CA2207320A1

CA2207320A1 - Laser beam ophthalmological surgery method and apparatus

Info

Publication number: CA2207320A1
Application number: CA002207320A
Authority: CA
Inventors: Gabriel Simon; Cheng-Hao Huang
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-12-09
Filing date: 1995-11-13
Publication date: 1996-06-13
Also published as: AU689353B2; US5480396A; DE69520074D1; AU4159196A; DE69520074T2; WO1996017555A1; EP0798987A4; JPH10510177A; KR100396392B1; EP0798987A1; EP0798987B1; TW319693B

Abstract

A laser beam ophthalmological surgery method includes the steps of generating a laser beam (12) and splitting the generated laser beam (12) into multiple laser beams (14, 15) which are simultaneously focused onto a plurality of scanners (16, 21, 45, 46, 48, 50). Each scanner (16, 21, 45, 46, 48, 50) in turn produces a predetermined scanning pattern focused on the cornea (20) of a patient's eye (24) to ablate the cornea tissue and with at least two beams (25, 26) simultaneously scanning and ablating the cornea tissue. Scanning is controlled from a central processing unit (27) to perform the surgical procedure, removing a laser thickness of the cornear tissue to provide a safer and more predictable surgical procedure in the reshaping of the cornea. A
laser ophthalmological surgery apparatus (10) is provided which includes a laser (11) generating a laser beam (12), a beam splitter (13, 44) for splitting the laser beam (12) into a plurality of laser beams (14, 15), and a plurality of scanners (16, 21, 45, 46, 48, 50), each positioned for receiving one of the laser beams from the beam splitter (13, 44) and producing a predetermined scanning pattern from the laser beam (12) and impinging the scanning pattern upon the cornea (20) of a patient's eye (24).

Description

WO96/17555 PCT~S95/14819 LASER BEAM OPHTHALMOLOGICAL SURGERY
M~L~OV AND APPARATUS

BACKGROUND OF THE INVENTION

3 This invention relates to refractive eye surgery 4 and especially to refractive eye surgery using a plurality of laser beams in the ablation of cornea 6 tissue to reshape the cornea of a person's or animal's 7 eye.
8 The cornea is a thin shell with nearly concentric 9 anterior and posterior surfaces and a central thickness of about 520 micrometers. It has an index 11 of refraction of 1.377 and a nominal radius of 12 curvature of 7.86 mm. The epithelium, forming the 13 anterior surface of the cornea, is about 70 14 micrometers thick in young people at the center.
Underlying the epithelium is a layer called Bowman's 16 layer or Bowman's membrane, which is about 12 17 micrometers thick. This covers the anterior surface 18 of the stroma, which makes up the bulk of the cornea 19 and consists primarily of collagen fibers. The endothelium forms the posterior layer of the cornea 21 and is a single layer of cells.
22 About three-quarters of the refractive power of 23 the eye is determined by the curvature of the anterior 24 surface of the cornea, so that changing the shape of the cornea offers a way to significantly reduce or 26 eliminate a refractive error of the eye. The stroma 27 is thick enough so that portions of its anterior 28 region can be ablated away to change its profile and 29 thus change the refractive power of the eye for W O 96/17555 PCTrUS95/14819 1 corrective purposes, while leaving plenty of remaining 2 stroma tissue.

