MXPA99003720A - Method and device for sculpturing laser beams - Google Patents

Abstract

This invention is a method for sculpturing a laser beam (13) in a predetermined pattern using a device (17) between the laser source (11) and the target (23). The method comprises a series of sequential steps in which at least two regions of the cornea (177) are each exposed to increasingly larger portions of the laser beam (13). In the preferred embodiment, two pairs of complimentary regions of the cornea (177) will be sequentially exposed to laser radiation. In each such region, a first part will be exposed to a substantially segmental portion of the beam (13), and then at least another larger substantially segmental portion of the beam (13) in which the larger segmental portion, includes the smaller segmental portion. In the preferred embodiment, the target (23) is the human eye, and the predetermined pattern is intended to shape the eye to treat it for astigmatism, myopia, or hyperopia.

Description

METHOD AND DEVICE FOR MODELING LASER RAYS FIELD OF THE INVENTION The present invention relates to systems, methods and devices for modeling a laser beam. More particularly, the invention relates to a device located in the path of a laser for blocking or hiding a portion of the laser beam according to a predetermined pattern wherein the portion of the laser beam reaching the target can be varied, and to methods for use such a device. The use of lasers to alter the surface of objects is becoming more important as it becomes apparent that lasers can be precisely focused and the amount of energy transferred to the target can be controlled closely. Lasers have been used in eye surgery, for example, to treat the retina of diabetic people. Lasers have also been used by doctors for other precise and delicate eye surgeries. In all eye surgery procedures of the prior art, as well as in other efforts to use laser beam pulses to act on or burn tissue or other matter, a great concern occurs in relation to the ability to control the size and intensity of the laser. Thunderbolt. In addition, when multiple treatment pulses are attempted, the precise location and shape of the beam is desirable.

BACKGROUND OF THE INVENTION Until recently, it had not been possible to provide a predetermined practical pattern of treatment wherein the intensity and duration of the laser pulse is controlled while simultaneously controlling the shape of the laser pulse and the location where the pulse attacks the target. It has been found that the cornea of the eye can be formed or otherwise treated with a laser beam pulse at a plurality of locations on the eye to achieve a desired result. Until now, however, the ability to control the size, shape and location of the beam has been undesirably limited. It has recently been discovered that a predetermined control of the laser beam pulse can be achieved by passing the laser beam through an iris that is centered on both the axis of the laser beam and on the optical axis of the cornea. By controlling the size of the iris opening and simultaneously controlling the amount of laser energy that passes through the iris opening, the curvature of the eye surface can be changed to correct myopia or short sight. Such a procedure, however, has not found widespread acceptance due to inherent limitations in the shape of the beam and the size that such an aperture provides. For example, the use of an iris only allows a round, symmetric alteration in the shape of the laser beam that is not useful for the treatment of astigmatism, hyperopia, irregular shapes and even repair of corrections on corrected or inadequate for myopia.

The treatment for hyperopia by means of a laser necessarily involves the removal of more corneal tissue in the periphery compared to the central region of the cornea. As a result, the use of only one variable iris opening to alter the shape of a laser beam can not achieve this objective. The teachings of the prior art, such as Yoder, Jr. U.S. Pat. No. 5,219,344, describes the use of rings of varying size to effect a greater exposure of peripheral tissue of the cornea. Notably, however, the methods and apparatus described in Yoder, Jr. also inherently require the use of shapes that are symmetrical about the axis of the laser beam and around the optic axis of the cornea. These methods are therefore inherently limited by the use of opening discs that have a limited number of rings. Additionally, the inability to vary the shape of such rings imposes additional limitations on the operator and this inability limits the degree to which the cross-sectional shape of the laser beam can be modified. Similarly, Trokel U.S. Pat. No. 5,108,388 describes a method of laser surgeries using masks having limited numbers of circular or slot-shaped openings. The limitations inherent in such a method are similar to those of Yoder, Jr. more specifically, while Trokel teaches that any suitable number of openings can be formed in the masks, the cross-sectional shape of the laser beam is however limited by the openings specific so provided. As a result, the desired flexibility to treat any given curvature malformation or combination of curvature malformations can not be achieved. In a more illustrative example of the limitations of the prior art, the treatment of hyperopia combined with an astigmatism presents an additional complicated problem as the tissue not only of the periphery but also along the main axis of the astigmatism should preferably be removed in comparison with other regions of the cornea. The methods and devices of Yoder, Jr. have significant disadvantages when applied to such a procedure since two different opening discs, one applicable to hyperopia and one applicable to astigmatism, must be used together. More importantly, and as before, the aperture discs contain a limited number of apertures from which to select to form the cross-sectional area of the laser beam applied to the cornea. As a result, to the extent that the procedure can be performed by the methods and apparatus of Yoder, Jr., inferior results are inevitably obtained. The teachings of Shimmick, and other U.S. Pat. No. 5,549,597, although they overcome certain of the disadvantages of Yoder, Jr., are limited in their application. Shimmick, et al., Whose applicants note that it is not necessarily prior art to the present invention, teach a device having variable cylinder knives that are useful in the treatment of astigmatism. This utility is limited, however, since the operation of the cylinder blades can not provide an effective treatment of hyperopia or an astigmatism combined with hyperopia. Moreover, since the teachings of Shimmick and others remain silent about any independent movement of the cylinder blades or movement of the asymmetric cylinder blades to the center line of the iris, it fails to overcome many of the limitations discovered in the art. previous.

