WO1995015134A1

WO1995015134A1 - Laser system for reshaping the cornea

Info

Publication number: WO1995015134A1
Application number: PCT/US1994/013792
Authority: WO
Inventors: Michael J. Berry; David R. Hennings; Arthur V. Vassiliadis
Original assignee: Sunrise Technologies, Inc.
Priority date: 1993-12-02
Filing date: 1994-12-02
Publication date: 1995-06-08
Also published as: AU683709B2; AU1333495A; JPH09506521A; EP0731677A1; CA2177580A1

Abstract

Systems that deliver radiation in a defined pattern to a cornea (50) or other surface of the human body for the purpose of controllably shrinking collagen tissue beneath the surface and, as a result, causing the surface to become contracted or reshaped. In one embodiment, a coupler (125) is shaped on one side to closely contact an anterior surface the cornea and includes holes (171, 173) part way through it from its other side for receiving ends of optical fibers (133, 137). The optical fibers are illuminated with infra-red radiation from diode lasers (127, 129).

Description

LASER SYSTEM FOR RESHAPING THE CORNEA

Background of the Invention Surface tissue of a human body may be affected by directing infra-red radiation through the surface in a defined pattern to heat and shrink underlying tissue. Shrinkage of the underlying tissue causes the surface tissue to be contracted or otherwise reshaped in some desired manner. This is thought to be the result of shrinkage of collagen connective tissue which exists as a core in many structures of the body. The infra-red radiation ideally raises the temperature of the collagen tissue, according to the defined pattern, to a level which causes it to shrink but not so high that the collagen tissue is damaged in a way that stimulates a wound healing response. It is believed that such tissue damage results in regression by stimulating the production of collagen.

An example of this is a procedure to reshape a cornea of a human eye in order to correct for a refractive error. A controlled pattern of infra-red radiation is directed through anterior layers of the cornea to be absorbed by collagen tissue within the stroma in order to raise the temperature of one or more portions to a level sufficient to cause those portions to shrink, thus reshaping the anterior corneal surface and changing the optical properties of the cornea. The radiation pattern used depends upon whether myopia (nearsightedness) , hyperopia (farsightedness) or astigmatism is the refractive error being corrected. Several specific techniques have been suggested for delivering the radiation pattern to the cornea. The infra-red radiation may be projected, for example, onto the anterior surface without any contact with that surface, may be projected through a transparent heat sink element placed against the surface, or may be directed through one or more optical fibers at a time to an optical element which contacts the surface. Such techniques are illustrated in Patent Cooperation Treaty application publication numbers WO 91/00063 of Dr. Bruce J. Sand and WO 92/01430 of Dr. Michael Berry.

It is a primary object of the present invention to provide an improved infra-red radiation delivery system of the type utilizing optical fibers and/or a coupler contacting the anterior of the cornea or other portion of the human body which is being treated.

Summary of the Invention Briefly and generally, a transparent coupler is provided with one surface shaped to conform with the anterior surface of the cornea or other body surface in order to closely contact that surface. A plurality of optical fibers are attached to the outside of the coupler in order to transmit infra-red radiation therethrough in a pattern established by the pattern of optical fibers which are illuminated. The optical fibers are preferably illuminated by one or more diode lasers but other types of infra-red radiation sources can alternatively be employed. In a preferred implementation, holes are provided in the coupler from its outside, but not through the body contacting surface, with a pattern which corresponds with a desired pattern of radiation spots to be delivered. Individual optical fibers are then terminated in the individual holes during delivery of the radiation pattern. The pattern of holes is customized for each patient or type of procedure, and is discarded after a single use. Additional objects, features and advantages of the various aspects of the present invention are given in the following description of their preferred embodiments, which description should be taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a schematic cross-sectional view of a device for coupling to the eye while reshaping its cornea.

Figure 2 is a schematic assembly of the platform, articulated arm, coupler device and related equipment used to perform cornea reshaping.

Figure 3 shows an alternative embodiment of a system for corneal reshaping, including a bundle of optical fibers terminating in the coupler of Figure 1. Figure 4 is a view of the eye contacting surface of the coupler of Figure 3, as viewed from a direction of the arrows 4-4 of Figure 3.

Figure 5 shows yet another embodiment of a system for corneal reshaping that uses only a few optical fibers that are detachably connected to a corneal coupler, an inventory of differently shaped couplers being provided for various specific corneal reshaping procedures and patients.

