INSTRUMENT FOR OPHTHALMOLOGICAL SURGERY

Abstract: The surgical instrument apparatus emits a narrow beam of light (240) that exits a point (201) on the blade (100). The light (240) crosses in front of the blade at a point predetermined by the surgeon. The light (240) is reflected off the Descemet's membrane (203) when the tip of the blade (100) reaches the proper depth and bounces back into an entrance point (202) on the blade (100). The reflected light is received by a light sensor (220) that is coupled to a transmitter (222). The transmitter (222) sends a signal to a receiver (243) coupled to a tone generator (251). When the tone is generated, the surgeon knows that the incision has reached the proper depth.

Description: INSTRUMENT FOR OPHTHALMOLOGICAL SURGERY Field of the Invention The present invention relates generally to the field of surgery and particularly to ophthalmological surgery. Background of the Invention The field of ophthalmological surgery has made great strides in the last few decades. Prior to the 1970's, for example, a patient suffering from myopia could typically only be treated by using corrective lenses such as glasses or contact lenses. Now, surgical techniques such as photorefractive keratecomy, keratomileusis, and radial keratotomy, also known as RK, can reduce or completely cure a patient's myopia. RK has enjoyed the greatest growth over the past few years. This procedure is most effective on a patient requiring less than six diopters of correction. RK is performed by making four to sixteen incisions in the cornea in a spoke pattern from a central hub of untouched tissue. The number of incisions and the length and depth of each incision depends on the degree of correction that particular eye requires. A severely myopic eye would need longer and deeper incisions than a less myopic eye. The severely myopic eye would also require more incisions. The incisions increase the surface area of the eyeball thus allowing the internal pressure of the eye to flatten the central portion of the cornea. The flattening refocuses the light entering the eye onto the retina instead of in front of it as in a myopic eye. The RK procedure begins with a mapping of the thickness of the cornea using an ultrasound device, a procedure that is known as pachymetry. The measurements resulting from the pachymetry have an accuracy of ±1 micron. These measurements inform the surgeon on how deep the incisions can be made without perforating the cornea and entering the anterior chamber. The surgeon then makes temporary impressions into the anesthetized eye. The impressions show where to make the incisions and where to begin and end the incising. The incising is performed by an instrument that is comprised of a blade extending through two footplates, a barrel encompasses the blade, and a micrometer on the end opposite the blade. The footplates rest on the eye while the blade is cutting. The micrometer is adjusted by the surgeon to extend or retract the blade from the end of the instrument by a predetermined amount depending on the depth of the incision required. To achieve greater accuracy than using the micrometer alone, the blade length can be measured under the operating microscope using a scale having various depth graduations. The surgeon places the blade adjacent the depth needed on the scale and adjusts the micrometer portion of the instrument until the blade reaches that particular number. This measurement procedure has an accuracy of ± 3 microns. While incising the eye, the surgeon must maintain the depth of the incision to within 80 - 90% of the corneal thickness; the typical corneal thickness being 0.55 millimeter. If an incision with improper depth is made, the eye will not heal with the proper correction. Since the eye has a varying thickness, which is indicated by the pachymetry procedure, the surgeon may have to change the length of the blade for each incision to maintain the proper depth. At the same time, the RK procedure must be accomplished as quickly as possible to prevent the eye from dehydrating, thus causing the corneal thickness to change from the previously measured thicknesses. Stopping to adjust the depth of the blade slows the pace of the operation. There is a resulting need for an instrument that allows real-time feed-back to the surgeon on the depth of the blade. Summary of the Invention The apparatus of the present invention encompasses a surgical instrument that has a blade for cutting tissue, the tissue being corneal tissue in the preferred embodiment. The apparatus is comprised of a light source that generates light to be reflected off the tissue. The reflected light is accepted by light receiving means. Alert means, that is coupled to the light receiving means, signals receipt of the reflected light. The generation of the alert signal indicates the proper depth to the surgeon. Brief Description of the Drawings FIG. 1 shows the surgical instrument of the present invention. FIG. 2 shows a magnified view of the blade in association with the eye tissue to be incised. Detailed Description of the Preferred Embodiment The surgical instrument apparatus of the present invention provides real-time feed-back to the surgeon on the depth of the incision being made. By focusing a narrow beam of light at a predetermined distance from the tip of the blade and receiving the light reflected off the Descemet's membrane of the eye, an alert tone informs the surgeon when the necessary depth has been achieved. The apparatus of the present invention is illustrated in FIG. 1. The apparatus, in the preferred embodiment, has a diamond blade 100. Manufacturing the blade from diamond not only allows it to be made only 150 microns thick while retaining high strength, but the optical properties of the diamond are such that light is transmitted through the blade 100. The blade extends through two footplates 101 and 102 on either side of the blade 100. These footplates 101 and 102 rest on the eye as the surgeon is cutting. A barrel 103 encompasses the blade 100 and provides a surface for the surgeon to hold. A micrometer 104 is coupled to the end of the apparatus opposite the blade 100 end and extends or retracts the blade 100 depending on the direction the micrometer is turned. Also at this end, illustrated in FIG. 2 and housed within the apparatus, is a means for generating a narrow light beam 210, a light sensor 220, light detection circuitry 230, and an infra-red light transmitter 222. The light sensor 220, detection circuitry 230, and transmitter 222 are well known in the electronics art and, therefore, will not be discussed indepth. In the preferred embodiment, the narrow light beam 240 is generated by a laser 210. This light 240 is transmitted the length of the blade 100 and exits a notch 201 on one side of the blade. The narrow light beam 240 is angled such that it crosses, at a predetermined distance of 50 microns, a centerline 241 extending through the tip of the blade 100. In the preferred embodiment, the light beam 240 is redirected to intercept the centerline 241 by the angle that the notch is cut. In an alternate embodiment, the proper angle to intercept the centerline 241 is achieved by the placement of the laser 210 within the instrument. As the surgeon applies pressure to the apparatus, thus causing the blade 100 to incise deeper into the corneal tissue 200, the light eventually strikes the shiny surface of the Descemet's membrane 203. The light striking 242 this surface signals the proper depth of the incision. The light is reflected off the membrane 203 and back into the blade 100 through another notch 202 cut into the blade 100 opposite the light exit point 201. This light entrance notch 202 is formed such that the narrow beam of entering light is transmitted up the length of the blade 100. The light sensor 220 in the micrometer end 104 of the apparatus receives the light. This sensor 220, in combination with the light detection circuitry 230, transforms the light energy into a current that is detected by the transmitter 222. In the preferred embodiment, the transmitter 222 transforms the current into an infra-red signal for transmission to an infra-red receiver 243 mounted in headphones 250 worn by the surgeon. Tone generation circuitry 251 is contained in the headphones 250 to emit a tone to inform the surgeon that the proper depth has been achieved. An alternate embodiment uses radio frequencies instead of the infra-red to transmit the correct depth reached signal. Another embodiment mounts the tone generation circuitry on the apparatus to generate an alert that is heard without the use of headphones. Yet another embodiment of the present invention would mount the laser on one of the footplates, angled such that the light beam intersects the centerline. The light sensor is mounted on the opposing footplate to receive the reflected light beam. If, in an alternate embodiment, a blade is used that does not have light conducting properties, such as stainless steel, a light conducting coating can be applied to each side of the blade. The coating would end just above the tip of the blade, thus forming a light exit point on one side and a light entrance point on the other. The laser would then be positioned at the other end of one of the coatings to transmit the narrow light beam the length of the coating and out the light exit point. The other coating would then receive the reflected light and transmit it back to the light sensor. Using the surgical apparatus of the present invention, a surgeon can cut corneal tissue to the proper depth without constantly measuring the length of the blade. By reflecting light off the Descemet's membrane at a distance from the tip of the blade to assure proper incision depth, the surgeon has real-time feed-back on the depth of the incision.