3 Various lasers have been used for ophthalmic 4 applications including the treatments of glaucoma, cataract and refractive surgery. For refractive 6 surgeries (or corneal reshaping), ultraviolet (W) 7 lasers (excimer at 193 nm and fifth-harmonic of Nd:YAG
8 at 213 nm) have been used for large area surface 9 corneal ablation in a process called photorefractive keratectomy (PRK). Corneal reshaping may also be 11 performed by laser thermal coagulation currently 12 conducted with Ho:YAG lasers using a fiber-coupled, 13 contact and non-contact type process.
14 Refractive surgery has reached a new dimension due to the development of the excimer laser (193nm) 16 and fifth harmonic of solid state laser (19Onm-215nm) 17 being used to photoablate the cornea tissue to reshape 18 the cornea. Several approaches have been proposed to 19 deliver the laser beams to the surface of the cornea including using a mask or diaphragm and move the mask 21 or diaphragm to block the laser beam to achieve a 22 desired curvature on the outer surface of the cornea.
23 It has also been proposed to use a scanner to move a 24 laser beam spot on the outer surface of the cornea to ablate the tissue to change the curvature on the 26 cornea. Combining the mask or diaphragm and scanner 27 to block and move a laser beam is also used to achieve 28 a desired curvature on the outer surface of the 29 cornea. The mask or diaphragm approach requires a high energy laser and a rough or stepped cornea 31 surface is generated in the laser interacting with the 32 cornea. When the laser interacts with the corneal 33 tissue, it generates some water that remains on the 34 surface of the cornea (like sweat water). This 096/17555 PCT~S95/14819 1 changes the ablation rate when a new laser pulse 2 reaches the cornea. If this is not taken into 3 consideration, an irregular pattern can be induced 4 called an "island". Central corneal islands have been described in connection with prior laser beam delivery 6 systems. The scanning or combination of mask and 7 scanner approach produces a smoother cornea surface 8 but nonsymmetrical beam profiles and the sweat water 9 effect creates an island effect which is caused by a nonsymmetrical ablation on each side or point of the 11 corneal surface. The present invention uses two or 12 more laser beams which multiple laser beams are split 13 from one laser source with an out of phase 14 relationship. The spatial energy distribution mode is scanned on the cornea or in the cornea simultaneously 16 by using two or more scanning devices controlled by a 17 predetermined program in a computer controller.
18 Because the symmetrical laser beams are located and 19 moved on the cornea, the cornea will compensate for the uneven situation of the sweat water effect when 21 the laser interact with the cornea tissue and non-22 symmetrical laser beam spatial energy distribution.
23 Refractive error can be divided in two 24 categories. Spherical and cylindrical. Spherical can effect the eye as myopic or hyperopic. Cylindrical 26 can effect the eye as myopic or hyperopic astigmatism.
27 The present invention uses a computer program to avoid 28 ablation of the central part of the cornea in the 29 hyperopic astigmatism and thus results in a safer, more predictable, and faster surgery procedure.
31 In the case of hyperopic combined with 32 astigmatism of any cornea, the center is never 33 touched.

W 096/17555 PCT~US95/14819 1 SU~ RY OF THE INV~N11ON
3 A laser beam ophthalmological surgery method 4 includes the steps of generating a laser beam and splitting the generated laser beam into a plurality of 6 laser beams which are simultaneously focused onto a 7 plurality of scanners. Each scanner produces a 8 predetermined laser beam scanning pattern and is 9 directed onto the cornea of a patient's eye to ablate the cornea tissue and with at least two scanning beams 11 simultaneously ablating the cornea tissue. Scanning 12 is controlled from a central processing unit to 13 perform the surgical procedure. A laser 14 ophthalmological surgery apparatus is provided which includes a laser generating a laser beam, a beam 16 splitter for splitting the laser beam into a plurality 17 of laser beams. A plurality of scanners are each 18 positioned for receiving one of the laser beams from 19 the beam splitter and producing a predetermined scanning pattern from the laser beam and impinging the 21 scanning pattern upon the cornea of a patient's eye.
22 The apparatus also includes focusing optics for 23 focusing each laser beam and optics for directing the 24 scanned beams onto the cornea in a predetermined scanning pattern for ablating a portion of the cornea 26 of the eye. A computer connected to each scanner 27 produces the desired scanning pattern which may be 28 either a concentrical circular symmetrical pattern or 29 a linear parallel symmetrical beam pattern.