Figure 6 is a view of the corneal coupler of Figure 5, as viewed from position 6-6 of Figure 5.

Figure 7 is a cross-sectional view of the corneal coupler of Figures 5 and 6, taken at section 7-7 of Figure 6. Figure 8 illustrates an alternative embodiment using a bundle of optical fibers to define the corneal exposure pattern, which pattern is then imaged onto the anterior surface of the cornea.

Description of the Preferred Embodiments

Referring to Figure 1, a coupler device is shown in schematic cross section. The primary components of the coupling device 10 are transparent body 11, suction ring 20, corneal engaging surface 30 and an optional mask 40. The cornea itself is identified by the number 50 and the central optic portion of the cornea by the number 60. It is sometimes desirable that the central optic portion 60 of the cornea 50 not be illuminated, so the mask 40 can be employed in such incidences to block incident radiation 70 in this area. The incident light energy 70 is emitted from an appropriate energy source, i.e., a hydrogen fluoride, thulium or holmium doped laser.

The corneal engaging surface 30 of the coupler 10 acts to interface between the coupler device 10 and the cornea 50. The coupler device 10 is maintained in position by suction ring 20 which is sized to encompass a substantial portion of the human cornea. It is anticipated that a film of tears or ophthalmic solution may be found between the coupler device 10 and cornea 50. The coupler device 10 is removably attached to the anterior surface of the cornea.

The central portion 11 of the coupler 10 is made from a transparent material such as Infrasil quartz (a purified form of quartz that is highly transparent to radiation at about 2 microns in wavelength), calcium fluoride, sapphire, diamond, or a fluoro-polymer material such as that available from Fresnel Technologies of Fort Worth, Texas, as "Poly IR5". Other materials that satisfy the functional characteristics of providing a heat sink, template, thermostat, positioner, restrainer and mask can likewise be used. The coupler is used by grasping the suction ring 20 on its outermost edges 21 and pressing the device onto the corneal surface. In this fashion the suction ring acts as both a means for restraining movement of the eye and a means for immobilizing the eye. However, particularly for short exposures, the coupler 10 may be held by hand against the cornea instead of using a suction ring. Since the body 11 is transparent, the operator has the benefit of viewing the eye through the body 11 in order to properly position the coupler 10 with the pupil of the eye 50 substantially centered within the ring 20. In one implementation, the coupler 10 is removably mounted in a stable platform 80 (see Figure 2) to insure that the eye, coupler and light source are maintained in coaxial alignment for the duration of irradiance. The stable platform includes an articulate arm 81. In Figure 2, a schematic representation of the stage assembly 80 with the coupler 10 in place over the eye 50 is shown. Optical connections are conveniently made as part of a beam delivery system (also referred to as light energy source) 70 by fiber optic cable. A control panel is actuated and used by the operator to control a display so that appropriate surgical modification can be made to the eye.

An operator has access to the means for determining the change of shape of the cornea of the eye, in the preferred embodiment a surgical keratometer, and also to the means for viewing the cornea 50 of the patient's eye, in the preferred embodiment an ophthalmic surgical microscope.

The coupler 10 is adapted for use in combination with a noninvasive ophthalmological method for reshaping the anterior surface of the cornea in order to achieve emmetropia (normal vision) . The coupler 10 is positioned over the eye 64 during the reshaping procedure. The coupler 10 is made of a material that is substantially transparent to the light energy being used to reshape the cornea 50. The functions of the coupler 10 include acting as one or more of: (1) a heat sink and thermostat; (2) a template for the cornea; (3) a positioner and restrainer for the eye; and (4) a mask during the reshaping procedure.

The coupler 10 consists of two major functional parts. The first part is an annular suction ring 20 shown in Figure 1. The purpose of the annular suction ring 20 is to attach the coupler to the eye by use of a vacuum. A vacuum of approximately 10 mm. of mercury (Hg) is used. The functions of positioning and restraining the eye 64 are accomplished by attaching the coupler 10 to the eye 64. These functions are achieved because the couplers 10 can be positioned and maintained in place during the procedure; therefore by being attached to the eye 64, the eye 64 will also be positioned and restrained.

The coupler 10 has its substantially transparent center portion 11 with a radially curved surface 30 which approximates the desired emmetropic shape of the anterior portion of the cornea. (Figure 1) This part of the coupler performs the functions of acting as a heat sink and thermostat, and, optionally, a template for the cornea and a mask during the reshaping procedure.

