Surgery – Truss – Pad
Patent
1985-06-27
1987-10-27
Cohen, Lee S.
Surgery
Truss
Pad
128395, 372 25, 372 31, A61B 1736
Patent
active
047022450
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a pulsed laser for medical applications, and in particular for ophthalmological treatment purposes.
Neodymium-YAG lasers with mode locking or Q-switching can be used as pulsed lasers. It is also possible to use other pulsed lasers, such as argon lasers.
BACKGROUND ART
Pulsed lasers are used for operations on the human eye. In the case of the known lasers, there is no control of the laser pulse energy prior to the release of the operating pulse. It is readily apparent that if the laser pulse energy is too high, the eye to be treated can be seriously damaged.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a pulsed laser for medical applications and in particular for ophthalmological treatment purposes, in which the energy of the laser pulses can be controlled.
According to the invention this object is solved by regulating the energy of the laser beam pulse, having a clearly defined polarization plane, by rotating a polarization splitter cube and by having a control system release a test pulse after each rotation of the polarization splitter cube. A light-sensitive element measures the energy of the test pulse. The treatment beam path is shut off by a shutter during the test pulse.
The invention makes use of a laser, whose laser beam pulse has a clearly defined polarization plane and in which the energy of a single pulse can be controlled by rotating a polarization splitter cube. As has been recognized by the invention, in the case of such lasers the following causes for incorrect energy release exist:
1. As a result of mechanical errors and faults, the polarization splitter cube is not in its correct desired position, so that it does not permit the passage of the desired laser energy fraction.
2. The energy released by the laser during a pulse does not correspond to the desired energy.
By means of the invention it is now possible that the energy of the two successive laser pulses for lasers used in ophthalmic treatment never fluctuates by more than .+-.20%. Such divergences of the actual energy from the desired energy are acceptable in medical applications and particularly in operations on the human eye.
Thus, no matter which of the two above causes for an incorrect energy release exists, a treatment pulse energy differing in an excessive manner from the desired energy can be detected in that following each rotation of the polarization splitter cube, and prior to the following treatment pulse, a test pulse is released. In order that the test pulse cannot injure a patient or the operator, the test pulse is released internally, i.e. within the laser equipment, because during the release of the test pulse, a shutter shuts off the outwardly directed beam path.
In advantageous further developments of the invention the output signal of the light-sensitive element is used for regulating the energy of the laser pulses and the automatic setting of the rotation angle of the polarization splitter cube. The output signal may also regulate the voltage of the laser flash lamp. The control system may be used to rotate the polarization splitter cube into a position in which it permits the passage of the minimum laser energy when the laser is switched on. The polarization splitter cube may be rotated by an operator by means of a knob with the test pulse being automatically released by the control system when the knob is released. A beam splitter may be arranged in a fixed manner in the laser beam path so as to deflect part of the beam on to the light-sensitive element.
The invention can be used with particular advantage in the case of neodymium-YAG lasers, which are often used for operations on the human eye. As a function of the type of control (passive mode locking or active/passive Q-switching), the energy of such lasers can fluctuate in the aforementioned range. Through the release of a "test shot" or optionally several test pulses prior to the following treatment pulse, it is possible to reliably narrow down the range within which the energy
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Schroder Eckhard
Thyzel Reinhardt
Cohen Lee S.
Meditec-Reinhardt Thyzel GmbH
Shay David
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