OBJECTS OF THE INVENTION In view of the shortcomings and disadvantages of the prior art as recognized by the applicants, it is an object of the present invention to provide a system, method and device for modeling the shape of a laser beam to change the shape of the beam hitting its target. chosen one. Another object of this invention is to provide a system, method and device which is useful for modeling laser beams in asymmetric sub-portions of laser beam, including shapes that are not round. Still another object of the present invention is to provide a system, method and device capable of forming a laser beam to allow the treatment of astigmatism, hyperopia, irregular shapes and even repair corrections on corrected or inadequate for myopia.

BRIEF DESCRIPTION OF THE INVENTION It has been unexpectedly discovered that the systems, methods and devices of the present invention overcome the limitations of the prior art, without adding unnecessary complexity. More specifically, applicants have discovered that superior results in the formation of a cornea can be achieved by using methods and devices that expose a plurality of regions of the cornea to a plurality of asymmetric sub-portions of the laser beam to affect the shape of said cornea without introduce no substantial asymmetry to the shape of said cornea. Thus, applicants have discovered that by abandoning prior art teachings that rely on laser beam shapes that are substantially symmetrical around the laser beam axis, methods and devices of substantially superior flexibility, economy and practicality can be achieved. . Accordingly, aspects of the preferred method of the present invention consist in providing a laser beam having a predefined shape along a beam axis and exposing a plurality of regions of the cornea to a plurality of laser beam sub-portions. asymmetric to affect the shape of said cornea without introducing any substantial asymmetry to the shape of said cornea. As used herein, the term "asymmetric laser beam subparts" refers to portions of the laser beam that are not symmetrical about the axis of the laser beam. According to preferred embodiments, the cross-sectional shape of the laser beam sub-portion is substantially defined by a portion of the periphery of said predefined shape, with each of said sub-portions of the laser beam being produced by obstructing a portion of said laser beam to a default form.

A preferred device according to the present invention comprises means for producing a plurality of asymmetric laser beam sub-portions from a laser beam traveling along a laser beam axis. Applicants have discovered that the use, for example of a single plate movable in all directions through the path of the laser beam, or a plurality of plates operable independently through the course of the laser beam, the ability to clog a laser beam for Achieving an almost infinite variety of laser beam sub-portions can be achieved. An operator of the device can thus obstruct the beam to produce a series of laser beam sub-portions that are highly desirable in the treatment of any curvature malformation or combination of curvature malformations. As a result, the desired cornea curvature can be achieved simply and efficiently, as explained in more detail hereafter. The preferred system includes a laser source for directing a laser beam along a laser axis and a target for receiving the laser beam. The device of this invention is located in the path of the laser beam in such a way that the device is aligned in such a way that any chosen portion of the laser beam is obstructed or hidden. In a preferred embodiment, the target is the human eye and, more particularly, the cornea of a human eye. The predetermined pattern is designed to form the cornea as the laser contacts it in controlled pulses at predetermined locations on the cornea, preferably to treat astigmatism, myopia or hyperopia.

