Method and apparatus for precision laser surgery

Abstract

A system for effecting precision laser surgery includes an intensified surgical video microscope directed at the tissue to be operated upon and having zoom capability. The surgical microscope presents a microscopic image on a video screen in front of the surgeon. Preferably, the video screen is divided into multiple separate sections, with the microscopic video image in one section and precise cross sectional and plan views indicating location presented in the other sections of the screen. These additional views may be generated using Moire interferometry by projecting a Ronchi ruling on the surface of the tissue, in viewing the projection with a camera to obtain all necessary information for contour tracking of the subject surface. Interior elements and interfaces of, for example, the eye are also sensed by a light beam and precisely located and mapped by a computer forming a part of the device. The imaging system of the invention enables the surgeon to have before him abundant...

Patent number: 5098426
Filing date: Feb 6, 1989
Issue date: Mar 24, 1992
Inventors: H. Alfred Sklar, Alan M. Frank, Olga M. Ferrer, Charles F. McMillan, Stewart A. Brown, Fred Rienecker, Paul Harriss, Steven Schiffer
Assignee: Phoenix Laser Systems, Inc.

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What is claimed is:

1. A system for use in ophthalmic diagnosis and analysis and for support of ophthalmic surgery, comprising,

three dimensional mapping means for sensing locations, shapes and features on and in a patient's eye in three dimensions, and for generating data and signals representing such locations, shapes and features,

display means receiving signals from the three dimensional mapping means, for presenting to a user images representative of said locations, shapes and features of the eye, at targeted locations including display control means for enabling a user to select the target location and to display a cross section of portions of the eye,

position analysis means associated with and receiving signals from the three dimensional mapping means, for recognizing the occurrence of changes of position of features of the eye,

target tracking means associated with the position analysis means, for searching for a feature of target tissue and finding said features new position after such a change of position, and for generating a signal indicative of the new position, and

tracking positioning means for receiving said signal from the target tracking means and for executing a change in the aim of the three dimensional mapping means to the new position of said feature of the target tissue, to thereby follow the feature and stabilize the images on the display means.

2. The system of claim 1, wherein the display means is a video display, and further including surgical microscope means directed at the patient's eye, for taking video microscopic images of target areas of the ocular tissue and for feeding video image information to the video display means to cause such video microscopic images to be displayed, assisting the user in diagnosis and analysis.

3. The system of claim 1, further including display control means for enabling the user to cause to be displayed on the display means different cross sections of the patient's tissue, as selected by the user.

4. The system of claim 1, wherein the tracking positioning means includes a turning mirror under automatic control, and the system including an objective lens assembly associated with the mapping means and having a final focussing lens, with the turning mirror positioned within the objective lens assembly and movable with respect to the final focussing lens.

5. An instrument and system for high precision ophthalmic laser surgery at a surgical site, comprising,

a laser pulsed source for producing a visible light laser beam having a power capable of effecting a desired type of surgery in an eye,

laser firing control means for enabling a surgeon/user to control the aim, depth, and timing of the firing of the laser to effect the desired surgery,

three dimensional mapping means directed at a patient's eye, for obtaining data representing the location and shapes of features on and inside the eye,

microprocessor means for receiving data from the three dimensional mapping means and for converting the data to a format presentable on a screen and useful to the surgeon/user in precisely locating features of the eye and the aim and depth of the laser beam within those features, and

display means for displaying microprocessor-generated images representing the topography of the eye and the aim and depth of the laser beam before the next pulse of the laser is fired to the surgeon/user in preparation for and during surgery, with display control means for enabling the surgeon/user to select areas of the eye for display, including images of cross sections of portions of the eye.

6. The instrument and system of claim 5, wherein the display means comprises a single video screen divided into multiple displays.

7. The instrument and system of claim 5, wherein the three dimensional mapping means, the microprocessor means, and the display means include means for presenting images to the surgeon/user indicating precise current location of laser aim and depth in computer generated views which comprise generally a plan view and selected cross sectional views of the eye representing features of the eye at different depths.

8. The instrument and system of claim 5, including an optical path with a focusing lens capable of controlling the focus of the laser beam on the eye tissue, and thus the depth at which the laser beam is effective, within about 5 microns, with depth control means for the surgeon to vary the focus of said lens to control the depth at which the laser beam is effective.

9. The instrument and system of claim 8, including system program means enabling the surgeon/user to pre-program a pattern of lesions in the ocular tissue along three axes in three dimensions and to activate the laser to follow the preselected pre-programmed path of surgery automatically.

