DE4001434A1 - DEVICE FOR SURGICAL TREATMENT OF AMETROPY - Google Patents

Abstract

A laser 1 device, for use in ophthalmology, and optionally comprising a UV pulsed laser, has a beam distributor 3 therefor located across the path of the laser beam 2, the distributor 3 being an optical system having, on a common optical axis, e.g. two taper lenses 5, 6 and a telescopic objective 7, and being capable of transforming a parallel cylindrical beam from the laser source 1 into a variable-diameter D2 annular beam 20 with a maximum diameter comparable with the diameter of a human cornea 4. <IMAGE>

Description

The present invention relates to the In the field of medicine, in the field of ophthalmology, especially on surgical treatment facilities ametropia, namely myopia and hypermetropia.

A device for surgical is known Treatment of ametropia using an impulse laser emitter of the ultraviolet range and a former the required distribution of the radiation energy density across the cross section of the radiation beam provides that in the way of the radiation beam mentioned the laser emitter is mounted (see Report of the "Center Scientifique IBM", Paris, France, Document N F 104, 1986, K. Hanna et al., "Excimer Laser Refractive Keratoplasty "). This facility is the shaper of the distribution of the energy density of radiation as a turntable with a slot one in predicted shape.

As a result of the intervention of several radiation pulses of the laser emitter at a certain Ratio of consecutive frequency Impulse and the speed of the slotted disc occur Modification sufficient to correct ametropia the surface shape of the cornea.

However, only part of the corneal surface when using this known device irradiated at once, with the shape of the slit and its angular position at the respective moment related, thereby preserving smooth surfaces of the desired profile difficult is because with every pulse of laser radiation from the cornea a vertical layer Flanks is removed, whose shape with the  Shape of the slot matches. Because of that the surface shape of the cornea obtained approximated by a step surface be so that to produce a stepless Surface a plurality of corneal layers must be removed with a shallow depth. Thereby the operation time is extended and the execution the operation itself difficult because of a precise fixation of the eye in relation to the laser beam accomplished for a long period of time must become. The energy of the Laser radiation is not used effectively, which is another Extends the operating time. The facility is involved in its manufacture, because they have a precise manufacturing accuracy when making the slot and its Rotation mechanism, a precision measurement of its angular position and a precise match of the output of the respective radiation pulse with this requirement.

It also has a surgical facility Treatment of ametropia, especially Myopia known in the article "Am. Journ. Of Ophthalmology; V. 103, No. 3, Part II, M.B. McDonald et al. "Defractive Surgery with the Excimer Laser", p. 469, 1987 ". With this device becomes the former of the radiation energy density distribution in the form of one built in by way of the radiation beam Aperture executed, the diameter of impulse to impulse according to a computer program so discreet is changed so that one for the correction myopia desired modification of the shape of the corneal surface is achieved.

As with the facility described above only a part of the surface of the cornea also in the  Use this facility at once irradiated resulting from that at the time existing diameter of the aperture results in what difficult to achieve a smooth corneal surface, since several corneal layers one shallow depth must be removed. That's why becomes the time of the operation longer and complicating the operation itself, since it is a precise fixation of the Eye in relation to the laser beam on a longer one Takes time. In addition, the Energy of the laser radiation is poorly used, which means the execution time of the operation in turn is extended.

Finally, a facility for surgical treatment of ametropia that a Pulse laser emitters in the ultraviolet range and one assembled by way of its radiation beam Shaper of the distribution of the radiation energy density across the bundle cross-section, provides (PCT / SU 88/00 280).

With this facility, the former provides the Distribution of the radiation energy density an optical Chamber, the first and second opening, which are in Paths of the radiation beam are located in one for the laser radiation transparent material are made while the inner surfaces of the relevant openings rotation surfaces second Represent order like paraboloid, hyperboloid or sphere, the optical chamber with a die Laser radiation partially filled substance is. Through this known device can a smooth corneal surface of a desired Profiles are made.

However, also in this facility  a less effective use of energy of laser radiation are accepted because part of this radiation from within the optical Chamber is absorbed substance which causes an increase in the operating time.

In addition, the manufacture of the Form of rotation surfaces of second order Technological openings in the chamber difficult task. These openings must be with a precise accuracy can be made as each Deviation from the prescribed shape for reduction the manufacturing accuracy of the desired Shape of the cornea in the patient's eye. Quite a bit complicated process also represents the setting the device before the operation.

The present invention is based on the object a facility for surgical treatment ametropia with such a structure of the former the distribution of the radiation energy density over the Develop cross-section of the laser beam, through which the greatest possible effectiveness in Achieved use of the energy of laser radiation will and the facility itself in manufacturing is simple, so increased accuracy is achieved in their manufacture and thus also the duration of the operation increased accuracy in the manufacture of a desired shape of the corneal surface of the eye is shortened becomes.