The methods of the present invention consist of a series of sequential steps in which at least two regions of the cornea are each exposed to increasingly large portions of the laser beam. As the cross-sectional area of the beam increases, the largest portion of the beam will be understood to include the preceding smaller portion as well, thereby exposing the area of the cornea previously exposed to additional laser radiation. In this way, the total area of the cornea exposed to laser radiation will be formed to the desired curvature by gradually varying the amount of exposure through the exposed area. In the preferred embodiment, two pairs of complementary regions of the cornea will be sequentially exposed to laser radiation. In each such region, a first part will be exposed to a substantially segmented portion of the beam, and then at least another part will be exposed to a substantially larger segmented portion of the beam in which the largest segmented portion includes the segmented portion. smaller. It will be understood that a complementary region of the cornea consists of that region which, when added to the region of which it is complementary, defines the total cornea area exposed to laser radiation. In a more preferred embodiment, each region of the cornea to be treated will be exposed to nearly 40 substantially segmented portions in which each subsequent portion is larger than and includes each preceding portion. It will be understood that as used herein, a substantially segmented form includes any shape defined by a substantially arcuate boundary and a substantially unbowed boundary and that the base of any such form is understood to be the substantially non-arched boundary and the arc of the boundary. any such form is understood to be the substantially arched boundary. It should be further understood that the arcuate boundary of the beam may include a transition zone through which the cross-sectional area of the beam may expand incrementally from ray portion to beam portion thereby creating a gradual ablation of the periphery of the beam. the region of the cornea thus exposed. According to certain preferred embodiments, the device used herein includes a housing and a frame on which the components that obstruct the laser beam are mounted. The control of the device can be achieved manually but it is preferred that the different components are controlled by a computer within which the desired data has been supplied. A keyboard and a video monitor are also preferably used in the system to supply data and to visualize the various treatments being performed. The device preferably includes an iris defining an aperture that is aligned perpendicular to the axis of the laser beam and, even more preferably, an adjustable iris for adjustable movement of the aperture about the axis. When an adjustable iris is used, the iris is preferably controlled by control means receiving instructions from the operator or computer program to enlarge or shrink the opening as planned. The size of the iris opening is preferably varied by an electric motor and gear assembly that allows exact adjustment of the opening dimension within the necessary tolerances. Also included in the preferred device is a means for modifying the laser beam to produce a plurality of asymmetric laser beam sub-portions from a laser beam traveling along a laser beam axis. According to preferred embodiments, the modification means consist of at least one movable plate so as to additionally obstruct a portion of the laser beam that would otherwise pass through the iris. As used herein, a plate includes a door, gate, shutter, or other similar structure that can obstruct or occlude the laser beam. Preferably, the means of modifying the beam include a pair of sections of opposite doors. In one embodiment, the beam modifying means operates the pair of door sections symmetrically about the axis, preferably in such a way that the symmetrical movement of the pair of door sections is simultaneous. In a highly preferred embodiment, the beam modification means operates the pair of door sections independently to allow the movement of one section unrelated to the movement of the other section. This independent movement and control allows substantially more flexibility in the design of the predetermined shape, size and pattern of the laser beam. The beam modification means preferably includes a motor for moving the door sections through gears that allow precise movement that is repeatable with respect to a fixed point in space such as the axis of the laser beam to provide maximum control and effectiveness of the present invention. In a preferred embodiment, each of the two door sections are operated by a separate motor. In a preferred alternate embodiment, the ray modification means includes a single plate that is capable of obstructing any portion including the entire laser beam. In this preferred embodiment, the beam modifying means preferably includes means for moving the plate to positions to obstruct substantially any and all portions of the laser beam. In the preferred embodiment in which the beam modifying means includes two independently movable door sections, the control means is also adapted to rotate the device around the axis of the laser so that the door sections are able to intercept any portion of the laser beam as desired. To achieve this object, a portion of the device is adapted to rotate both clockwise and clockwise to provide a complete circle of laser beam intersection or control. In the preferred alternate mode in which the ray modification means includes a single plate, the control means do not need but can be adapted to rotate the device about the axis of the beam since the plate alone is preferably adapted to obstruct any and all portions of the laser beam without such rotation.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, reference is made herein to the drawings, in which: Figure 1 is a schematic view illustrating the environment and operative components of the device of this invention as used in a surgical procedure corrective eye. Figure 2 is an enlarged side elevational view of the device shown in Figure 1. Figure 3 is a rear elevation or right hand view of Figure 2. Figure 4 is a front or left elevation view of the Figure 2 with a portion of the cover plate cut away to show certain details of the iris activating mechanism. Figure 5 is a sectional elevation view taken along line 5, 5 of Figure 4, showing even more detail of the iris activating mechanism and the adjustable door assembly and slot mechanism. Figure 6 is a plan view of Figure 4 showing the driving mechanism for the angular arrangement of the door and slot mechanism. Figure 7 is a fragmentary, enlarged sectional view taken on line 7, 7 of Figure 2 showing further details of the driving mechanism for the doors and the driving gear for the rotational position of the door assembly. Figure 8 is a schematic, enlarged view showing the general arrangement of the system of this invention for a surgical procedure on the eye to correct myopia. Figure 9 is a view similar to Figure 8 for a surgical procedure to correct hyperopia. Figure 10 is a view similar to Figures 8 and 9 for astigmatism. Figure 11 is a front view, on a reduced scale, showing the main axis of a cornea in elliptical form.