The heat sink and thermostat function is desired as a means of maintaining the epithelium and epithelial basement membrane at a sufficiently cool temperature during treatment in order to prevent clinically significant damage, particularly to the important basement membrane layer. The epithelial basement membrane controls the attachment of epithelial cells to the underlying Bowman's layer of the cornea. It must be protected during the heating of the stro a. The corneal engaging surface 30 of the coupler

10 (Figure 1) has a radius of curvature which approximates the desired emmetropic shape of the cornea to be formed by the reshaping procedure. The corneal engaging surface 30 actually rides on a thin tear film or ophthalmic solution on the surface of the cornea. A thin ophthalmic solution film can be used in conjunction with the coupler to prevent damage to the epithelium.

The masking function of the coupler is optionally performed by blocking all light energy from impacting on any portion of the cornea desired to be protected from any effect of the radiation, such as the central optic zone of the eye. This prevents inadvertent reshaping of any portion of the cornea that is not desired to be treated. The reshaping procedure uses a light source 70 emitting a wavelength or wavelengths with correct optical penetration depths to induce thermal changes in the corneal stromal collagen without damaging the viability of the corneal endothelium or the anterior surface of the corneal tissue and without causing a sufficient wound-healing response to lead to long-term corneal reshaping. The light source is coupled with a light delivery and control means for producing the required radiant exposure time and geometric pattern in order to achieve the desired change in the shape of the cornea. Anterior corneal surface cooling by the coupler is used to prevent damage to the epithelium and epithelial basement membrane.

Another system for delivering a controlled infra-red electromagnetic radiation pattern is described in Patent Cooperation Treaty application publication number WO 94/03134 of David R. Hennings and Ralph W. Olenick. The system there described projects a symmetrical octagonal pattern of spots onto the outside of the cornea, the spots being arranged with equal spacing around a circle having a controllable diameter. Each of the eight spots is individually shuttered so that fewer than all of the spots may be selected for any particular treatment. Of course, some number of symmetrically spaced radiation spots other that 8 spots may be alternatively delivered by a modified apparatus.

It is preferred that a center of this circle be positioned coincident with the center of the pupil of the eye being treated. A pulsed holmium doped YAG laser, emitting radiation with a wavelength of about 2.13 microns, is utilized as the source. Each radiation spot has a diameter of about 600 microns. Treatment is accomplished, according to one specific set of parameters, by exposing the cornea to a series of from 5 to 15 radiation pulses, 10 pulses being used in one application. Each pulse has a duration of about 250 micro-seconds. The pulses are delivered at a rate of about 5 Hz. (about 200 milli-seconds between successive pulses) . The diameter of the circular spot pattern, the number of spots in the pattern being utilized and the amount of energy being delivered are selected to provide correction for different refractive errors. To correct for hyperopia, the cornea is exposed to all eight spots in a circle having a diameter within a range of about 5.5 to 8 mm., 6 mm. being typical, with an energy level of from 15-35 milli-joules (typically 25) being delivered to each spot per pulse. For correction of myopia, the spots are arranged in a circle having a diameter within a range of about 2 to 4 mm., 3.5 mm. being typical. Each of the eight spots is then provided with from 12-25 milli-joules (typically 20) of energy. Alternatively, the cornea can be exposed in its center, for myopia correction, to a single spot or pattern of spots to produce corneal flattening to some predetermined shape.