10. The instrument and system of claim 5, further including tracking means for following movements of the eye during surgery and for following the movement of features at the surgical site of the eye with the three dimensional mapping means and with the laser, including means associated with the microprocessor for recognizing features at the surgical site after said features have moved and redirecting the three dimensional mapping system and the laser to the new location of said features.

11. The instrument and system of claim 10, wherein the display means includes a video monitor which has a frame rate and wherein the tracking means has the capability of following the features, identifying a new location of those features and re-presenting images of those features to the surgeon/user in a time period less than the frame rate of the video display means.

12. The instrument and system of claim 10, wherein the tracking means includes electromagnetically driven turning mirror means along an optical path of both the three dimensional mapping means and the laser beam, for shifting the aim of the three dimensional mapping means and a laser beam in response to the recognized to the recognized shift in position of the features of the eye.

13. The instrument and system of claim 10, wherein the display means comprises a video monitor which as a frame rate and the tracking means includes fast tracking means and backup slow tracking means with the backup slow tracking means including means for following the features at the surgical site, identifying a new location of said features and re-presenting images of said features to the surgeon/user in a time period at least as fast as the video frame rate, and the fast tracking means being capable of tracking movement of the tissue at much faster closed loop response times; and the backup slow tracking means having means for analyzing tissue position based on the three-dimensional topography of the tissue as determined, and for searching and finding, using the microprocessor means, a feature of the tissue when that feature is not found by the fast tracking means and for moving to the new position of the subject tissue feature and enabling the fast tracking means tore-commence fast tracking.

14. The instrument and system of claim 5, wherein the display means comprises a video display monitor, and further including surgical microscope means on a common optical path with the laser beam, for obtaining a greatly enlarged image of a small region of the eye at which the laser beam is directed and for generating a video image of that small region for presentation on the display means.

15. The instrument and system of claim 14, wherein the surgical microscope means includes intensified video camera means for imaging at low light levels at high magnification while remaining within safe illumination levels for human clinical procedures.

16. The instrument and system of claim 14, wherein the display means comprises a video screen divided to show the image from the surgical microscope means as well as topography information obtained from the three dimensional mapping means and generated by said microprocessor means.

17. The instrument and system of claim 14, further including eye illumination means also along the common optical path with the laser beam, the surgical microscope and the three dimensional mapping means.

18. The instrument and system of claim 14, further including optical zooming mean associated with the surgical microscope means, for forming an image of adjustable magnification range of not less than tenfold increased magnification, of said small region of the eye with optical elements located a considerable and comfortable distance from the patient.

19. The instrument and system of claim 18, wherein the optical path includes a final focusing lens at the exterior of the instrument, with the final focusing lens positioned at least 100 mm from the patient's eye.

20. A system for facilitating precisely controlled surgery using a focused laser beam, comprising,

user interface means for presenting information to a surgeon/user and for enabling control of the surgical procedure by the surgeon/user, including video display means for presenting precise information to the surgeon/user relating to the location in a patient's tissue at which the system is targeted, and the three-dimensional topography and contours of features of the subject tissue and including means for displaying images of cross sections of portions of the patient's tissue, and including means in the control of the surgeon/user for scanning across the tissue to change the information on the video display means as desired by the surgeon/user and for enabling control of the firing of a surgical laser beam by the surgeon/user,

an imaging system connected to the video display means, including three-dimensional mapping means for generating, reading, and interpreting data to obtain information regarding the location in three dimensions of significant features of the tissue to be operated upon, and including microprocessor means for interpreting the data and presenting the data to the video display means in a format useful to the surgeon/user,

a short pulse visible light laser power source for generating a laser beam capable of effecting the desired laser surgery in the patient's tissue, including within transparent tissue of the patient,

optical path means for receiving the laser beam and redirecting the laser beam and focusing it as appropriate toward a desired target in the tissue to be operated upon,

surgical microscope means positioned to intercept and to be coaxial with the optical path means, for taking surgical microscopic images of said target along the optical path means and for feeding video image information to the video display means, and

tracking means in the optical path means and associated with the microprocessor means, for tracking movements of the subject tissue at which the system is targeted without damaging the subject tissue before the next pulse of the laser is fired and shifting the optical path means accordingly before the next pulse of the laser is fired, such that information and images generated by the three dimensional mapping mans and by the surgical microscope means, as well as the aiming and position of the laser beam, follow changes in position of the tissue.

21. The laser surgical system of claim 1, further including first control interlock means for preventing firing of the surgical laser beam except when the tracking means is properly tracking movements of the subject tissue at which the system is targeted, by preventing the laser from firing a next pulse of energy unless the tracking means has tracked the subject tissue.