DETAILED DESCRIPTION OF PREFERRED MODALITIES THE SITEMAS AND DEVICES As shown in the drawings, a system for modeling a laser beam has been developed to control the laser beam as it acts on the target for which it was designed. The system, generally at 10, includes a laser source 11 which directs a laser beam source 13 along an axis 15 through the device of this invention, generally at 17, in which the laser beam is modeled as shown in FIG. describes in the present. The modeled beam then passes through a focus lens assembly 19, is directed by a mirror 21, and reaches a target such as an eye 23. The focus lens assembly 19 and the mirror 21 are used to align the beam laser properly with respect to the target once the system has been mounted on a suitable table. The device 17 is controlled by a computer 27 having a circuit board installed inside a computer, such as an IBM PC or a compatible IBM computer. The computer is programmed through a keyboard 29 to provide a predetermined pattern of action for the laser, such as, for example, the laser pattern and the number of laser pulses for a corneal surgery treatment to correct astigmatism, myopia , or hyperopia. The video monitor 31 allows the operator to review the measured or programmed data and visualize the various treatments being performed. The computer program provides instructions to the device 17 to operate four axes of movement. The laser beam is modeled by passing the beam through the device 17 in such a way that an iris opening and preferably two doors cross the beam in a predetermined pattern. A foot activated switch 33 allows the operator to send activation signals to the system while maintaining control over the patient by allowing the operator to position or adjust the target, such as the cornea of a human eye. With the laser beam pulsed, the target is modeled each time according to the predetermined program, either from a computer program or from an operator's direct power data. Note also that when the switch 33 activated per foot is used, the operator is also free to use the keyboard 29 at any time. The system of this invention is capable of automated operation with the total treatment regime being programmed into the computer so that all that is necessary is to place the patient and start the operation. Alternatively, a doctor may choose to manually supply each succeeding pulse or group of laser pulses depending on the results of the preceding pulse or group of pulses. Turning now to the device shown generally at 17 in Figure 1, it can be seen that the cables connect the device to the control means through the computer 27 and the circuit board 35 to control a first motor 37 through the cable 39 and receive feedback from the first encoder 41 through the cable 43. Similarly the second motor 45 receives power from the cable 47 and the second encoder 49 provides the necessary feedback to the computer 27 through the cable 51. The first and second motor 37 and 45 are mounted about what is described as the front part of the device 17, wherein the axis of the laser 15 enters the modeling device. On the rear side of the device 17 are a pair of motors 53 and 55, shown in FIGS. 2 and 3, which are controlled by supply cables 57 and 59 respectively and provide feedback through the cables 61 and 63 respectively. The modeling device 17 includes an iris shown in Figure 4 with an aperture 67 that changes in size as the iris diaphragm 69 is changed. The diaphragm 69 is controlled by a clasp 71 mounted on the ring gear 75. The clockwise movement of the ring gear 75 opens the opening 67 while the counter-clockwise movement of the ring gear 75 closes the diaphragm 69 and therefore the opening 67. Figure 5 illustrates how the ring gear 75 is mounted by supports 77 on the flange 79, with the iris 65 also being mounted on the flange 79. The flange 79 is fastened to the iris retaining ring 83 by the clasp 81, with the iris 65 contained within the retaining ring 83. A screw of. The centrally located large machine 85 secures the retaining ring 83 within a vertically upright housing block 87 also shown in Figure 5, is the clasp 71 extending through the arched groove 73 in the flange 79 to the iris 65. This ring gear 75 iris activator is driven, by commands from the control board as previously described, by the second iris motor 45, which rotates to the gear bracket 89 on the arrow 91 of the motor 45. The movement of this iris diaphragm 69 is the first axis of movement for the present invention, illustrated by the arrows 93 in Figure 4. On the right side of the device 17 shown in Figure 2, also known as the back or exit side, there are a pair of door sections 95 and 97 respectively. Figure 7 illustrates the manner in which the upper door section 85 is driven by the motor 53 and the associated screw arrow 101, which arrow is in turn screwed into the door section 95 by the screw portion 103. The lower end 105 of the arrow 101 passes through the clearance passage 107 in the lower door section 97.The motor mounting block 1 19 mounts the two motors 53 and 55 in such a way that they are secured in the holes in the block 1 19 by means of fixing screws 99. The output arrows of the motors 53 and 55 are adhered inside of the upper terminal ends of two screw arrows 101 and 1 1 1 respectively. The screw arrows 101 and 11 are respectively mounted on supports 102 and 112 on the inferred face of the block 119. The lower terminal ends of the screw arrows 101 and 11 are carried on supports 104 and 14, respectively, in the lower mounting block 106. The upper door 95 threadably engages the threaded portion 103 of the screw shaft 101 and is urged up or down by the motor 53. The lower door section 97 threadably engages the threaded portion 113. of the screw arrow 111 and is driven up or down by means of the motor 55. The two door sections 95 and 97 are stabilized for up and down movement using two guide rods 108 and 110 that extend between the block upper 1 19 and the lower mounting block 106. The guide rods 108 and 1 10 are secured by means of fixing screws 1 16 in the upper block 1 19. The two sections Door Nos. 95 and 97 each have linear supports 120 mounted on their outer ends for coupling with guide rods 108 and 1 10. The complete door assembly is mounted to the gear face 127 by means of two screws 121 in the block upper 119 and two similar screws 121 in the lower mounting block 106.