In the case of correcting for regular astigmatism, only 4 spots of the larger (5.5 to 8 mm.) are used in two opposing quandrants (the other 4 spots being blocked), with the pattern being rotated to position the spots symmetrically with the flattest meridian of the cornea's outside surface. This treatment will remove a cylindrical error of refraction from the eye. Other patterns are used to correct for irregular astigmatism. It is preferred, with patients having both spherical errors (hyperopia or myopia) and astigmatism, to first correct the eye for the astigmatism and then expose it again to the complete pattern in order to correct for the spherical error. The parameter ranges given in the immediately preceding paragraph have been used with the system of aforementioned Patent Cooperation Treaty application publication number WO 94/03134 without the use of a contact lens or other heat removal material in contact with the cornea. The spot pattern is projected onto the cornea without contact with the cornea. When a contact lens is used, the energy levels given above are increased by a few percent to compensate for Fresnel losses at surfaces of the contact lens through which the radiation pattern passes. In either case, the purpose of the treatment is to raise the temperature within volumes of the stroma positioned behind the radiation pattern to within a range of 58-75 degrees Celsius. Collagen tissue within such volumes thus shrinks and causes the outside surface of the cornea to be reshaped. Referring to Figures 3 and 4, an optical fiber bundle 101 has one end thereof attached to the surface 40 of the coupler 10 described above with respect to Figure 1. As shown in Figure 4, ends of the optical fibers of the bundle 101 are viewable through the coupler in a region inside of the vacuum ring. The illumination pattern across the cornea in contact with the coupler surface 30 is determined by directing the infra-red electromagnetic radiation along selected ones of the optical fibers from a diode laser array 103. That is, rather than scanning the fiberoptic array with a single diode laser, which is one way it has been done, a separate diode laser is coupled within the array 103 to each of the optical fibers within the bundle 101 at an end opposite of that to which the coupler 10 is attached. An electrical power supply circuit 105 individually provides a controlled amount of power to the selected diode lasers within the array 103 by interconnection over separate circuits 107. A microprocessor based controller 109 controls, through an interconnecting bus 111, which of the diode lasers in the array 103 are to be energized by the power supply 105. A user interface 113, preferably including a keyboard and monitor, allow the operator to configure the system for a particular corneal reshaping procedure by setting parameters within the controller 109. The controller 109 also controls a vacuum pump 115 that is mechanically connected to the vacuum port 21 of the coupler 10. The coupler 20 may be made to be removable from the fiber bundle 101, or the fiber bundle 101 may be made to be removable from the diode laser array 103, if desired. Either or both of the coupler 20 and the fiber bundle 101 may be made disposable.

The output frequency of radiation from commercially available diode lasers is dependent upon both their composition and operating temperature. Thus, it is desirable to control the temperature of the diode laser array 103, a temperature control circuit 117 being provided under the control of the controller 109 over a bus 119. Available diode lasers also exhibit a greater output power at lower temperatures, so cooling them is usually desirable. Optimally, each of the diode lasers within the array 103 is provided with its own individual cooling device that is separately controlled by a signal on one of a plurality of circuits 121 from the temperature control circuitry 117. Individual solid state thermo-electric coolers are preferably mounted as part of each diode laser within the array 103. The temperature of each diode laser is measured by a thermistor or thermocouple attached to the individual diode lasers within the array 103. Temperature signals are communicated to the temperature control circuitry 117 over circuits 121. A particular advantage of individually controlling the temperature of each diode laser within the array 103 is that the output wavelength can be controlled over a small range by setting, through the controller 109, the desired operating temperature of each of the diode lasers. This wavelength control allows compensation for wavelength differences caused by variations in composition of the materials forming each of the diode lasers. Further, it allows selecting, to some extent, the corneal absorption coefficient by selecting the wavelength at which each energized diode laser operates. That is, the temperature to which a volume of the cornea is raised by exposure to a given infra-red radiation spot can be controlled over at least a limited range by controlling the temperature of the diode laser generating that radiation spot. This allows the energy level of all the spots to be controlled to be the same, or, alternatively, to intentionally be made different in order to individually control the temperature profile through the thickness of the stroma at the location of each radiation spot. Very sophisticated corneal recurvature operations can be accomplished by such a method.

At the time of filing the present patent application, diode lasers having a sufficient power for this application are costly, thus making the implementation described with respect to Figures 3 and 4 very expensive. The complete flexibility provided by the system of Figures 3 and 4 comes at some substantial cost. Therefore, an alternative system embodiment shown in Figures 5, 6 and 7 utilizes a corneal coupler 125 of a different design and only few diode lasers, such as lasers 127, 129 and 131, as required to generate the separate number of spots. The individual spots may be circular or some other controlled shape. In the example system of Figures 5-7, eight such spots, and thus eight such diode lasers are employed. Each diode laser is coupled into one end of an optical fiber, such as the respective optical fibers 133, 135 and 137. Each of the diode lasers has one of respective thermo-electric coolers 139, 141 and 143 attached. Similarly, each of the diode lasers has one of respective thermistors or other temperature measuring devices 145, 147 and 149 attached. A temperature control circuit 151 receives the individual temperature dependent electrical signals from the diode laser thermistors, and generates a controlling electrical signal to the individual coolers in order to maintain the individual diode lasers at desired temperatures.

