to predetermined myopia, hyperopia and astigmatism patterns. The computer randomly rearranges the ordered ablation data into a new random sequence of ablation. The laser beam spots are delivered to cornea in overlapping random patterns.
The process for refractive eye surgery uses the apparatus described having an articulated mirror-lens relay arm to project a random scanning of one or more UV laser beams to ablate cornea tissue to reshape the cornea of the eye. The method includes ablating eye tissue by generating a UV laser beam, such as with an excimer laser 10, and directing the generated laser beam through a manually activated shutter 19 and through a homogenizer 17 and onto a galvanometer xy-scanner 11. The scanner generates an overlapping random pattern laser beam signal. A selected hand piece 16 has a focusing lens 13 therein and an eye stabilization and distance control member 31 extending therefrom, which eye stabilization and distance control member has an open center area and an eye contact edge 32 thereon. The selected hand piece 16 also has at least one aligning light 30 thereon for aligning the eye stabilization and distance control member 31 with a patient's eye and may have a video camera 41 attached thereto. The generated laser beam random pattern is directed through an articulated mirror-lens relay arm 12 to the hand piece scan lens 13 mounted in the hand piece and through the open center of the eye stabilization and distance control member 31. The hand piece 16 is manipulated on the end of the articulated mirror-lens relay arm 12 to align the eye stabilization and distance control unit 31 on a patient's eye 14 and then is further manipulated to bring the eye stabilization and distance control member eye contact edge 32 into eye contact with a patient's eye 14. The random pattern laser beam from the laser scanner 11 is then impinged onto the surface of the patient's eye responsive to activation of the shutter 19 to ablate tissue from the surface of the patient's eye. Thus, surgical ablation is performed on a patient's eye 14 with a random overlapping laser beam through a hand manipulated hand piece 16 in contact with the patient's eye.
It should be clear at this time that a process and an apparatus for performing refractive eye surgery by surgical ablation on a patient's eye has been shown which uses a random overlapping laser beam through a hand manipulated hand piece in contact with the patient's eye. However the present invention is not to be considered limited to the forms shown which is to be considered illustrative rather than restrictive.