Similarly, the motor 55 and the associated screw arrow 1 1 1 activate the door section 97 through the screw portion 13 so that the upper end 115 of the arrow 111 has clearance for the upper door section 95 through the release step 117. The engine mounting block 119 assembles the engines 53 and 55 which in turn move the door sections 95 and 97 respectively in the direction shown by the arrows 123 and 125 in Figure 3, for example, as to restrict the passage of a laser beam through the opening 67 along the axis 15. In the preferred embodiment shown here, the door section 95 is moved by the motor 53 regardless of whether or not it is The door section 97 is moved by the motor 55, and, of course, the opposite is also true because both motors 53 and 55 are controlled and activated separately, depending on the predetermined pattern. In this way one side or the other of the laser beam pulse can be larger or smaller than the other side as desired. The complete door means including the motors 53 and 55 are mounted on the motor mounting block 119, whose block 1 19 is adhered to a ring gear 127 by screws 121. The ring gear 127 is mounted on brackets 129, a once mounted on flange 131. The flange 131 is adhered by machine screws 133 to the housing block 87. Figure 3 illustrates the final axis of motion of the modeling device 17. The ring gear 127 moves in the direction of the arrow 135 by the gear strut 137 on the drive shaft 139 of the motor 37. The motor 37 rotates the arrow 139 and the gear strut 137 in the direction of the arrow 141, rotating the ring gear 127 about the shaft 15 by 180 ° in both the clock direction and in the counter-clockwise direction. The machine limit screws 143 and 145 limit the trip to 180 ° with the contact with the limit stop 147 in the lower part of the accommodation block 87. The device shown in figure 7 is limited to approximately but not less than 180 ° of movement in each direction but other limits are possible as desired. It may be possible to travel the complete 360 ° with a different assembly. In all positions, the encoder 41 provides feedback to the controller as the angular position of rotation about the axis 15 in the direction of the arrow 135. Similarly, the encoder 49 provides feedback to the controller as for the angular position of the iris diaphragm 69, and thus the aperture size 67. The motors 53 and 55 are also provided with internal encoders at the top thereof to provide feedback as for the position of the door sections 95 and 97 indicating the position of the screw 103 in the door section 95 and the screw 113 in the door section 97. The modeling device 17 can be adjusted or repaired by the removal of the plate of lock 147 in angular form. The motors 37 and 41 are mounted to the housing block 87 through machine screws 153. The screws 153 also serve to hold the lock plate 149 in place as it rests on the step 155, covering the mechanisms within the block. 87, leaving a space between the lock plate 149 and a ring gear 175 as shown in Figure 5. The shape of the lock plate 159 is shown in Figure 4 where the left side of the plate lock 149 is in shaded lines in part to show the location of engines 37 and 41, among other things. Figure 6 is a top plan view illustrating the grooves 157 in the base plate 159 which allow the precise assembly and location of the complete modeling device 17 on the table 25 so that it can be properly oriented with respect to a laser 1 1 and the other components illustrated in figure 1 .

METHODS In addition to the devices and systems described above, the present invention provides methods that have great utility in the treatment of poor functions of optical organs in animals, particularly human corneas. For example, it can now be seen that the modeling device 17 can be operated to restrict the travel of the laser beam along the axis of the laser beam 15 in four ways. First, the aperture 67, which can be enlarged or made smaller by the iris diaphragm 69, circumferentially restricts the laser beam, as for use in certain treatments such as myopia. In addition, the block sections 95 and 97 can be moved, independently in this embodiment, to further restrict the laser beam on one side or both sides as the predetermined pattern required for the second and third restriction axes. Finally, the total assembly can be rotated about the fourth axis, which is the axis of the laser beam, so that any door section 95 or 97 or both sections, can restrict a different portion of the laser beam. As noted above, the present invention is admirably suitable for use in eye surgery, and more particularly for the treatment of the eye to correct astigmatism, myopia, or hyperopia. Figure 8 illustrates the general arrangement of the device 17 as the laser beam 13 passes along the axis 15, from left to right in the drawing, to first press on the diaphragm 69 of the iris 65 and pass through that portion of the laser beam pulse that fits within the aperture 67. The laser beam pulse is not restricted by the door sections 95 and 97, shown in position immediately to the ring gear 127, in turn supported as previously described on the support 129 on the tab 131. The eye 175 and the cornea, 177 are treated for myopia by the system of this configuration. The door sections 95 and 97 are fully open and the iris diaphragm 69 is completely closed. The laser is then pulsed one or more times at several predetermined locations as the iris opens at predetermined increments. Dotted line 179 illustrates the flattened cornea after treatment.