This thus allows a closed loop temperature control of each of the diode lasers in the system. A power control circuit 153 individually provides the correct amount of current to each of the diode lasers 127, 129 and 131. This power is set by a system controller 155. The system controller 155 also controls the temperature control circuitry 151 in order to operate the individual diode lasers at temperatures which provide the desired individual infrared radiation wavelength. A user interface 157, usually including a monitor and keyboard, allows the operator to program the system controller 155 for the desired temperature and input power to each of the diode lasers. Of course, some of the lasers will not be energized at all where a number of spots to be generated is fewer than the number of diode lasers in the system. The system controller 155 also controls a vacuum pump 159 that is connected to the coupler 125 through a vacuum line 161. Rather than each of the optical fibers 133,

135, 137, etc., being fixedly attached to the coupler 125, each of the diode laser illuminated fibers in the system is removably attached to a backside of the coupler 125 in a manner shown best in the views of Figures 6 and 7. This allows easy replacement of the coupler without having to make any other physical changes to the rest of the system shown in Figure 5. Alternatively, but not preferably, the optical fibers can be permanently attached to the coupler and a multi- fiber connector provided for disconnecting the coupler/fibers from the rest of the system in order to replace it. In either case, the coupler can be made to be a disposable item.

The coupler 125 is formed of two primary components. A first component is a transparent heat sink element 163 that has a concave surface 165 shaped to contact an anterior surface of a cornea being treated. A circular groove 167 is provided around the outside edge of the surface 165 in order to hold the coupler 125 against the cornea being treated when a vacuum is applied to the groove 167. A plurality of ports spaced around the element 163 could alternatively be provided. The groove 167, or such ports, are coupled with the vacuum line 161. However, some ophthalmologists and other operators may prefer not to use such a vacuum attachment system but rather will simply hold the coupler 125 by hand against the eye during the radiation exposure. Application of sufficient pressure between the surface 165 and the eye prevents movement of the eye during the short period of treatment.

The material of the element 163 is preferably made of the aforementioned Poly IR5 fluoro-polymer material or Infrasil quartz. Its thickness is preferably substantially uniform. These materials have thermal transfer properties sufficient to carry heat away from the anterior surface of a cornea to which it is attached in order to provide the temperature profile through the cornea thickness that has been described earlier. These materials are also sufficiently non- absorptive of infra-red radiation treatment wavelengths of around two microns that radiation loss and a resulting heating of the element 163 is avoided. The preferred materials are also substantially transparent to visible radiation wavelengths.

Attached to an outer curved surface of the first element 163 is a second element 169 having a complementary shape at a surface that adjoins and is fixed to the outer surface of the contact lens element 163. A primary purpose of the element 169 is to provide properly positioned receptacles for each of the optical fibers that are to be connected to it for the delivery of energy to the cornea. Alternative devices and structures could instead be provided on the backside of the element 163 to position and hold the optical fiber ends in desired spaced apart pattern but what is shown in Figures 5-7 is preferred. A circular pattern of eight fiber receiving receptacles is best shown in the backside view of Figure 6, including passages 171 and 173 that are also shown in a cross sectional view of Figure 7. The pattern of passages is formed to correspond with the radiation pattern to which the cornea is desired to be exposed. In the example of Figures 5-7, eight such passages are equally spaced around a circle having a center 175, similar to the patterns previously described to be generated with the non-contact system of aforementioned Patent Cooperation Treaty application publication number WO 94/03134. Other parameters, however, are likely to be different, as described below.

As illustrated in Figure 7, each of the optical fibers removably connected with the coupler 125 has a coupler attached to its free end. For example, the optical fiber 133 is terminated in a circularly shaped sleeve 177. The fiber 133 with its outer sheath attached is firmly fit within an opening interior of the sleeve 177. An enlarged diameter portion of the sleeve 177 is provided for ease in gripping by hand. A second sleeve 179 is attached around the outside of the optical fiber 133 along a distance removed somewhat from its end. The sleeve 177 extends over the second sleeve 179 for a distance to provide the enlarged diameter portion for gripping. The second sleeve 179 also provides additional support and stiffening of the optical fiber 133 for a distance adjacent to its end. A portion 181 of the optical fiber, with sheath removed, is exposed in the interior passageway of the sleeve 177. An end of the fiber tip 181 is maintained a controlled distance inward of an extreme end 182 of the sleeve 177, which extreme end 182 abuts against the outer surface of the contact lens element 163. Since the infra-red energy exits the end 181 of the optical fiber in a spreading cone, this distance significantly affects the size of the resulting spot which is illuminated on the cornea surface. It is most convenient when this distance be made to be the same for each of the optical fiber ends. Since the optical path length from each of the optical fiber ends to the cornea surface is made to be substantially the same, the size of each spot is thus substantially the same.

