Method and apparatus for monitoring laser surgery

Abstract

A method and system for laser surgery produces controlled laser pulses and simultaneously verifies that a correct sequence of pulses are being delivered to the patient. A photo detector receives a predetermined portion of the energy of the treatment pulses as they exit the system. A separate monitoring computer compares an output signal from the photo detector with reference information for the treatment sequence. The system is exemplified in an implementation in an ophthalmic laser surgery system.

1 . In a system for producing a predetermined treatment pattern of laser pulses for selectively ablating the cornea of a patient, said system including a laser for producing laser light pulses, an electro-optical system for controlling pulses of laser light from the laser so that selected portions of the cornea of the patient are ablated in accordance with the predetermined treatment pattern and a treatment computer which runs a treatment algorithm based on inputted treatment parameters to produce the predetermined treatment pattern, a monitoring system for monitoring the delivered laser pulses comprising: 
 a detector for producing signals during treatment indicative of sampled laser pulses being delivered to the patient over a selected time interval; and    a fail-safe computer 
 for separately running the treatment algorithm to provide reference values for sampled pulses responsive to separately inputted treatment parameters,  
 for comparing signals from the detector with the reference values; and  
 for providing a signal indicative of the performance of the system in response to the comparison.  
   
     
     
         2 . The system of  claim 1 , further comprising means for producing a display of the spatial energy distribution of the laser pulses being delivered to the patient.  
     
     
         3 . The system of  claim 1  further comprising memory for storing energy distribution information derived from the signals produced by the detector.  
     
     
         4 . The system of  claim 1 , further comprising means for controlling the production of the treatment pattern of laser pulses in response to the signal indicative of the performance of the system.  
     
     
         5 . The system of  claim 4 , wherein the controlling of the system in response to the signal indicative of the performance of the system includes shutting down the system upon detection of an improper spatial energy distribution.  
     
     
         6 . The system of  claim 1 , wherein the system is a broad beam system using pulses having a spot diameter of from ½ to 8 mm on the cornea of the patient.  
     
     
         7 . The system of  claim 1 , wherein the electro-optical controlling system scans the laser pulses across an area of the cornea to be ablated.  
     
     
         8 . The system of  claim 7 , wherein the system is a flying spot scanner.  
     
     
         9 . The system of  claim 8 , wherein the system uses laser spots having a diameter between 1 and 2 mm and a pulse rate between 50 and 200 Hz.  
     
     
         10 . The system of  claim 7 , wherein the system is a slit scanning laser system.  
     
     
         11 . The system of  claim 1  wherein the detector is an electronic camera and wherein the laser pulses are focused to produce images of the laser pulse spots.  
     
     
         12 . The system of  claim 1 , wherein the detector is an electro-optic detector for producing electronic monitoring signals in response to 193 nm UV laser light pulses.  
     
     
         13 . A method for monitoring a laser surgery system which produces a sequence of varying types of treatment pulses in accordance with a treatment algorithm run by a treatment computer, comprising the steps of: 
 sampling laser pulses in a sequence of calibration pulses of various types, so as to apply a predetermined portion of light energy of the pulses to a photo detector;    providing output signals of the photo detector to a monitoring computer and associating the output signals of the photo detector with corresponding calibration pulses of various types to obtain a reference value for each type of pulse;    sampling treatment laser pulses so as to apply a predetermined portion of the light energy of each treatment pulse to the photo detector; and    comparing an output signal from the photo detector corresponding to a treatment laser pulse with a reference value for that type of pulse, wherein the reference value is obtained by using a treatment algorithm in the monitoring computer to identify the type of pulse which should be being administered in the treatment sequence and to select the corresponding reference value for that type of pulse.    
     
     
         14 . The method of  claim 13 , wherein the treatment algorithm run in the treatment computer is the same treatment algorithm used by the monitoring computer.  
     
     
         15 . The method of  claim 14 , wherein treatment parameters are separately applied to the treatment computer and monitoring computer for use in the treatment algorithm.  
     
     
         16 . The method of  claim 15 , wherein the surgery is ophthalmic laser surgery and the treatment parameters are refractive and astigmatism corrections appropriate for the patient.  
     
     
         17 . The method of  claim 16 , wherein the treatment parameters are used by the treatment computer to select iris settings and slit dimensions which vary the spatial dimensions of the laser pulses to produce the various types of laser pulses.  
     
     
         18 . A system for providing and monitoring laser pulses produced in accordance with a predetermined treatment sequence and directed at the cornea of a patient to modify the cornea by photo ablation and for verifying that the predetermined treatment sequence of pulses is being delivered to the patient comprising: 
 a laser for producing laser pulses;    an electro-optical system for controlling the pulses in response to signals from    a first, treatment computer which controls the electro-optical system in accordance with a treatment algorithm based on inputted treatment parameters;    a detector for detecting calibration pulses and pulses in the treatment sequence; and    a second, fail-safe computer for monitoring the performance of the system while the treatment sequence is ongoing by comparing the treatment monitoring signals for at least some of the treatment pulses with corresponding reference values derived from the calibration pulses, the reference values being indicative of the expected treatment monitoring signals for treatment pulses produced during the treatment sequence, said reference values being determined from data entered into the fail-safe computing device separately from the data entered into the treatment computing device, said separately entered data being indicative of the patient's treatment sequence, and from at least one detected calibration pulse for the same type of pulse measured during calibration.    
     
     
         19 . The system of  claim 18  further comprising a beam splitter which acts as a turning mirror and reflects laser pulses from its front surface directly to the cornea of the patient.  
     
     
         20 . The system of  claim 19 , wherein laser light received by the detector is transmitted through the beam splitter.  
     
     
         21 . The system of  claim 19 , wherein the beam splitter has a front surface mirror which reflects laser pulses to the cornea of the patient.