Figure 9 illustrates a configuration of the present invention as for hyperopia treatment in which the opening 67 is open to a predetermined diameter. According to preferred methods of the present invention, the cornea 175 is exposed to a plurality of asymmetric laser beam sub-portions to affect a substantially symmetric correction in the shape of the cornea. According to a preferred embodiment, the upper door section 95 is open at its maximum spacing and the lower door section 97 is raised to a chordal cutting position to exclude a large portion of the laser beam pulse and thus create a laser beam sub-portion that is asymmetric around the laser axis. A plurality of cornea regions can then be exposed to a plurality of laser beam sub-portions by: rotating the door portions around the laser axis and exposing the cornea to radiation in a plurality of such indexed positions; and / or obstructing a smaller portion of the laser beam by opening the door portion 97 and exposing the cornea to radiation in a plurality of such positions. The method can thus be used to achieve the results 183 on the cornea 177 to produce hyperopic treatment. Figures 11-16 provide a diagrammatic view of the operation of preferred embodiments of the present method. Figures 11a-11f illustrate the shape of a laser beam after successive exposures to a cornea according to an embodiment of the present invention. In these figures, the predetermined cross-sectional shape of laser beam 200 is circular, as represented by Figure 11a. It will be appreciated, of course, that all varieties of predetermined shapes are adaptable for use in accordance with the present invention. The first exposure of the cornea includes obstructing the beam to produce a beam subportion having a configuration 201 as shown in Fig. 11b to produce a segment of the circle that defines the predefined original shape. According to one embodiment, the second, third, fourth and fifth exposure of the cornea includes obstructing the beam to produce a plurality of beam sub-portions having the configurations 202-205 shown in Figures 11c-11f. Such a plurality of beam sub-portions can easily be achieved by the device of Figure 9 by rotating the doors through series of predefined angles. In general, it is preferred and contemplated that the present methods include increasing the size of the laser beam sub-portions and re-exposing the cornea to a plurality of such beam sub-portions, as shown in Figures 12b and 12f. It will be readily apparent to those skilled in the art that numerous variations on the illustrated embodiments are available within the scope of the present invention. For example, although the lightning sub-portions in Figures 11a-1f are shown as not to be substantially enclosed, this is certainly not required, and in fact it is contemplated that each beam sub-portion may include a portion of a previous beam sub-portion or subsequent, as is the case in figures 12b-12f. In addition, the size and relative angle of rotation of the subsequent ray sub-portions may be the same or different, depending on the desired result. It will be appreciated by those skilled in the art, however, that the present methods are adaptable to effectively and efficiently treat hyperopia using a plurality of asymmetric beam sub-portions to produce a change in the shape of the cornea without introducing any substantial asymmetry to the cornea . Figures 13a-13f provide a diagrammatic view of the operation of another preferred embodiment of the present methods. In these figures, the predefined cross-sectional shape of laser beam 300 is also circular, as represented by FIGS. 13a, again being appreciated that all varieties of predefined shapes are adaptable for use. The first exposure of the cornea includes obstructing the beam to produce a beam sub-portion having a configuration 301 as shown in Figure 13b to produce a segment of the circle that defines the predefined original shape. According to one embodiment, the second, third, fourth and fifth exposure of the cornea includes obstructing the beam to produce a plurality of beam sub-portions having the configurations 302-305 shown in Figures 13c-13f. Such a plurality of beam sub-portions can be quickly achieved by the device of Figure 9 by simply increasing the opening of the doors in the device shown in Figure 10. According to a preferred embodiment, after being exposed to the laser beam sub-portions as is illustrated in Figures 13b-13f, the doors are indexed 90 ° around the axis of the laser beam and the exposure treatment is repeated with the doors creating a series of laser beam sub-portions 401-405 with the doors rotated to this position. All exposures of this 90 ° rotation are shown in compressed form in Figure 14. The operation is then repeated with the doors at 180 ° to produce the sub-portions 501-505 and at 270 ° to produce the sub-portions 601-605, as shown in FIG. shows in compressed form in figures 15 and 16. In preferred embodiments of the methods illustrated in the figures 13-15, the diameter of the predefined laser beam is about 8 mm and the steps illustrated in Figures 13b-13f consist of opening the doors almost 40 times in increments of 0.1 mm until the laser beam is bisected substantially to produce a semicircular subporción. This procedure is repeated afterwards for each of the quadrants illustrated in Figures 14-16. Figure 10 illustrates a treatment condition for astigmatism in which both the upper door section 95 and the lower door section 97 converge to an almost closed position, as shown, to form a thin slit. In this procedure, the door assembly does not rotate more than initially when it aligns the groove band 185 to the main axis 186 of the elliptically formed cornea. Again, this method is repeated over predetermined variant increases in slit bandwidth to achieve results 190 on the cornea 177. As will be apparent from the reading of the aforementioned, the doors and irises of the modeling device of this invention can be manipulated to project a wide variety of laser beam patterns onto a target such as, for example, the human eye. Such patterns include, by way of example and not limitation, rings of various sizes, segments, ellipses, ovals and other curved shapes. In addition, the use of the door sections along the entire periphery of the beam, in sequential steps, allows the projection of straight edge shapes, such as rectangles and the like. Although the particular embodiments of the present invention have been described and illustrated, they are not designed to limit the invention. Other embodiments, forms and modifications of the invention that come within the scope and spirit of the appended claims, of course, will readily be suggested to those skilled in the art as well.