22. The laser surgical system of claim 1, further including means for superimposing program templates over images created by the imaging system, for automatically effecting a pre-selected pattern of laser surgery.

23. The laser surgical system of claim 1, wherein the imaging system includes scattered light detection means for detecting scattered light from the features of the tissue, with means for filtering out substantially all specularly-reflected light for the scattered light detection means.

24. The laser surgical system of claim 1, wherein the surgical microscope means includes an intensified video camera means for imaging at low light levels at high magnification while remaining within safe illumination levels for human clinical procedures.

25. The laser surgical system of claim 1, wherein the optical path means includes a final focussing lens with means for focussing the laser beam, the three dimensional mapping means and the surgical microscope means an appreciable and comfortable distance from the final focussing lens with respect to the patient, a distance of not less than about 50 mm.

26. The laser surgical system of claim 25, including an objective lens assembly of which the final focussing lens comprises a front element, and wherein the tracking means includes a turning mirror under automatic control of the microprocessor means, with the turning mirror positioned within the objective lens assembly and movable with respect to the final focussing lens.

27. The laser surgery system of claim 1, including tracking and profilometer camera means associated with the three dimensional mapping means and with the tracking means, also intercepting and directed along said optical path means and having an angle of view, for obtaining data from the patient's tissue along said optical path means and for sending data to the microprocessor means of the imaging system, for generation of topographical information to the presented on the video display means.

28. The laser surgery system of claim 27, wherein the tracking means includes a electromagnetically driven turning mirror which affects the angle of view of the tracking and profilometer camera means and also the aim of the surgical microscope means and the laser beam, the electromagnetically driven mirror being under the control of signals generated by the microprocessor means of the imaging system to follow recognized features of the patient's tissues after movement of that tissue.

29. The laser surgery of claim 1, wherein the tracking means includes fast tracking means for tracking movements of the tissue at tracking closed loop response times of one millisecond or less.

30. The laser surgery system of claim 29, wherein the tracking means further includes backup slow tracking means for analyzing tissue position based on the three-dimensional topography of the tissue as determined, and for searching and finding, using the microprocessor means, a feature of the tissue when that feature is not found by the fast tracking means within a predetermined time and for shifting the optical path means to reposition the optical path means on the tissue feature.

31. The laser surgery system of claim 30, wherein the backup slow tracking means includes a video camera having a frame rate, and wherein the slow tracking means operates at tracking closed loop response times equal to the video camera frame rate.

32. A system for use in ophthalmic laser surgery, comprising,

a laser source for producing a pulsed visible light laser beam having a power capable of effecting a desired type of surgery at targeted tissue at a selected surgical site in the ocular tissues,

optical path means for delivering the laser beam, including beam directing means for controlling aim and depth of focus of the laser beam,

three dimensional mapping means for sensing locations, shapes and features on and in a patient's eye in three dimensions, and for generating data and signals representing such locations, shapes and features,

display means receiving signals from the three dimensional mapping means, for presenting to a surgeon user images representative of said locations, shapes and features of the eye including at depths in the eye selectable by the surgeon,

position analysis means associated with and receiving signals from the three dimensional mapping means, for recognizing the occurrence of changes of position of features of targeted tissue of the eye,

target tracking means associated with the position analysis means, for searching for a feature of targeted tissue and finding the feature's new position after such a change of position, and for generating a signal indicative of the new position of the targeted feature tissue, and

tracking positioning means for receiving said signal from the target tracking mean and for executing a change in the aim of the three dimensional mapping means to the new position of a targeted tissue feature to thereby follow the feature and stabilize the images on the display means, and for simultaneously and accordingly adjusting the aim of the laser beam to be directed at a new position of the targeted feature.

33. The system of claim 32, further including pre-programmed surgery execution means for automatically controlling timing of laser firing in conjunction with automatically controlling the beam directing means as to laser aim and depth of focal point in accordance with a preselected surgical path in three dimensions, to fully automatically execute a selected surgical procedure on the eye, and including tracking feedback means associated with the target tracking means and the surgery execution means, for sending signals to the pre-programmed surgery execution means to confirm that a feature's new position has been found, and to discontinue laser firing if such a confirming signal is not received by the surgery execution means within a preselected period of time.

34. The system of claim 32, wherein the display means is a video display monitor, and further including surgical microscope means positioned to intercept and to be coaxial with the optical path means, for taking video microscopic images of target areas of the ocular tissue and for feeding video image information to the video display monitor to cause such video microscopic images to be displayed, assisting the surgeon in the laser surgery.