Claims: Claims 1. A surgical instrument, comprising: (a) a blade means for cutting tissue, the blade means having a blade tip and a centerline extending through the blade tip; (b) a light source that emits light such that the light intercepts the centerline; (c) a light sensor for receiving light reflected from light reflecting tissue; and (d) an alert generator, operatively coupled to the light sensor, for signaling receipt of the reflected light. 2. The surgical instrument of claim 1 wherein the blade means is configured to cut a first tissue to a depth such that a light reflecting second tissue is substantially exposed. 3. The surgical instrument of claim 1 wherein the blade means is configured to cut corneal tissue. 4. The surgical instrument of claim 1 wherein: (a) the blade means comprises a light conducting blade having a first side and a second side, the blade comprising a light exit point located on the first side of the blade and a light entrance point located on the second side of the blade; (b) the light is substantially aligned with the light exit point such that light from the light source exits the light exit point; and (c) the light sensor is substantially aligned with the light entrance point such that light which exits the light exit point and is reflected by the reflecting tissue may enter the light entrance point and contact the light sensor. 5. The surgical instrument of claim 4 wherein the light exit point and the light entrance point each comprise a notch in the blade, the light exit point being angled such that the light exiting the light exit point intercepts the centerline extending through the blade tip. 6. The surgical instrument of claim 1 wherein the light source comprises a laser. 7. The surgical instrument of claim 1 : (a) wherein the light sensor comprises depth sensing means for generating a depth reached signal in response to the received reflected light; and (b) the alert generator comprises means for generating a tone in response to the depth reached signal. 8. The surgical instrument of claim 1 : (a) wherein the alert generator is operatively coupled to the light sensor through a communication link; (b) further comprising a transmitter, operatively coupled to the light sensor, for transmitting the depth reached signal via the communication link; and (c) further comprising a receiver for receiving the depth reached signal via the communication link. The surgical instrument of claim 8 wherein the communication link is selected from the group consisting of: an infra-red light link, a radio frequency link, and a wireline link.

Inventors: EPSTEIN ROBERT L, EPSTEIN, ROBERT, L.
Applicants: EPSTEIN ROBERT L, EPSTEIN, ROBERT, L.
Application year: 1993
Main classification: A61B17
IPC codes: A61B17, A61F9