The system is preferably calibrated to make the size, energy distribution and total energy of each spot substantially the same. Of course, the infra-red radiation spots can intentionally be made to have any of these aspects different from one-another, if desired for some reason. For example, the spot sizes can be made to have different sizes by simply providing different distances between the ends of the optical fibers and the open ends of their respective sleeves. However, use of the system then becomes somewhat more involved.

Each of the optical fiber free ends fitted with the structure described for that of the optical fiber 133 can be held within the second optical element 169 in any one of a number of different ways. The simplest way is to size the mating element portions so that a tight frictional fit is obtained upon hand insertion of the fiber tip sleeve into the receiving aperture of the element 169. If more positive control is required, a set screw (not shown) can be added for each of the optical fibers in individual holes extending inward from a side edge of the element 169. Alternatively, available latching mechanisms can be adapted for the small size of the optical fiber sleeves and receiving apertures. Since the treatment radiation does not pass through the second element 169, its properties with respect to infra-red radiation are not important. But it is important that the element 169 be substantially transparent to visible wavelengths so that the operator may properly position it on the patient's cornea before affixing it to the cornea by applying vacuum to the vacuum line 169. The material of the element 169 should also be easy to work in order to form it into the shape with apertures as described. Commercially available plexiglass is among satisfactory materials for this purpose.

It is preferred, as shown in Figure 7, that the fibers be oriented substantially perpendicularly with the surface 165, and thus also with the similarly shaped anterior surface of the cornea being treated. This results in a central ray of cone shaped infra-red energy exiting an end of the individual optical fibers striking the cornea perpendicularly. Another way to express this geometry is that a longitudinal axis of each of the apertures in the element 169, and thus of each of the optical fibers inserted therein, passes through a center of curvature of the surface 165 in a region opposite to an inner end of the aperture and termination of the fiber positioned therein.

An advantage of the treatment system of Figures 5-7 is that many versions of the coupler 125 may be kept on hand and easily interchanged. Different versions can be provided for different treatments. For example, the apertures may be positioned in a circle of different diameters in two different couplers, about 6 mm. for effecting correction of hyperopia and about 3.5 mm. for correction of myopia. If only spherical correction is to be effected, optical fibers are then inserted into each of the 8 apertures and energized. If cylindrical correction is to be accomplished, optical fibers need be inserted only into the 4 apertures of two opposing quadrants and then energized, the remaining apertures being unfilled. More complicated astigmatic correction may require yet a different pattern of apertures. Even some spherical correction treatments may desirably be performed with a coupler having optical fiber receiving apertures arranged in two circles of different diameters. In all these cases, the operator can see through the coupler element 125 in order to line up the center 175 of the coupler with a center of the pupil of the eye being treated. Some treatments may benefit from a two or more exposures though all connected fibers with the coupler rotated about its center 175 in between exposures after the vacuum is released.

For the convenience of the operator, the element 169 may have an alignment pattern inscribed on one of its surfaces. A series of concentric circles makes it easier to center the coupler with the pupil of the eye being treated. A series of lines or other marks across the coupler at various angles through the center 175 makes it easier to orient the coupler by rotation when a non-spherical correction, such as for astigmatism, is being made.