35. The system of claim 32, further including surgeon control means connected to the beam directing means for enabling a surgeon user to control the aim and depth of focus of the laser beam.

36. A method for conducting laser surgery, comprising,

providing a system for imaging a patient's tissue in three dimensions, displaying images is selected formats on a display screen in front of a surgeon, delivering a visible light laser beam at the patient's tissue and firing the laser in accordance with a surgical path in three dimensions as selected by the surgeon directing the laser and for tracking the patient's tissue so as to stabilize images presented on the display screen and to essentially immobilize the subject target tissue on the display screen in spite of actual movements of the tissue,

placing a patient adjacent to the system,

under control of the surgeon, reviewing the patient's tissue at different locations and along different cross-sections by selection of desired images on the display screen,

under control of the surgeon, selecting a surgical path in three dimensions for surgery on the subject tissue and comprising a series of locations for targeting the focal point of and firing the laser beam to effect the surgery, and entering the precise surgical path as selected by the surgeon into a computer and memory of the system,

under control of the surgeon, initiating the firing of the laser along the programmed surgical path selected by the surgeon, and

automatically interrupting the surgery along the programmed surgical path whenever the tracking device of the system has failed to relocate a moved tissue feature within a pre-selected period of time.

37. The method of claim 36, further including the surgeon's surveying video microscopic images of the subject ocular tissue along with the other images displayed on the screen, as a guide to the surgeon in controlling the laser surgery, using a surgical microscope which views the patient's eye tissue at substantially the same region viewed by the three dimensional imaging system, with the system having means for presenting a video microscopic image of the subject targeted tissue on the display screen.

38. A method for conducting ophthalmic laser surgery using an imaging system which displays for the surgeon precise information as the location and configuration of features of the patient's eye and as to the aim and depth of focal point of a surgical laser beam, comprising,

generating with a laser source a visible light laser beam having a power capable of effecting a desired type of surgery in the eye,

delivering the laser beam along an optical path,

controlling aim and depth of focus of the laser beam with a beam directing means associated with the laser optical path,

sensing locations, shapes and features on and in a patient's eye in three dimensions with a three dimensional mapping means, and generating data and signals representing such locations, shapes and features,

presenting to a surgeon user images representative of said locations, shapes and features of the eye at the target site, on a display mans which receives signals from the three dimensional mapping means including images of cross sections of portions of the eye,

recognizing the occurrence of changes of position of features of the at the targeted site, with a position analysis means associated with and receiving signals from the three dimensional mapping means,

searching for a target site feature and finding the target site feature's new position after such a change of position ,and generating a signal indicative of the new position, with a target tracking means associated with the position analysis means, and

automatically executing a change in the aim of the three dimensional mapping means to the new position of the feature with a tracking positioning means receiving said signal from the target tracking means, to thereby follow the target site feature and stabilize the images on the display means, and simultaneously and accordingly adjusting automatically the aim and depth of the focus of the laser beam to be directed at the new position of a feature targeted.

39. The method of claim 38, further including the step of reviewing by the surgeon different cross-sections of the ocular tissues by manually selecting different formats to be presented on the display means.

40. The method of claim 38, further including monitoring the patient's tissue with a surgical microscope, and sending signals from the surgical microscope to the display means to present video display of greatly magnified images of the eye tissue, with the surgical microscope sharing a common optical path with the laser beam, including a final focussing lens, such that the video microscopic images displayed comprise a microscopic region at the same location and focal depth that the laser beam is directed.

41. The method of claim 40, including illuminating the patient's eye tissue at a low light level within a safe illumination level for human clinical procedures for said monitoring of the patient's tissue on the video display, the surgical microscope including an intensified video camera for imaging at low light levels at high magnification.

42. The method of claim 38, further including performing laser ophthalmic surgery automatically, in accordance with pre-programmed surgical paths in three dimensions, by selecting a software-based surgical path and initiating the program to automatically aim, focus and fire the laser sequentially at the preselected points establishing the surgical path.

43. The method of claim 42, further including automatically interrupting the aiming and firing of the laser along the pre-programmed path whenever the target tracking means fails to relocate a moved feature within a preselected period of time, thereby interrupting the execution of the pre-programmed surgery immediately when the ocular features subjected to the surgery become transposed an unsafe distance from the intended focal point of the laser beam.

44. The method of claim 42, wherein the system includes surgeon-controlled means for writing and editing pre-programmed surgical path templates, and the method including the surgeon's writing a pre-programmed surgical template before initiating the automatic execution of the surgery along the pre-programmed path.