Surgery – Instruments – Light application
Reexamination Certificate
1999-03-05
2001-11-06
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
Light application
C606S005000, C606S011000, C606S012000, C606S017000, C128S898000, C351S200000, C351S205000, C351S219000
Reexamination Certificate
active
06312422
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a process and arrangement for monitoring and controlling the treatment parameters in an ophthalmic treatment device, especially for adjusting and monitoring the application of the actual amount of radiation (treatment parameter) to be applied to the specific patient in photodynamic therapy (PDT) of diseased tissue in the fundus of the eye, especially for the treatment of age-related macular degeneration which usually leads to a (progressive) destruction of the central retinal portions with irreversible loss of visual function. In the proliferative form of macular degeneration, a neovascularization which originates in the choroid and destructively grows under and into the retina of the eye is responsible for the course of the disease. Harmful scarring occurs in the end stage.
b) Description of the Related Art
It is known to isolate thromboses and neovascularization in the eye through photodynamic therapy in that a selective and localized treatment of the affected locations and tissue parts of the eye is carried out through photodynamic effects. For targeted implementation of such treatment of diseased tissue, the patient is injected with photosensitizers which selectively concentrate in diseased tissue parts of the eye after a certain period of time and enable effective radiation treatment with laser light of suitable wavelength.
Lasers are preferably used for photosensitization after injection with sensitizers, these lasers emitting a wavelength of adjustable output suitable for exciting the photosensitization, wherein the adjusted output value depends, among other things, on the injected dye and on any opacity which may be present in the eye to be treated.
The light emitted by the laser is coupled into an applicator via suitable optical elements, e.g., light guides, wherein the light is directed onto the portion of the retina of the eye to be treated by means of the applicator. The setting parameters, such as the diameter of the treatment area and the radiation output, are determined and adjusted by the treating physician.
A target beam which assists the physician in orienting the applicator in such a way that a treatment beam can expose the surface to be treated in the eye is generated by a second, substantially weaker laser which emits light of a different wavelength. This target beam is also coupled into the applicator through the optical elements.
Treatments should take into account patient-related parameters such as the size of the area to be treated in the eye, consideration of the influence of any opacity that may be present in the eye of the patient, and maintaining a defined maximum radiation intensity and dye-related parameters (energy flux density). However, in currently used laser systems, only the parameters of output, energy and duration of irradiation can be adjusted in the device. Thus, it is disadvantageous that in order to adapt the actual parameters to be used the physician or user must convert the individual values by means of tables or other means and must guarantee that these values are maintained. This method is a source of human error on the part of the physician or user and can have direct consequences on the success of the treatment.
OBJECT AND SUMMARY OF THE INVENTION
Therefore, it is the primary object of the invention to eliminate these disadvantages of the prior art and to provide a process and an arrangement for monitoring and controlling the treatment parameters in an ophthalmic treatment device by which a photodynamic therapy of diseased tissues in the eye which is extensively free from human error can be achieved and by which a reliable handling and adjustment of these devices is made possible.
According to the invention, this object is met by an ophthalmic process for mounting and controlling the adjustment of treatment parameters in an ophthalmic treatment device which comprises a radiation source generating at least a treatment beam and, optionally, a target beam and an applicator which is connected with the radiation source via at least one optical element, wherein the applicator can be attached to a slit lamp comprising the steps of adjusting, by the operator at the radiation source, the radiation parameters such as intensity, magnification of the contact lens placed on the eye, radiation dose per unit area, and spot size on the retina; calculating first parameters to be adjusted at the applicator on the basis of patient-related influencing variables such as contact lens magnification and the size of the spot to be realized on the retina, so that a determined spot size and intensity of the treatment beam to be applied can be realized at the treatment site on the retina; and comparing the parameters adjusted at the applicator with the first parameters by a computer and making the adjusted parameters coincide with the first parameters representing reference values and the parameters serving as reference values being realized and maintained constant for the duration of the radiation. According to an arrangement, it is made possible to carry out the process in a simple manner in an ophthalmic device, wherein the device comprises a radiation source generating a target beam and a treatment beam and has a computer or a control unit and an applicator which directs the radiation into the eye to be treated and enables observation by the operator. This applicator can be attached to a slit lamp. A laser unit with a target laser and a treatment laser, for example, can be provided as radiation source. The radiation source and the applicator are connected with one another by at least one optical element, for example, a light guide, which transmits the target beam and treatment beam. An information connection is also provided so that radiation parameters and/or other information representing controlling variables can be transmitted between the applicator and the laser unit. This information connection can be constructed in the form of an electrical connection, e.g., in the form of an electrical cable, which can be coupled, e.g., to a part of the applicator at which there is also provided the input of the optical element which is constructed, for example, as a light guide.
During the process, the patient-related and dye-related irradiation parameters such as intensity, magnification of the contact lens used, radiation dose per unit area (energy flux density) and the spot size on the retina are adjusted by the user or operator at the radiation source. Taking into account the influencing variables depending on the patient, such as contact lens magnification and the spot size to be realized on the retina (reference spot size), an appropriate adjustment is carried out by means of a controlling and regulating unit by adjustment means at the applicator so as to achieve a determined, desired intensity and spot size of the treatment beam on the irradiation site in the fundus of the eye. Exactly defined conditions are achieved and maintained during irradiation in that the irradiation parameters adjusted at the applicator are compared with the reference parameters by means of a computer and in that these values are continuously made to correspond to one another and are maintained constant during irradiation.
In this respect, it is advantageous when the intensity of the laser radiation at the irradiation site is compared with the radiation values to be applied and when, in the event of difference between these values, the intensity is maintained constant during irradiation automatically or manually by changing the spot size by means of an optical system provided in the applicator and/or by changing the output of the radiation source. The optical system comprises a beam expansion system and an objective. In order to achieve a high degree of safety for the patient, changes in the adjustment of the spot size are detected automatically by the radiation source by means of the optical system of the applicator and are corrected or the irradiation is interrupted by turning off the laser unt
Carl Zeiss Jena GmbH
Dvorak Linda C. M.
Farah Ahmed
Smith LLP Reed
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