The essence of the invention is that in the facility for surgical treatment of ametropia, which is a pulse laser emitter of the ultraviolet range and one in the way of his Radiation beam mounted formers of the distribution the radiation energy density over the cross section  of the radiation beam provides, according to the invention this shaper of the distribution of radiation energy density across the cross section of the radiation beam represents an optical system that has at least two cone lenses arranged on an optical axis and includes a telescopic lens, and that a cylindrical one Parallel beam of laser radiation to a ring beam of a variable Can convert diameter, its maximum value with the size of the cornea diameter of the eye is compare.

In the device according to the invention for surgical Treatment of ametropia can be the shaper of Distribution of the radiation energy density from two cone lenses consisting of running with their tips face each other and have the same angle of refraction own, while the telescopic lens behind the second cone lens in the beam path can be arranged.

The mentioned form of the distribution of the radiation energy density can also consist of three cone lenses are carried out, of which the second and third in the way of radiation with their bases Laser emitters face and have the same refractive angle have while the telescopic Objective between the first and second cone lens can be built in by way of radiation.

Finally, the shaper of the distribution of the radiation energy density can be made up of three cone lenses, the base surfaces of which face the laser emitter, while the telescopic lens is installed between the first and second cone lenses by means of laser radiation, the third cone lens by reversing in the way of laser radiation Conicity and with a refractive angle equal to 90 ° - α is to be carried out, where α means the refractive angle of the second cone lens by means of laser radiation.

It is expedient to use laser radiation second cone lens in all versions to be arranged adjustable along the optical axis.

Those carried out according to the present invention Surgical treatment facility Ametropia enables accuracy at Production of a desired surface shape Cornea due to a significant reduction in the duration of treatment to increase. The shortening the duration of treatment results from the fact that to every moment on the treatment surface of the cornea the whole emerging from the laser emitter Radiation attacks while the energy losses in the shaper of the distribution of the radiation energy density in the device according to the invention to a minimum are returned. In addition, the invention Setup easily to the desired one Correction size of the ametropia set be, this setting by adjusting a the cone lenses in the distribution former with the help of a stepper motor. The production the cone lens represents a technologically simpler Task compared to making the openings the aforementioned optical chamber, which are limited by surfaces of rotation of the second order, whereby the device according to the invention in the manufacture is easier and with a fairly high one Accuracy can be manufactured.

The invention will now be described in the following concrete embodiments and the Drawings explained in more detail; it shows:

Fig. 1 - a variant of the inventive device for the surgical treatment of ametropia with two cone lenses in a schematic representation;

Fig. 2 - an embodiment variant of the device with three cone lenses;

Fig. 3 - an embodiment variant of the device with a third conical lens of inverted conicity;

FIG. 4 - eye in the treatment of myopia with the device shown in FIG. 1 in a schematic representation;

Fig. 5 is the same in the case of hyperopia;

Fig. 6 eye in the treatment of myopia with that shown in Fig 2 and 3 respectively represented device in a schematic representation.

Fig. 7 the same for the hypermetropia case.

The device according to the invention for the surgical treatment of ametropia, namely myopia and hypermetropia, which is shown in FIG. 1, contains a pulsed laser emitter 1 of the ultraviolet range and a former 3 mounted in its radiation beam 2 for distributing the radiation energy density of the laser beam 1 over the cross section of the radiation beam 2 , which determines the diameter of the operating zone on the cornea 4 of the patient's eye.

The former 3 of the radiation energy density distribution represents an optical system which includes conical lenses 5 and 6 which are arranged one behind the other on an optical axis and which face one another with their tips and have the same refraction angles α , and has a telescopic objective 7 which emits radiation the laser emitter 1 is arranged behind the second lens cone. All optical elements are made of a material that is transparent to the laser radiation, for example quartz. The second cone lens 6 by means of laser radiation is arranged on the optical axis of this embodiment variant of the device so as to be adjustable by means of a stepping motor 8 and forms a panchromatic system with the former cone lens 5 . The telescopic lens 7 consists of a system of positive lenses 9 and a system of negative lenses I 0 , which are calculated for the smallest value of aberrations, and generally represents a telescopic system of variable magnification.

In Fig. 2 an embodiment of the device according to the invention for surgical treatment of ametropia is shown, in which the former 3 'of the radiation energy density distribution includes three with their base surfaces facing the laser emitter 1 and having the same refractive angle α cone lenses 5 , 11 and 12 and a telescopic lens 13 is mounted between the first and second conical lenses 5 and 11 by means of the radiation from the laser emitter 1 . In this embodiment variant of the device as well, all optical elements are made of material transparent to the laser radiation, for example quartz, while the second conical lens 11 is arranged to be adjustable along the optical axis by means of a stepping motor 8 by means of the laser radiation. The telescopic lens 13 is composed of a negative and a positive lens 14 and 15 , which are also calculated taking into account the smallest value of aberrations.