Claims (5)

NOVELTY OF THE INVENTION CLAIMS

1. A method for applying a laser radiation beam of tissue ablation to affect the shape of a cornea without introducing any substantial asymmetry to the shape of said cornea, the method consisting of the steps of exposing the cornea to laser radiation comprising of the steps of: (a) providing a laser beam having a predefined shape along a beam axis; and (b) exposing a plurality of cornea regions to a plurality of laser beam sub-portions to affect the shape of the cornea without introducing any substantial asymmetry to the shape of the cornea, the laser beam sub-portions each being asymmetric with respect to the laser beam axis and having a cross-sectional shape substantially defined by a portion of the periphery of the predefined shape, each of the sub-portions of the laser beam being produced by obstructing a portion of the beam in a predefined manner. 2.- A method to apply a laser radiation beam of ablation of tissue to affect the shape of a cornea, the method consists of the steps of exposing the cornea to laser radiation consisting of the steps of providing a laser beam that has a predefined shape along a ray axis and sequentially: (a) exposing a series of first successive region of the cornea to a first sub-portion of the laser beam, the first sub-portion of the ray being asymmetric with respect to the laser beam axis and having a cross-sectional shape substantially defined by a portion of the periphery of the predefined shape, the sub-portion of the laser beam being produced by obstructing a portion of the beam in a predefined manner; and (b) exposing at least a second region of the cornea to a second sub-portion of the laser beam, the second sub-portion of the beam being asymmetric with respect to the laser beam axis and having a substantially defined cross-sectional shape by a portion of the periphery of the predefined shape, the subportion of the laser beam being produced by obstructing a portion of the beam in a predefined manner; a segmented shape consisting of a base and an arc wherein at least a portion of the arc of the second portion of the spoke coincides with the arc of the first portion of the spoke and wherein the second portion of the spoke is longer than the first portion of the ray and includes the entire first portion of the beam, the second portion of the beam being produced by obstructing the beam; (c) exposing a second region of the cornea to laser radiation wherein the second region is complementary to the first region of the cornea that consists of the steps of sequentially: (i) exposing a first part of the second region of the cornea to a third portion of the beam, the third portion of the beam having a segmented shape consisting of a base and an arc and being produced by obstructing the beam; and (ii) exposing at least a second part of the second region of the cornea to a fourth portion of the beam, the fourth portion of the beam having a segmented shape consisting of a base and an arch where at least a portion of the arch of the The fourth portion of the ray is coincident with the arc of the third portion of the ray and where the fourth portion of the ray is longer than the third portion of the ray and includes the entire third portion of the ray, the fourth portion of the ray being produced by obstructing the Thunderbolt; (d) exposing a third region of the cornea to laser radiation consisting of the steps of sequentially: (i) exposing a first part of the third region of the cornea to a fifth portion of the ray, the fifth portion of the ray having a segmented form consisting of a base and an arc in which a line coinciding with the base of the fifth portion of the ray is perpendicular to a line coincident with the base of the first portion of the ray, the fifth portion being produced by obstructing the ray; and (ii) exposing at least a second part of the third region of the cornea to a sixth portion of the beam, the sixth portion having a segmented shape consisting of a base and an arch where at least a portion of the arch of the sixth portion of the ray is coincident with the arc of the fifth portion of the ray and where the sixth portion of the ray is longer than the fifth portion of the ray and includes the entire fifth portion of the ray, the sixth portion of the ray being produced by obstructing the ray; and (e) exposing a fourth region of the cornea to laser radiation wherein the fourth region is complementary to the third region of the cornea that consists of the steps of sequentially: (i) exposing a first part of the fourth region of the cornea to a seventh portion of the ray, the seventh portion of the ray having a segmental form consisting of a base and an arc and being produced by obstructing the ray; and (i) exposing at least a second part of the fourth region of the cornea to an eighth portion of the ray, the eighth portion of the ray having a segmental shape consisting of a base and an arch where at least a portion of the arch of the eighth portion of the ray is coincident with the arc of the seventh portion of the ray and where the eighth portion of the ray is longer than the seventh portion of the ray and includes the entire seventh portion of the ray, the eighth portion of the ray being produced by obstructing lightning. 3. A method for applying a beam of tissue-softening laser radiation to affect the shape of a cornea, the method consisting of the steps of: (a) exposing a first region of the cornea to laser radiation consisting of the sequentially steps: (i) exposing a first part of the first region of the cornea to a first portion of a laser beam, the beam having a substantially circular cross section, the first portion of the ray having a segmental shape consisting of a base and an arc and being produced by obstructing the beam; and (ii) exposing at least a second part of the first region of the cornea to a second portion of the beam, the second portion of the beam having a segmented shape! consisting of a base and an arc in which at least a portion of the arc of the second portion of the beam is coincident with the arc of the first portion of the beam and wherein the second portion of the beam is longer than the first portion of the beam and includes all the first portion of the beam, the second portion of the beam being