Surgery – Instruments – Light application
Reexamination Certificate
1998-08-07
2001-07-10
Peffley, Michael (Department: 3739)
Surgery
Instruments
Light application
C606S010000, C351S213000
Reexamination Certificate
active
06258081
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to an arrangement for laser coagulation at the ocular fundus with at least one illumination light source for an illumination beam path, with a laser arrangement for generating a sighting beam path and a treatment or therapy beam path, wherein the sighting radiation and therapy radiation have different wavelengths, with observation optics for visual observation of the ocular fundus, for selecting the coagulation site and/or for monitoring the results of coagulation, and with a protective mechanism which prevents the laser radiation from penetrating into the eye of the person administering treatment. An individual laser with a plurality of different laser light wavelengths and the combination of a plurality of lasers with different wavelengths and corresponding driving circuits are also possible as a laser arrangement for radiating the sighting radiation and therapy radiation.
b) Description of the Related Art
In laser coagulation on the human eye, the desired therapeutic effect is achieved by thermal alteration of tissue in selected areas of the ocular fundus. For this purpose, energy in the form of laser light pulses is introduced into the tissue. With pulse lengths of 20 to 1000 milliseconds and outputs of around 200 mW, the radiated energy is absorbed, so that the surrounding tissue is heated locally. The success of the coagulation can be identified by a whitish color (necrosis) at the coagulation site and can be observed and monitored by the treating person through visual inspection of the ocular fundus, e.g., by means of a slit lamp. The end of the treatment is determined by observation based on subjective appraisal.
Since the observation light as well as the sighting radiation and therapy radiation penetrate into the patient's eye and are reflected therein during a treatment of this kind, the eye of the treating person is also always at risk and it is accordingly necessary to protect the eye of the treating person from reflected therapy radiation.
According to known prior art, in order to prevent injuries resulting from the reflected therapy radiation, separate component groups or subassemblies are used for the reflection of the therapy radiation into the observation beam path and the optical coupling out of the therapy radiation from the radiation reflected by the ocular fundus before this radiation reaches the eye of the treating physician. In particular, the use of eye protection filters which are swiveled into and out of the radiation coming from the ocular fundus by means of mechanical devices is known.
Since known devices comprise a plurality of component groups and/or must be composed of a number of structural component parts, they have the disadvantage that assembly of such arrangements is complicated and requires extensive space, which undermines the effort toward more economical and also miniaturized medical instruments. In addition, an increasing number of parts in the protective devices require swiveling mechanisms which are more complicated and therefore more susceptible to malfunction. In the event of failure of the swiveling mechanisms, the eye protection filter cannot be swiveled into the beam path and the dangerous therapy radiation can reach the eye of the treating physician.
OBJECT AND SUMMARY OF THE INVENTION
Consequently, it is the primary object of the invention to further develop an arrangement for laser coagulation of the type described above so as to further increase the safety of the treating person.
The object of the invention is met in that an optical element which is arranged in the sighting and therapy beam path is provided as a protective device, wherein this optical element has a plurality of optically active areas whose optical characteristics differ from one another. In this way, an uncomplicated construction of the device which is characterized by an extremely high degree of safety for the treating person is achieved.
It can be provided in an advantageous manner that the optical element has an optically active central area and at least one optically active edge area, wherein the central area is opaque to the sighting radiation and therapy radiation, but reflects this radiation, while the at least one edge area is opaque to the therapy radiation but transparent to the sighting radiation, and wherein the optical element is positioned in such a way that the sighting radiation and therapy radiation coming from the laser impinges on the central area and is deflected by the latter onto the ocular fundus, and the at least one edge area is arranged before the observation optics in the beam path of the sighting radiation and therapy radiation reflected by the patient's eye.
Due to this configuration of the optical element and its arrangement in the beam path, it is achieved, first, that the radiation coming from the laser arrangement, i.e., the sighting radiation as well as the therapy radiation, is reflected by the optical element onto the ocular fundus and, second, that the therapy radiation cannot reach the eye of the treating physician either via the edge area or via the central area because the central area and the edge area of the optical element are both constructed so as to be opaque to the therapy radiation. This eliminates danger in every case.
The edge area is transparent only to the sighting radiation which is reflected by the eye and which, after passing through the edge area, strikes the observation optics and is perceived by the treating physician in a harmless manner and can be utilized to target the coagulation site selected for treatment.
In a further preferred arrangement of the optical element, the central area and the at least one edge area are constructed so as to be transparent to the illumination radiation, and the optical element is arranged in such a way that the illumination radiation reflected by the ocular fundus passes through the optical element to the observation optics. Accordingly, the illumination radiation reflected by the ocular fundus can be used for observing and diagnosing the retina. Depending on the results of the diagnosis, the laser arrangement is switched on for the purpose of initially coupling in the sighting radiation and then, in order to perform the treatment, coupling in the therapy radiation.
The illumination radiation can be mixed in or faded in, for example, by a reflecting structural component part arranged in the beam path between the optical element and the observation optics. In order to achieve this coupling in, the central area is advantageously constructed so as to be dichroitic in that it is transparent to the illumination radiation in the direction of the ocular fundus, but reflects, and is opaque to, the sighting radiation and therapy radiation in the opposite direction, while the at least one edge area is transparent to the illumination light reflected in the patient's eye as well as to the sighting radiation in the direction of the observation optics.
This arrangement is also useful for an uncomplicated and accordingly less cumbersome construction of the arrangement according to the invention for laser coagulation while having an extremely small overall size.
A very preferable construction of the invention in which a stereo microscope is provided as observation optics is characterized in that the dichroitic central area of the optical element is oriented approximately centric to the axis of symmetry of the observation radiation, sighting radiation and therapy radiation reflected by the ocular fundus, and the optical element has two edge areas, each of which is arranged, respectively, in one of the two observation beam paths of the stereo microscope. Accordingly, by means of the arrangement according to the invention, the advantages of stereoscopic viewing can be utilized to their full extent in diagnosing the ocular fundus without endangering the eyes of the treating physician.
Further, it is possible to arrange the optical element such that its position and orientation with respect to t
Festag Karsten
Wengler Peter
Asclepion-Meditec AG
Peffley Michael
Reed Smith LLP
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