Surgery – Instruments – Light application
Reexamination Certificate
2002-02-25
2004-04-27
Gibson, Roy D. (Department: 3739)
Surgery
Instruments
Light application
C606S006000, C128S898000
Reexamination Certificate
active
06726679
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and a device for treating opacities and/or hardenings of an unopened eye. Specifically, the present invention relates to a laser system and a method for cleaning, in particular, the ageing human eye from gray hazes in the cornea, the lens or the vitreous body to restore transparency in the eye.
In ophthalmology, it is known that, in particular in the ageing eye, opacities develop in the lens (cataract) or in the vitreous body or the cornea. At the advanced stage, the treatment is presently limited to replacing the lens with a plastic lens during a cataract surgery, replacing the vitreous body with silicone oil by vitrectomy, or also to transplanting the cornea. It is known to carry out the surgery of the cataract and the vitrectomy of the vitreous body using a laser. During a surgery, the laser beam is in both cases led directly to the tissue to be treated. A proven efficient laser is, in particular, the Er:YAG laser having the emission wavelength of 2.94 &mgr;m whose radiation is strongly absorbed by water. For conveying the laser radiation, cannulas with optical waveguides are led up to the location of treatment. Although cannulas having diameters of approximately 1 mm are manufacturable now, the necessity of the surgical intervention remains. A device for carrying out a laser phacoemulsification is described, for example, in German Patent 19718139.
Also known are surgical techniques in the case of which the eye is not opened but the laser light is guided into the eye via the normal path of the visual process. These techniques include the possibility of attaining an optical disruption inside of the cornea by focusing fs laser pulses (300 fs, 1 &mgr;J, 780 nm), resulting in the formation of blisters. By folding open a lamella, it is possible to prepare an intrastromal lenticle whose removal brings about a refractive correction. It is known, moreover, that the gray after-cataract membrane can be disruptively removed with the aid of ns pulses of a Q-switched Nd:YAG laser.
In known methods heretofore, apart from medicamentous methods, it was not possible to treat the clouded regions already at the initial stage. Thus, the known laser techniques are not suitable for removing the clouded regions in the eye without opening the eye. Therefore, it is an object of the present invention to provide a method and a device which make it possible to dissolve clouded regions in the eye.
A further phenomenon which occurs in old age is presbyopia. One reason for this lies in the hardening of the lens, which can occur, for example, due to deposit of substances. Apart from the utilization of spectacles, photorefractive keratectomy (PRK) has often been used recently for correcting the visual defect. Removal of the hardening itself has not been possible in known methods heretofore. Therefore, it is a further object of the present invention to provide a device with which the lens' ability to contract is increased again.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a method and a device which make it possible to dissolve opacities and/or hardenings of an eye.
This objective is achieved, in particular, by a method for dissolving opacities and/or hardenings of an unopened eye in connection with which the opacities and/or hardenings are dissolved via at least one ultrashort pulse of a laser without opening the eye. By using an ultrashort pulse which is sent through the transparent eye structure, no thermal or athermal damage is produced on the retina or other uninvolved regions. In the working plane (for example, the lens, the vitreous body or in the cornea), there exists an energy density of such a kind that indeed nothing happens in the fully transparent medium of the eye but that disruptions are induced at heterogeneous spots of clouding by local absorption, the disruptions dissolving these impurities. These disruptions result in the evaporation of these impurities.
The gas blisters (cavities) possibly forming in the process are filled up in a few hours and disappear in this manner. The dissolved impurities are reduced by resorption and/or dispersion, or disappear completely.
Pulses which lie in the ps range are preferably used as ultrashort pulses; particular preference being given to pulses which lie in the fs range. It is preferred to use pulses of from 10 ps to 10 fs, particularly preferably of 300 fs.
The special advantage of the method according to the present invention lies in that the opacities and/or hardenings of the eye can be removed or reduced without having to open the eye. In this manner, the risks involved in surgery are avoided. Using the method according to the present invention, moreover, a treatment which is more gentle and carried out in small steps can be accomplished by appropriate selection of the energy of the ultrashort pulse.
It is preferred for the ultrashort pulses to be further amplified, particularly preferably via the Chirped Pulse Amplification Method (CPA method).
In a preferred method according to the present invention, the opacities and/or hardenings are dissolved with the assistance of a pulse train having a duration of less than 5 s, preferably less than 3 s, particularly preferably less than 0.1 s of the ultrashort pulses. It is very particularly preferred to provide pulse lengths in the range of from 10 ps to 10 fs, and especially preferably of approximately 300 fs. The energy input in the region to be treated can be predetermined via the selection of a pulse train by determining the duration. By selecting extremely short pulse trains, it is possible, moreover, to prevent efficiency losses which could occur, for example, because of a movement of the eye during the treatment. The pulses particularly preferably have a duration of less than 10 ps. It is also conceivable to use the pulse train in continuous operation until the desired effect has been attained. Very particularly preferably, it is also possible to use single pulses and very short pulse trains to achieve a particularly gentle treatment by iteratively monitoring the success of treatment.
In a further preferred method of the present invention, pulse trains with a repetition frequency, in particular, with a repetition frequency in the kHz range are emitted. In this connection, the pulse trains themselves are superposed with a repetition frequency once again. In this manner, the energy input into the region to be treated can be varied over time once more in spite of the selection of a longer pulse train or even of a continuous operation. Because of this, an even more gentle treatment is possible, avoiding any thermal or athermal damage to the eye in regions which are not intended to be treated.
In a further preferred method of the present invention, one chooses a laser radiation of a wavelength distribution which has a higher absorption and/or a lower reflection for the opacities and/or hardenings than for the remaining parts of the eye. In this manner, it is possible to adjust the energy density in such a manner that the density required for triggering an optical breakdown is only reached at locations of local absorption. This selective adjustment is attained through the increased absorption of the opacities and/or hardenings at the selected wavelengths. It is particularly preferred to chose a laser for whose wavelength the eye is highly transmissive. The wavelength is preferably 350 to 1300 nm. It is particularly preferred to chose a laser to whose radiation the sensitive regions such as the retina or the macula are somewhat less sensitive. This can be accomplished via a lower absorptivity of these regions in the eye for the selected radiation. This can also be achieved by a higher reflectivity of the regions of the eye which are not to be treated. Thus, the radiation cannot cause any damage in the regions of the eye which are not to be treated just because of the absorptive and reflective behavior, independently of the energy density which can be generated by focusing.
In a further pr
Dick Manfred
Schroeder Eckhard
Asclepion Meditec AG
Davidson Davidson & Kappel LLC
Gibson Roy D.
Johnson, III Henry M.
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