produced by obstructing the beam; and (b) exposing at least a second region of the cornea to laser radiation consisting of the steps of sequentially: (i) exposing a first part of at least the second region of the cornea to a third portion of the beam, the third portion of the beam having a segmented shape! consisting of a base and an arc where the base of the third portion is angularly oriented to the base of the first portion of the beam, the third portion of the beam being produced by obstructing the beam: and (ii) exposing at least a second part of the beam. at least the second region of the cornea to a fourth portion of the ray, the fourth portion of the ray having a segmental shape consisting of a base and an arch where at least a portion of the arc of the fourth portion of the ray is coincident with the arc of the third portion of the beam and where the fourth portion of the beam is larger than the third portion of the beam and includes the entire third portion of the beam, the fourth portion of the beam being produced by obstructing the beam. 4. A method for applying a beam of tissue softening laser radiation to affect the shape of a cornea, the method consisting of the steps of: (a) exposing a first region of the cornea to laser radiation consisting of the sequentially steps: (i) exposing a first part of the first region of the cornea to a first portion of a laser beam the first portion of the beam being produced by obstructing the beam; and (ii) exposing at least a second portion of the first region of the cornea to a second portion of the beam wherein the second portion of the beam is larger than the first portion of the beam and includes the entire first portion of the beam, the second portion. portion of the beam being produced by obstructing the beam; and (b) exposing at least a second region of the cornea to laser radiation consisting of the steps of sequentially: (i) exposing a first part of at least the second region of the cornea to a third portion of the beam, the third portion of the beam being produced by obstructing the beam; and (ii) exposing at least a second part of the second region of the cornea to a second portion of the beam wherein the second portion of the beam is larger than the first portion of the beam and includes the entire first portion of the beam, the second portion. portion of the beam being produced by obstructing the beam. 5. A method for applying a laser radiation beam of tissue ablation to affect the shape of a cornea, the method comprising the steps of: (a) exposing a first region of the cornea to laser radiation consisting of the sequentially steps: (i) exposing a first part of the first region of the cornea to a first portion of a laser beam, the beam having a substantially circular cross section, the first portion of the ray having a segmented shape consisting of a base and an arc and being produced by obstructing the beam; and (ii) exposing at least a second part of the first region of the cornea to a second portion of the beam, the second portion of the beam having a segmented shape consisting of a base and an arc where the base of the second portion of the beam is spaced from and parallel to the base of the first portion of the beam and wherein the second portion of the beam is larger than the first portion of the beam and includes the entire first portion of the beam, the second portion of the beam being produced by obstructing the beam; (b) exposing a second region of the cornea to laser radiation wherein the second region is complementary to the first region of the cornea that consists of the steps of sequentially: (i) exposing a first part of the second region of the cornea to a third portion of the beam, the third portion of the beam having a segmented shape consisting of a base and an arc and being produced by obstructing the beam; and (ii) exposing at least a second part of the second region of the cornea to a fourth portion of the beam, the fourth portion of the ray having a segmented shape consisting of a base and an arc where the base of the fourth portion of the ray is spaced from and parallel to the base of the third portion of the beam and where the fourth portion of the beam is larger than the third portion of the beam and includes the entire third portion of the beam, the fourth portion of the beam being produced by obstructing the beam; (c) exposing a third region of the cornea to laser radiation consisting of the steps sequentially: (i) exposing a first part of the third region of the cornea to a fifth portion of the beam, the fifth portion of the beam having a segmented form consisting of a base and an arc in which a line coinciding with the base of the fifth portion of the ray is perpendicular to a line coincident with the base of the first portion of the ray, the fifth portion being produced by obstructing the ray; and (ii) exposing at least a second part of the third region of the cornea to a sixth portion of the ray, the sixth portion of the ray having a segmented shape consisting of a base and an arch where the base of the sixth portion of the ray is spaced from and parallel to the base of the fifth portion of the beam and where the sixth portion of the beam is longer than the fifth portion of the beam and includes the entire fifth portion of the beam, the sixth portion of the beam being produced by obstructing the beam; and (d) exposing a fourth region of the cornea to laser radiation wherein the fourth region is complementary to the third region of the cornea that consists of the steps of sequentially: (i) exposing a first part of the fourth region of the cornea to a seventh portion of the ray, the seventh portion of the ray having a segmented form consisting of a base and an arc and being produced by obstructing the beam; and (ii) exposing at least a second part of the fourth region of the cornea to an eighth portion of the ray, the eighth portion of the ray having a segmented form consisting of a base and an arc where the base of the eighth portion of the ray is spaced from and parallel to the base of the seventh portion of the beam and where the eighth portion of the beam is larger than the seventh portion of the beam and includes the entire seventh portion of the beam, the eighth portion of the beam being produced by obstructing the beam .