In all cases described herein of a coupler being attached to a corneal anterior surface, a tear layer will almost always be interposed therebetween. It is desirable, however, to minimize the thickness of any tear layer, at least in the regions through which radiation passes. This is in order to minimize the amount of radiation absorption by any such layer since such absorption reduces the amount of energy that remains available to heat the stromal collagen. However, it is generally desired to minimize such a layer which is accomplished by shaping the corneal contacting surface 165 of the coupler as closely as possible to the outside surface of the eye being treated. In the embodiments described above, the cornea is exposed to a pattern of circular spots. It is certainly possible, of course, to expose the cornea to lines, arcs, or other radiation patterns other than simple circular spots. The embodiment of Figures 3 and 4, for example, can form such other shapes from a plurality of contiguous dots formed from exposing a selected pattern of a plurality of contiguous optical fibers to the infrared treatment radiation. In the embodiment of Figures 5-7, optical elements can be formed at the ends of each of the optical fibers in order to project onto the cornea some shape other than a round spot. Further, a number of fibers can be positioned adjacent to one another in the embodiment of Figures 5-7 in order to form other radiation patterns. The preferred diode laser for use in the embodiments described above is an indium-gallium- arsenide-phosphide (InGaAsP) type formed in a strained layer with a double quantum well. Such a diode laser, commercially available from Applied Optronics Corp. of South Plainfield, New Jersey, is selected to emit electromagnetic radiation within a range of about 1.9 to 2.1 microns, depending upon the specific composition and operating temperature. Within this range, a wavelength of about 1.95 microns corresponds to the maximum absorption by the stromal tissue which is patterned after that of water, while a wavelength of about 2.1 microns corresponds to the minimum tissue absorption within the diode laser's available range of wavelengths. The difference in absorption is a factor of about 4. Thus, there is a considerable amount of control available over the radiation absorption characteristics by selection of the composition of the diode laser and by controlling its operating temperature, thus to control the thermal profile through the thickness of the stroma in exposed areas.

Such diode lasers are preferably operated by applying a single pulse of radiation lasting from 200 to 400 milliseconds. When operating at about 1.95 microns, the energy applied is preferably within a range of from 15 to 35 milli-joules per approximately 600 micron diameter spot, 25 milli-joules being typical. At this wavelength, only about one tenth of the total energy is required as compared with the pulsed holmium laser embodiment described previously. This is because of the different wavelengths used and delivery of the radiation in a single pulse rather than a series of repetitive pulses. When operating at about 2.1 microns, approximately four times the amount of energy is required. Either way, heat affected zones within the stroma are raised to within the treatment range of from 58 to 75 degrees Celsius in order to effect corneal recurvature. Such zones will be deeper into the stroma when the less absorptive wavelengths are used.

By use of a separately controlled diode laser to generate each spot or other shaped area to which the cornea is exposed, the duration of the exposure pulse forming each exposed area may be individually controlled in addition to controlling the degree to which the radiation is absorbed by the corneal tissue through adjustments of its wavelength. This flexibility is particularly advantageous for correction of non- spherical refractive errors, such as astigmatism.

Although the examples of tissue shrinkage given above relate specifically to refractive error correction of the eye, very similar procedures, couplers and systems can be employed to shrink or otherwise treat tissue in other regions of the human body. In any such treatment, the surface of the coupler contacting a surface of the body, either an external or an internal surface, is shaped to closely conform to the shape of such a surface in order to provide maximum coupling of the infra-red treatment radiation. The infra-red radiation patterns, specific wavelength(s) , energy applied, manner of applying the energy, and other parameters, are selected consistent with the particular tissue treatment.

The selective energization or positioning of optical fibers to generate desired radiation patterns is not limited to use of a contact coupler. An example of non-contact treatment is given in Figure 8. A plurality of optical fibers 201 form a desired infra-red radiation pattern at a surface 203 that is imaged by an appropriate optical system onto a surface 207 of a cornea or other body portion to be treated. The plurality of fibers 201 can be a complete bundle, such as the bundle 101 (Figures 3 and 4), wherein those fibers creating the desired pattern in the surface 203 are illuminated from their opposite ends. A diode laser may be connected to illuminate each fiber when energized, or one diode laser may be scanned across the bundle of fibers to illuminate a selected few. Alternatively, the plurality of fibers 201 can be a few fibers whose ends are positioned into the desired pattern, as done in the embodiment of Figures 5-7. Although the present invention has been described with respect to its preferred embodiments, it will be understood that the invention is entitled to protection within the scope of the appended claims.

Claims

It is Claimed:

1. A system for internally heating human tissue by exposing an outside surface of a given shape to a predetermined pattern of infra-red radiation, comprising: a coupler having on one side thereof a first surface with a shape that is complementary to said given outside surface shape and a second surface on an opposite side thereof, said coupler having a plurality of apertures extending into and spaced apart across said second surface, said apertures having ends internal of the coupler a distance from said first surface and arranged in said predetermined radiation pattern across said first surface, at least regions of said coupler between said internal ends of the plurality of apertures and said first surface being substantially transparent to said infra-red radiation, a source of said infra-red radiation, and a plurality of optical fibers having first and second ends, said first ends being coupled to receive infra-red radiation from said source and said second ends being removably inserted into unique ones of said plurality of apertures, thereby to direct radiation therefrom through said first coupler surface in said predetermined pattern.

