Abstract:
A device for simulating ophthalmic surgery is disclosed which comprises a laser for generating a laser beam, an array for sensing whether the laser beam has been projected at the array, and a computer system operatively connected to the laser and the array, the computer system for actuating the laser, for determining whether the array has sensed the laser beam, and for creating an ablation profile based upon whether the array has sensed the laser beam.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device and method for reshaping a corneal surface of an eye for refractive correction by laser ablation, and more particularly to a device and method for simulating the reshaping of the corneal surface. 
     Various lasers have been employed for ophthalmic surgery applications including the treatment of various eye disorders such as glaucoma, cataract, myopia, hyperopia, and astigmatism. In order to correct some of these eye disorders a laser is used to ablate or remove a portion of the corneal surface of an eye in order to reshape the cornea. Typically, such laser refractive surgery is achieved through a plurality of ablated layers, the cumulative affect of the plurality of ablated layers attempting to remove a portion of the cornea to reshape the cornea to correct the curvature of the eye. However, before attempting laser surgery on the cornea, most laser systems in use require the ophthalmologist to practice the ablation on a piece of plastic or metal. Once the practice piece is completed it is necessary to estimate the corresponding depth of ablation in the cornea by using one or more conversion factors. Such conversions or estimates are only approximations and do not completely and accurately determine the depth of ablation. In some situations such estimates are no more than an educated guess that the ablation profile performed on the practice piece will correct an eye disorder in an actual human eye. Additionally, in one available system, the EXCALIBER manufactured by LaserSight Technologies, a visual profile of the ablated cornea is created. However, with the EXCALIBER, a test ablation is still performed on a plastic sample and the profile is created through estimated conversion factors. 
     It would be advantageous if a simulated ablation profile of a cornea could be constructed or generated without the use of a practice or test piece of synthetic material. The present invention is designed to obviate and overcome many of the disadvantages and shortcomings experienced with the use of a practice piece of material. The present invention eliminates the test ablation on a synthetic material and a computer is used to directly translate actual laser energy pulses into a three dimensional view of corneal stroma ablation. In this manner, the present invention simulates ophthalmic surgery for correcting a disorder of an eye without actually performing surgery on an eye. 
     SUMMARY OF THE INVENTION 
     The device for simulating ophthalmic surgery of the present invention comprises laser means for generating a laser beam, an array for sensing whether the laser beam has been projected at the array, and a computer system operatively connected to the laser means and the array, the computer system for actuating the laser means, for determining whether the array has sensed the laser beam, and for creating an ablation profile based upon whether the array has sensed the laser beam. 
     In another form of the present invention, a device for simulating an ablation profile of a cornea of an eye comprises a laser for producing a laser beam, an array of sensing devices for sensing whether the laser beam has been projected onto any of the sensing devices of the array, and a computer system operatively connected to the laser and the array, the computer system for actuating the laser and for determining whether any of the sensing devices of the array has sensed the laser beam, the computer system further producing a simulated ablation profile for determining whether the simulated ablation profile will correct an abnormal condition of an eye. 
     In still another form of the present invention, a method of simulating ophthalmic surgery comprises the steps of providing a laser for producing a laser beam, providing an array of sensor devices for sensing whether the laser beam has been projected at the array, and providing a computer system operatively connected to the laser and the array, the computer system for actuating the laser, for determining whether the array has sensed the laser beam, and for creating an ablation profile based upon whether the array has sensed the laser beam. 
     In light of the foregoing, it will be recognized that a principal object of the present invention is to provide an improved device for simulating ophthalmic surgery for correcting a disorder of an eye. 
     A further object of the present invention is to provide a device for simulating ophthalmic surgery which can be easily employed with highly reliable results. 
     Another object of the present invention is to provide a device for simulating ophthalmic surgery which can simulate the ablation profile of the cornea by directly translating actual laser energy pulses into a three dimensional view of the cornea. 
     A still further object of the present invention is to provide a device for simulating ophthalmic surgery which provides an energy profile which accurately predicts an ablation profile of the cornea and a keratometric appearance of an eye to be treated. 