= -- --5 PCT~S95114819 3 Other objects, features, and advantages of the 4 present invention will be apparent from the written description and the drawings in which:

6 Figure 1 is a block diagram of a dual laser beam 7 cornea ablation system;

9 Figure 2 is a schematic diagram of the optics for a dual laser beam cornea ablation system;
11 Figure 3 is a scan pattern using the apparatus of 12 Figures 1 and 2;
13 Figure 4 is a second scan pattern which can be 14 performed with the apparatus of Figures 1 and 2;
Figure 5 is a diagrammatic scan pattern similar 16 to Figure 4 with a pair of laser beams sc~nn;ng in a 17 circular path and in the same direction of rotation;
18 Figure 6 is a cross-sectional view illustrating 19 sculptured surface curvatures on both 90~ and 180~ for correcting hyperopic astigmatism;
21 Figure 7 illustrates one pattern for correction 22 of cornea astigmatism correction; and 23 Figure 8 is another pattern for correction of 24 cornea astigmatic correction.

28 Referring to the drawings and especially to 29 Figure 1, a block diagram of a dual laser beam cornea ablation system 10 is shown having a laser 11 which 31 can be an excimer laser producing a laser beam 12 32 having an ultraviolet wavelength of 193 nm. The laser 33 beam 12 is impinged upon a beam splitter 13 which 34 divides the beam 12 into two laser beams 14 and 15.

