Surgery – Instruments – Light application
Reexamination Certificate
1994-03-11
2001-07-31
Shay, David M. (Department: 3739)
Surgery
Instruments
Light application
C606S004000, C606S011000, C606S013000
Reexamination Certificate
active
06267756
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for the observation and the treatment of the eye using a laser.
State of the Art
By way of illustration, the observation of the rear portion of the eye poses the problem that the illumination and the observation must be conducted through the pupil of the eye and the often optically turbid front eye mediae, where reflexes occur and which cause aberration errors.
For this reason, it has often been suggested not to illuminate large areas of the background of the eye, but to scan as small as possible a spot with a focussed light and to detect the reflected light in ratio to the scanning sequence. In this connection, reference is made, by way of illustration, to “The Foundations of Ophthalmology”, vol. VII, p. 307, 308, 1962, the U.S. Pat. No. 4,213,678 and the Japanese Patent Publications 61-5730 and 50-138822.
The apparatuses known from the above-cited references differ, e.g. in pupil separation: a “GULLSTRAND pupil” is suggested in the Japanese Patent Publication 61-5730 for the illumination and observation light, in U.S. Pat. No. 4,213,678 it is an inverted “GULLSTRAND pupil” and in the Japanese Patent Publication 50 138822 it is adjacent pupils.
Furthermore, an apparatus for the observation of the rear portion of the eye is described in EP-A-O 145 563. In the apparatus the illumination and the observation light beam are directed via a scanning device. Such a “double scanning system” has the advantage that the reflected light beam can be demonstrated with a stationary detector having a relatively small surface.
The good image quality, that these known apparatuses deliver, predestine these apparatuses also for use in the treatment of the eye using a laser, as has already been suggested in U.S. Pat. No. 4,213,678.
Nonetheless these apparatuses could not gain ground as treatment devices for the following reasons:
The operator does not only have to refind the location to be treated, but also adjust the laser when the eye moves. These operations, which are also required with other laser treatment apparatuses, are, however, made more difficult with the prior described apparatuses due to the fact that the visual representation displayed on the monitor is monochrome and, thus, unaccustomed for the ophthalmologist, as the eye is illuminated by the light of the laser. Therewith the identification of the structures is made more difficult.
On the other hand, an apparatus of another type has been suggested in DE-OS 34 25 975, which provides a projection device, which, in particular, projects an angiograph of the eye to be treated in the path of the observation beam.
However, with the apparatus known from DE-OS 34 25 975 the operator must also not only make the projected visual representation concur with the image actually seen of the eye to be treated, but also constantly “adjusts” the laser, when the eye of the subject moves a little. Facilitated is only the identification of the location to be treated.
It is quite understandable that said two operations—adjusting the path of the obervation beam, by way of illustration of a slit lamp in order to make the angiograph concur with the visual representation of the fundus, adjusting the laser to the coagulation location—put a great strain on the operator. Such a strain can, under circumstances, lead to operation errors and thus to unfavorable treatment results.
Furthermore, an apparatus employing an indirect ophthalmoscope has been suggested, which is provided with a control unit which adjusts the laser beam to the movements of the eye (ARVO-Abstracts, vol. 38, Summary No. 92). The known apparatus is provided with an image processing unit, which analyzes the visual representation delivered during the treatment by an image indicating device. The adjustment ensues in the known apparatus in such a manner that the operator can select a well-defined area, by way of illustration a branching blood vessel and the control unit adjusts the laser beam in such a manner that the distance ratio of the location to be treated to the well-defined area remains constant during the treatment. The reason for this method of approach is that the present image processing sing units, which are realizable at cost prices affordable for ophthalmologist practices are not able, by way of illustration, to analyze the entire background of the eye in “real-time”, as would be necessary in order to realize the adjustment while taking the entire indicated area into consideration.
The known apparatus, however, does not take into consideration that “morphologically” similar areas can occur in a human eye within the scope of the analysis of a typical image processing unit, by way of illustration branching blood vessels. In the event of rapid eye movement, it is therefore possible that the control unit indicates another “morphologically similar” branching blood vessel as the area initially selected and erroneously identifies this area as the area to which the distance ratio is to be held constant. In such a case, the control unit will align the laser to a different area than the area to be treated. It is not necessary to go into further detail that unacceptable damage to the eye can occur with the known apparatus.
DESCRIPTION OF THE PRESENT INVENTION
The object of the present invention is to improve an apparatus for observation and treatment of the eye using a laser in such a manner that facilitates the operation, on the one hand, and, on the other, excludes sources of errors due to erroneous alignment of the laser.
According to the present invention it has been recognized that one source of error in laser treatment and, in particular in the case of laser coagulation, is that the operator is, for a number of reasons, under pressure of time during the treatment when he mistakes an area, which is similar in structure, for the location to be treated, which he is supposed to find again by means of specific structures. According to the present invention, it has, therefore, been provided that a visual representation, on which the location or locations to be treated are marked, is superimposed upon the visual representation recorded by the detector device. By means of these markings, errors, by way of illustration caused by erroneous identification of structures, can be avoided.
As additional aid for the operator, the control unit prepositions the laser beam in such a manner that it is focussed on the marked location.
A combination of these features makes it possible for the treating ophthalmologist to draw up an operation plan at his leisure prior to the actual commencement of the treatment by seeking the locations to be treated, by way of illustration the locations to be coagulated, on a visual representation of the eye to be treated and marking it. During that part of the treatment when the patient is sitting in the operating chair and, during which, experience has shown, it is necessary to act quickly, the control unit provided in accordance with the present invention pre-positions the laser beam for the ophthalmologist so that the ophthalmologist only has to satisfy himself that the pre-positioning is good, perhaps make necessary corrections and subsequently release the laser beam.
On the other hand, by means of the invented combination of features the operator, i.e. the treating ophthalmologist, can check the quality of the positioning of the laser beam at any time by means of the visual representaton additionally superimposed upon the monitor, which, by way of illustration, shows the entire background of the eye. As the operator can check the concurrence of the superimposed visual representation with the actual image of the eye over a large area, “laser misses”, which occur when two similar-looking areas have mistakenly been made to concur, cannot happen. Notwithstanding, the invented apparatus requires only a little computation, as by way of illustration not the entire, very strongly structured background of the eye has to be checked, but only the laser beam has to be adjusted to a marking.
Naturally, it is al
Bisle Werner
Eisenträger Wolfgang
Feuerstein Manfred
Klingbeil Ulrich
Langosch Herbert
Antonelli Terry Stout & Kraus LLP
G. Rodenstock Instrumente GmbH
Shay David M.
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