     These and other objects and advantages of the present invention will become apparent after considering the following detailed specification in conjunction with the accompanying drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic view of a device for simulating ophthalmic surgery constructed according to the present invention; 
     FIG. 2 is a flow chart of a program utilized to control the operation of the device shown in FIG. 1; 
     FIG. 3 is a block diagram of a second preferred embodiment of a device for simulating ophthalmic surgery constructed according to the present invention; 
     FIG. 4 is a diagrammatic view of a third preferred embodiment of a device for simulating ophthalmic surgery having a fiber optic grid; 
     FIG. 5 is a perspective view of another fiber optic grid constructed according to the present invention; and 
     FIG. 6 is a partial cross-sectional view of the fiber optic grid shown in FIG. 5 taken along the plane of line  6 — 6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein like numerals refer to like items, number  10  identifies a preferred embodiment of a device for simulating ophthalmic surgery. The device  10  includes a laser  12  which is operable to produce a laser beam  14  which is directed to an array  16 . A computer system  18  is operatively connected to the laser  12  by electrical wires or leads  20  and to the array  16  via leads  22 . The energy of the laser beam  14  is measured prior to being directed at the array  16  and this information is stored in the computer system  18 . It is assumed that the energy of the laser beam  14  will remain constant. In operation the computer system  18  actuates the laser  12  to produce the laser beam  14  which is directed at the array  16 . The array  16  includes a grid  24  of sensing elements  26  which sense whether the laser beam  14  has been directed at a particular element  26  in the grid  24  and the duration of time that the laser beam  14  was sensed by the particular element  26 . The elements  26  may be for example, photovoltaic, galvanometric, or electronic sensors and are arranged to each cover a 1 mm 2  surface area. For example, when the laser beam  14  strikes the element  26  of the grid  24  a signal is sent over wires  22  to the computer system  18  to indicate that the element  26  sensed the laser beam  14  and the duration of time that the laser beam  14  struck the element  26 . With this information and the previously measured energy data, the computer system  18  is able to generate or simulate an ablation profile of the cornea of the eye without having to ablate the cornea or a sample piece such as a piece of plastic or metal. Additionally, the computer system  18  is able to determine if the simulated ablation profile matches a predetermined ablation profile. This allows the device  10  to verify that the simulated ablation profile will successfully correct for an abnormal condition of an eye. Additionally, the computer system  18  is capable of determining the power of the laser beam  14  at each element  26  within the array  16  and the time that the laser beam  14  is sensed by each element  26 . Some of the elements  26  within the array  16  will be hit by the laser beam  14  more than once and the computer system  18  is able to record the total energy cumulatively for each element  26  within the array  16 . Again, with this information, the computer system  18  can determine the ablation profile and the computer system  18  also creates a three dimensional (3-D) view of the simulated ablation profile. The computer system  18  is used to directly translate actual laser energy pulses into a 3-D view of corneal stromal ablation. The 3-D view allows the ophthalmologist to predict keratometric changes to the cornea to be treated. The 3-D view may also be presented on a monitor (not shown) which is part of the computer system  18 . Also, the array  16  tests the alignment of the laser beam  14 . 
     The device  10  shown in FIG. 1 is operable to perform the aforementioned procedure according to a program  100  which may be loaded into the computer system  18 . An exemplary flow chart of such a program  100  is illustrated in FIG.  2 . Referring now to FIG. 2, the control of the program  100  begins at a start step  102  and proceeds to a step  104  which determines the final profile to be ablated from the cornea. Once the final ablation profile has been calculated, control of the program  100  continues to a step  106  in which the laser  12  is actuated to generate the laser beam  14  which is directed at the array  16 . At a step  108 , signals from the array  16  are sent to the computer system  18  and such signals are stored therein. The program  100  then passes to a step  110  in which a simulated profile of the cornea is generated. In a step  112 , the computer system  18  compares the final profile with the simulated profile to determine if it matches within a predetermined limit. If it does, the program  100  branches to a step  114  where the program  100  stops. If, at step  112  it is determined that the final profile and the simulated profile do not match, then control of the program transfers to a step  116 . In step  116  a redetermined final ablation profile is calculated. Once calculated, control of the program  100  passes to step  106  until the final profile matches the simulated profile in step  112 . 