CA 02207320 l997-06-06 W O96/17555 PCTrUS9S/14819 1 Laser beam 14 is then impinged upon a galvanometer 2 scanner 16 which is a typical scanner using a 3 galvanometer having a mirror attached thereto in which 4 the galvanometer produces a motion to thereby move the mirror having the beam 14 impinged thereupon to scan 6 the beam. The scanning beam 17 iS directed with 7 mirrors 18 or other optics to apply the beam to a 8 patient's cornea 20. The beam 15 is applied to a 9 second scanner 21 producing a scanned beam 22 onto a mirror or other beam directing optics 23 onto the 11 cornea 20 of a patient's eye 24. The beams 17 and 22, 12 as directed by the optics 18 and 23, produce parallel 13 laser beams 25 and 26 which simultaneously impinge 14 upon the cornea 20 of the eye 24 and have a controlled pattern in accordance with the scanners 16 and 21.
16 In the present invention, a microcomputer 27 iS
17 connected to the laser 11 through the synchronization 18 and every central circuit 19 and can be programmed to 19 produce any type of scanning pattern desired and is 20 connected to an X,Y coordinate scan driver 2 8 through 21 the line 30 which produces X,Y coordinate scan driver 22 signals in the lines 31 and 32 connected to the 23 scanner 16 so that electrical signals from the X,Y
24 coordinate scan driver 28 drive the scanner 16 in an 25 X,Y coordinate pattern. The computer 27 puts out 26 identical X,Y coordinate scan signals to the X,Y
27 coordinate scan driver 33 through the connection 29 28 which in turn puts out X,Y coordinate signals in the 29 lines 34 and 35 which are connected to the scanner 21 30 to produce an X,Y coordinate scanning pattern in the 31 scanner 21. The scanning beams 25 and 26 impinging 32 upon the eye in the case of an excimer laser has a 33 beam wavelength of 193 nm but each beam may have an 34 out of phase relationship with each other beam on the WO96/175S5 PCT~S95/14819 1 spatial energy distribution mode by using the 2 transmittance and reflective characteristics of the - 3 beam splitter 13.
4 The use of two or more scanning devices sc~nn;ng two or more laser beams on the outer surface o~ the 6 cornea is used to ablate the eye simultaneously with 7 each beam. This can be accomplished in the patterns 8 as shown in Figure 3 in which the circle 36 indicates 9 the cornea of the eye and the scan line 37 scanning in one direction is performed by one of the scanning 11 laser beams 25 or 26 while the scanner 38 scans 12 simultaneously in the opposite direction to the 13 scanning beam 37 with both beams scanning 14 simultaneously and superimposed trace. However as can be seen, the sc~nning lines are numbered la-ld and 16 going in the opposite direction from the scans 2a-2d 17 to indicate that, in the case of two laser beams 25, 18 scanning line 37 is scanning in one direction while 19 the laser beam 26 scans the lines 38 from the opposite side and in the opposite direction from the laser beam 21 scan lines 37. Similarly as shown in Figure 4, the 22 cornea 36 is scanned in a circular fashion with a scan 23 line 40 going in one direction while the laser beam 26 24 is scanned superimposed thereto along scan lines 41 from the opposite side of the eye 36 with both beams 26 scanning simultaneously. Beam 26 is shown scanning 27 with the dashed lines while solid lines are indicating 28 the scanning of beam 25.
29 Referring more specifically to Figure 2 of the drawings, the laser 11 which, again may be an excimer 31 laser producing an ultraviolet output beam 12, is 32 applied to a shutter 42 which in turn applies the 33 laser beam to a focusing lens 43. The focusing lens 34 focuses the beam 12 upon a beam splitter 44. The CA 02207320 l997-06-06 W O96/17555 PCTrUS95/14819 1 focusing lens 43 and beam splitter 44 are part of the 2 focusing and beam splitter 13 of Figure 1 and produce 3 the split beams 14 and 15. It will, of course, be 4 clear that the beam could be split into more than two beams as desired without departing from the spirit and 6 scope of the invention. The beam 14 is then applied 7 to the scanning pair 16 of Figure 1 which has a first 8 scanner 45 scanning the beam and applying the scanned 9 beam to a second scanner 46. Both scanners 45 and 46 are galvanometer scanners having electrical 11 galvanometers having mirrors attached thereto so that 12 the scanner 45 can scan the beam in a Y direction 13 while the scanner 46 can scan the beam in an X
14 direction to give an X,Y control of the beam 17 being impinged upon the mirror 18 to form the scanning beam 16 25 onto the eye 24 cornea 20. The scanner 45 has a Y
17 coordinate signal applied thereto through the line 34 18 while the scanner 46 has a line applied thereto 19 through the X coordinate line 35, which signals are 20 produced in the X,Y coordinate scan driver 33 which 21 receives the control signals through the line 29 from 22 the central processing unit 27. The computer 27 has 23 a control screen 47 mounted thereto and also produces 24 the X,Y coordinate control signals over the connection 25 30 to the X,Y coordinate scan driver 28 producing the 26 Y coordinate signal through the connection 32 and the 27 X coordinate signals through the connection 31 to a 28 pair of scanners 48 and 50 which each produces one 29 coordinate scanning signal which produces a scanning 30 beam 22 controlled with optics 23 to form the eye 31 scanning beam 26 onto the surface of the eye 24.
32 It should be clear at this time, that an 33 apparatus has been provided for producing a plurality 34 of laser beams which are simultaneously scanned over WO96/17555 PCT~S95/14819 1 the surface of the cornea of the eye to ablate a 2 portion of the eye for refractive correction to the 3 cornea and which beams are produced simultaneously on 4 opposite sides of a portion of the cornea and away from the center of the cornea for doing a controlled 6 scan ablation of the cornea.
7 The method of performing laser beam 8 ophthalmological surgery includes the step of 9 generating a laser beam from a laser, then splitting the laser beam through a beam splitter 13 into a 11 plurality of laser beams and then applying each split 12 laser beam to an X,Y scanner or a pair of scanners 13 which control the beam which scan beam is then applied 14 through mirrors or optics onto the surface of the eye for performing the ablation of a portion of the cornea 16 of the eye. Multiple scanning beams are scanned 17 simultaneously and directed generally superimposed to 18 each other in accordance with a computer program 19 controlling the X,Y coordinate scanners controlling each of the pair of beam scanners for each of the 21 laser beams. The process includes focusing the beams 22 upon the beam splitter as well as directing the 23 plurality of scanning laser beams onto the surface of 24 the eye and in the controlling of the beams for predetermined patterns, such as illustrated in Figures 26 3 and 4.
27 Figure 6 illustrates a typical cross-sectional 28 view of a sculptured surface curvature of an eye on 29 both 90~ and 180~ achieved with computer control for the hyperopic astigmatic correction while Figures 7 31 and 8 are algorithms of an ablated cornea for 32 astigmatic correction, which corrections are performed ~ 33 in accordance with the present apparatus through the 34 computer control of the computer 26.