2. The system of claim 1 wherein said coupler includes a first element including said first surface and a second element including said second surface, said first and second elements being attached to each other along a third surface that is intermediate of said first and second surfaces, said plurality of apertures extending completely through the second element but not into the first element, thereby locating said aperture ends at said third surface.

3. The system of claim 2 wherein said first element has the same thickness in at least regions opposite said aperture ends.

4. The system of claim 2 wherein said first element includes a material within a group consisting of quartz, calcium fluoride, sapphire, diamond and a fluoro-polymer.

5. The system of claim 2 wherein each of at least some of said second optical fiber ends have a hollow sleeve attached with one end thereof remaining open and positioned a certain distance removed from said optical fiber end.

6. The system of claim 2 wherein each of said first and second elements is characterized by being transparent to visible electromagnetic radiation.

7. The system of claim 1 wherein individual ones of said plurality of apertures are oriented with a longitudinal axis extending orthogonally to said first surface at a point of intersection therewith.

8. The system of claim 7 wherein said optical fiber second ends are positioned a fixed distance from said second surface and the material of the element therebetween is the same.

9. The system of claim 1 wherein said first surface is a concave shape.

10. The system of claim 1 wherein said apertures are arranged in a circle across said second surface.

11. The system of claim 1 which additionally comprises a vacuum pump and wherein said coupler includes an opening in said first surface that is operably coupled to said vacuum pump.

12. A system for internally heating human tissue by exposing an outside surface of a given shape to one of at least first and second predetermined patterns of infra-red radiation, comprising: at least first and second radiation couplers that each have on one side thereof a first surface with a shape that is complementary to said given outside surface shape and a second surface on an opposite side thereof, each of said at least first and second couplers having a plurality of apertures spaced apart across said second surface and extending into said second surface to closed ends within the coupler a distance from said first surface, at least regions of each of said at least first and second couplers between said closed ends of the plurality of apertures and said first surface being substantially transparent to said infra-red radiation, said first coupler having its said aperture ends arranged across said first surface in said first predetermined pattern, and said second coupler having its said aperture ends arranged across said first surface in said second predetermined pattern, a source of said infra-red radiation, and a plurality of optical fibers having first and second ends, said first ends being coupled to receive infra-red radiation from said source and said second ends having individual sleeves attached thereto which are shaped to mate with at least one aperture of each of said at least first and second couplers, thereby to allow at least one of said second optical fiber ends to be removably inserted into at least one of the apertures of each of said first or second couplers.

13. The system of claim 12 wherein each of said first and second couplers comprise a first element including said first surface and a second element including said second surface, said first and second elements being attached to each other along a third surface that is intermediate of said first and second surfaces, said plurality of apertures extending completely through the second element but not into the first element, thereby locating said aperture ends at said third surface.

14. The system of claim 13 wherein at least regions within the first element that are located opposite said aperture ends are transparent to said infra-red radiation and are of the same thickness, and further wherein at least some of said second optical fiber ends have a hollow sleeve attached with one end thereof remaining open and positioned a certain distance removed beyond said optical fiber end.

15. An infra-red radiation coupler, comprising: a first element including a region that is transparent to both visible and infra-red radiation, said region having the same thickness between a first surface of concave shape and a second surface of convex shape, a second element including a region that is transparent to visible radiation, said region having a first surface of concave shape that matches the second convex surface of the first element and is attached thereto, said region also having a second surface on a side of the second element opposite to the first surface, and a plurality of apertures extending completely through said second element between said first and second surfaces thereof, said apertures being oriented with longitudinal axes thereof being perpendicular to the first surface of second element.

16. A method of altering refractive properties of a cornea by exposing the cornea to a predetermined pattern of infra-red radiation, comprising the steps of: positioning tightly against an outer surface of the cornea a first surface of a heat conductive element that is transparent to both visible and infra¬ red radiation, attaching to a second surface of the heat conductive element opposite said first surface a plurality of optical fiber ends that are spaced apart from one another and arranged in a pattern across the second surface of the heat conductive element that corresponds to said predetermined radiation pattern, and directing infra-red radiation through the optical fibers to exit said ends, thereby to expose the cornea to said predetermined pattern of infra-red radiation.