     FIG. 3 depicts a scanning type laser system  200  which includes a laser  202  which is operable to produce a pulsed output laser beam  204  which is directed to a scanning device  206 . The scanning device  206  is operatively connected to a computer system  208  for control thereby, which computer system  208  may be located within the device  200 . Such operative connection may be made by way of electrical leads  210 . The laser  202  is also connected to the computer system  208  via electrical wires  212  with the computer system  208  controlling the laser  202 . A scanned beam  214  departs from the scanning device  206  and is directed to other optics components  216  which may be utilized for shaping the scanned beam  214 . A shaped scanned beam  218  is directed to a reflecting mirror  220  and a reflected beam  222  is directed onto an array  224 . The scanning device  206  is operated to control the scanning of the pulsed output laser beam  204  across the array  224 . The array  224  comprises a grid  226  of sensing elements  228  which are arranged in a rectangular fashion. The computer system is connected to the array  224  by leads  230 . The computer system  208  is used to actuate the laser  202  to produce the reflected beam  222  onto the array  224 . Once the beam  222  hits any element  228  within the grid  226 , a signal is sent over the leads  230  and stored in the computer system  208 . Information concerning all of the elements  228  which were hit, how long, and how often, is used by the computer system  208  to simulate an ablated cornea. Each pulse of the laser beam  222  is recorded by the computer system  208  and the total energy is cumulatively stored for each element  228  within the grid  226  of the array  224 . The computer system  208  is used to directly translate actual laser energy pulses into a 3-D view of corneal stromal ablation. The 3-D view allows the ophthalmologist to easily predict keratometric changes to the cornea to be treated. 
     With reference now to FIG. 4, a third preferred embodiment or device  300  of the present invention is shown. The device  300  includes a laser  302  which may be actuated to produce a laser beam  304  which is directed at an array  306 . The array  306  consists of a grid  308  of a bundle of fiber optic elements  310 . The fiber optic elements  310  are adapted to sense or receive the laser beam  304 . The fiber optic elements  310  are flexible and tubular in shape and are capable of transmitting light, such as the laser beam  304 , which is emitted into one end and out the other end. A computer system  312  is connected to both the laser  302  and the array  306  by leads  314  and  316 , respectively. The computer system  312  is used to control the operation of the laser  302  and to receive signals from the array  306  as to whether any of the fiber optic elements  310  has sensed the laser beam  304  and the duration of time that the laser beam  304  was sensed. When the computer system  312  receives the signals from the array  306 , the program within the computer system  312  can determine a simulated ablation profile for a cornea. With this information the computer system  312  can determine whether the simulated ablation profile matches a predetermined ablation profile. 
     FIG. 5 depicts another fiber optic array  350  which is shaped to simulate a cornea of an eye. The array  350  includes a bundle of fiber optic elements  352  which may be used in the device  300  in place of the array  306 . Each fiber optic element  352  is adapted to sense whether the laser beam  304  has been projected at the element  352 . Additionally, each element  352  is tubular in shape and capable of transmitting light along its length. The diameter of each element  352  may be for example 1 mm. FIG. 6 is a cross-sectional view of the fiber optic array  350  shown in FIG. 5 taken along the plane of line  6 — 6 . The array  350  is shown to include the bundle of fiber optic elements  352  with each of the elements  352  being positioned to simulate the curvature or the contour of the cornea of the eye. For example, the center fiber optic element  354  is shown as the longest element and projects out from the other elements  352 . In this manner, the array  350  can better simulate a cornea of an eye to be ablated. 
     From all that has been said, it will be clear that there has thus been shown and described herein a device for simulating ophthalmic surgery which fulfills the various objects and advantages sought therefor. It will be apparent to those skilled in the art, however, that many changes, modifications, variations, and other uses and applications of the subject device are possible and contemplated. All changes, modifications, variations, and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is limited only by the claims which follow.