CA 02207320 l997-06-06 W 096tl7555 PCTtUS95114819 1 In operation, the present multiple laser beam 2 delivery system provides for the operator to make two 3 computer selections. One selection is for myopic, 4 hyperopic or astigmatism corrections which determines the dual beam scanners scanning pattern. Information 6 is fed to the computer for issuing the necessary 7 signals. The computer also has an input for the 8 amount of dioptic correction for a particular 9 patient's eye. The computer then puts out signals based on an algorithm for either myopic, hyperopic or 11 astigmatism correction and for the dioptics of 12 correction necessary for a particular patient's eye.
13 The feedback signals from the scanner also allows the 14 computer to make corrections in the driving of the multiple scanner pairs to manipulate the multiple 16 laser beam simultaneously. Thus, the computer 17 produces a scan to ablate the cornea with a pair of 18 laser beams in accordance with the algorithm shown in 19 Figures 7 and 8 for a hyperopic astigmatic correction with the amount of correction being determined by the 21 diopter input.
22 It should be clear at this time, that the present 23 invention is directed to both a method and an 24 apparatus for use in ophthalmological surgery on the 25 outer surface of the cornea or in the cornea to reduce 26 astigmatism or myopic or hyperopic correction or 27 combinations of myopic and astigmatisms or 28 combinations of hyperopic and astigmatism corrections 29 by using two or more laser beams simultaneously with 30 the multiple laser beams formed from beam splitters 31 from the same laser source with an out of phase 32 relationship with each beam obtained through the beam 33 splitter and which beams are scanned on predetermined 34 computer controlled laser scanners to perform W096/17555 PCT~S95/14819 1 refractive surgery on a patient's eye. The ablation 2 with a plurality of laser beams in accordance with the =3 present invention produces a refractive correction in 4 the eye symmetrically ablating the central part of the cornea tissue when correcting hyperopic astigmatism, 6 thus resulting in a safer and more predictable 7 surgical procedure to correct hyperopic astigmatism.
8 However, the present invention 9 should not be construed as limited to the forms shown which are to be considered illustrative rather than 11 restrictive.

Claims

CLAIMS:

We claim:

1. A laser beam ophthalmological surgery method for ablating a portion of a cornea comprising the steps of:
generating a laser beam ( 12);
splitting the generated laser beam (12) into a plurality of laser beams ( 14, 15);
focusing each of said plurality of laser beams (14, 15) onto a scanner (16, 21, 45, 46, 48, 50);
scanning each of said plurality of laser beams (14, 15) in a predetermined scanning pattern for ablation of the cornea (20) of a patient's eye (24);
directing said plurality of scanning laser beams (25, 26) parallel to each other directly onto the surface of the cornea (20) of an eye of a patient with said plurality of scanning beams (25, 26) scanning a generally superimposed parallel pattern to each other; and controlling each said scanner (16, 21, 45, 46, 48, 50) from a central processing unit (27) to thereby surgically reshape the cornea of the eye.

2. A laser beam ophthalmological surgery method in accordance with claim 1 in which the step of scanning a plurality of laser beams ( 14, 15) includes scanning each of two laser beams, each laser beam being out of phase with the other laser beam.

3. A laser beam ophthalmological surgery method in accordance with claim 2 in which the step of splitting the generated laser beam into a plurality of laser beams includes splitting the laser beam into two laser beams (14, 15) and impinging each laser beam onto a separate scanner (16, 21, 45, 46, 48, 50).

4. A laser beam ophthalmological surgery method in accordance with claim 3 in which each scanning laser beam is scanning a generally parallel and spaced beam (25, 26) from the other laser beam (25, 26) with each parallel beam forming a superimposing pattern with a second parallel beam.

5. A laser beam ophthalmological surgery method in accordance with claim 4 in which the step of controlling said scanning includes controlling two scanners (16, 21, 45, 46, 48, 50) with the same central processing unit (27).

6. A laser beam ophthalmological surgery method in accordance with claim 5 in which the step of generating a laser beam includes generating a laser beam (12) having a ultra-violet wavelength between 193nm and 215nm.

7. A laser beam ophthalmological surgery method in accordance with claim 6 in which the step of generating a laser beam (12) includes generating a laser beam from an excimer laser having a wavelength of 193nm.

8. A laser beam ophthalmological surgery method in accordance with claim 5 in which the step of scanning each of said laser beam includes scanning each laser beam with a pair of galvanometer scanners (16, 21, 45, 46, 48, 50).

9. A laser beam ophthalmological surgery method in accordance with claim 8 in which the step of scanning each of said pair of scanning beams includes scanning each of said laser beams (14, 15) of the two beams in a plurality of generally straight lines, each parallel to the other and each beam traveling in an opposite direction from the other.

10. A laser beam ophthalmological surgery method in accordance with claim 9 in which the step of scanning a pair of laser beams includes scanning each of said laser beams (14, 15) of the two laser beams parallel to each other in a generally circular beam pattern (Figures 4 and 5) around the central portion of the cornea.

11. A laser ophthalmological surgery apparatus (10) for abalating a portion of a cornea comprising:
a laser (11) for generating a laser beam (12);
a beam splitter (13, 44) for splitting the laser beam (12) from said laser (11) into a plurality of laser beams (14, 15);
a plurality of scanners (16, 21, 45, 46, 48, 50), each positioned for receiving one of said laser beams (14, 15) from said beam splitter (13, 44) and producing a predetermined scanning pattern from the laser beam (14, 15) impinging thereupon;
focusing optics (43) positioned between said laser (11) and said beam splitter (44) for focusing each of said laser beams onto one said scanner;
directing means (23, 18) positioned between said plurality of scanners (16, 21, 45, 46, 48, 50) and said cornea for directing each of said laser beams onto the cornea of a patient's eye simultaneously in a parallel pattern for ablating a portion of the cornea of the eye; and a computer (27) connected to each said scanner for controlling each said scanner (16, 21, 45, 46, 48, 50) in a predetermined pattern whereby a plurality of laser beams can perform a surgical procedure on a patient's eye.

12. A laser beam ophthalmological surgery apparatus (10) in accordance with claim 11 in which said beam splitter produces a plurality of out of phase laser beams.

13. A laser beam ophthalmological surgery apparatus (10) in accordance with claim 12 in which said beam splitter (13, 44) splits the generated laser beam into two out of phase laser beams and each laser beam impinged onto a separate beam scanner (16, 21, 45, 46, 48, 50).

14. A laser beam ophthalmological surgery apparatus (10) in accordance with claim 13 in which said directing means (18, 23) directs each scanning laser beam generally parallel and spaced from each other onto a patient's eye.

15. A laser beam ophthalmological surgery apparatus (10) in accordance with claim 14 in which said computer (27) controls each of said beam scanners (16, 21, 45, 46, 48, 50) simultaneously.

16. A laser beam ophthalmological surgery apparatus (10) in accordance with claim 15 in which said laser (11) generates a laser beam (12) having an ultra-violet wavelength between 193nm and 215nm.

17. A laser beam ophthalmological surgery apparatus (10) in accordance with claim 16 in which said laser (11) is an eximer laser having a wavelength of 193nm.

18. A laser beam ophthalmological surgery apparatus (10) in accordance with claim 17 in which each said scanner (16, 21, 45, 46, 48, 50) is a galvanometer scanner having a mirror mounted to galvanometer.