In Fig. 3 a further possible embodiment of the device for surgical treatment of ametropia is shown, in which the former 3 '' of the radiation energy density distribution also three with their base surfaces facing the laser emitter 1 cone lenses 5 , 11 and 16 and one between the first and second cone lens 5 , 11 ( Fig. 3) arranged in the way of the radiation of the laser emitter 1 , composed of a negative and a positive lens 14 or 15 ' , telescopic lens, the cone lens characteristics of which differ from those of the optical elements of the telescopic lens 13 ( Fig. 2) distinguish. In this embodiment variant, in contrast to the previous variant, the third cone lens 16 is designed with reverse conicity, the angle of refraction of which is equal to 90 ° - α , where a is the angle of refraction of the first and second cone lenses 5 and 11 by means of laser radiation. In this embodiment, all optical elements of the former 3 '' are also made of a material that is transparent to the laser radiation, for example quartz, while the second conical lens is arranged so that it can be adjusted along the path of the radiation from the laser lamp 1 along the optical axis by means of the stepping motor 8 .

The selection of one of the design variants of the Device according to the invention for surgical treatment of ametropia of the simplicity of their manufacture and of that Request the minimum value of aberrations in the optical system of the facility.

The device shown in Fig. 1 has a more compact design, but requires increased manufacturing accuracy and creates possible difficulties in its adjustment. The embodiment variants shown in FIGS. 2 and 3 enable increased accuracy when performing the operation, since they utilize merged radiation beams and are distinguished by the smallest possible aberration of the optical system.

The device shown in FIG. 3 has a more compact structure than the version shown in FIG. 2, but becomes much more complicated by using a conical lens 16 with reverse conicity in the manufacturing sense.

The facility for surgical treatment The ametropia works as follows.

The mode of operation of the device according to the embodiment variant from FIG. 1 will be explained on the basis of the treatment example of myopia.

As is known, the surface of the cornea of a normal eye can be described as a paraboloid with a radius of curvature R.

The surface of the cornea ( Fig. 4, 6) of the eye in myopia is also described as a paraboloid with a radius of curvature R _m at the apex smaller than in the case of a normal eye R _m < R .

In order to cure myopia, a dashed layer 17 delimited by two paraboloid surfaces of different curvature must be removed from the cornea 4 ( FIG. 4) of the eye. During myopia treatment, the parallel, cylindrical radiation beam 2 emerging from the laser emitter 1 ( FIG. 1) passes through the first conical lens 5 with a uniform distribution of the radiation energy density over the cross section of the circle with the diameter D , in which it forms a funnel-shaped radiation beam 18 with the wall thickness of the funnel (D / 2) cos β and the cone angle 2 β at the funnel tip, which result from the relationship with the refraction angle α and the refraction value n of the cone lens 5 :

As it continues, the radiation beam 18 deforms after it has passed through the cone lens 6 with the same refraction angle α to form a ring beam 19 with the wall thickness of the ring D / 2, the ring formed during this during a bumpless gradual adjustment of the second cone lens 6 by means of the stepping motor 8 also changes its outer diameter D ₁ gradually. In the relevant embodiment variant of the device, the regulation of the size D ₁ from the ring of the smallest diameter D ₂ (if the ring deforms into a circle with the inner ring diameter equal to 0) to the ring of the maximum size with the outer diameter D ₁ ^{max is} provided, the size D ₁ is connected to the adjustment of the cone lens 6 in the following relationship:

D ₁ = D + 2 l · tg β (2)

in the l the adjustment size of the conical lens 6 from its zero position (the position 6 ' on Fig. 1) means, in which D ₁ = D. It becomes D ₁ = D if the distance a between the tips of the conical lenses 5 and 6 is chosen according to the relationship:

where D ₀ diameter and L mean the strength of the conical lens 5 .

The equation is correct in the case of identical lenses 5 and 6 .

Behind the second cone lens 6 , the radiation beam 19 , which is a ring in cross section, passes through the telescopic lens 7 , in which it is deformed with the magnification coefficient K to form a likewise parallel, annular radiation beam 20 , the outer diameter D 2 and the wall thickness d of which are variable . This radiation beam 20 is directed directly onto the cornea 4 of the eye. Each change in the wall thickness d of the radiation beam 20 is achieved by gradually changing the distance between the lenses 9 and I 0 in the telescopic lens 7 .

In this way, D ₂ = D ₁ · K , where K is the magnification coefficient, where K <1, ie the cross section of the radiation beam 20 is from the ring with the largest possible diameter D ₂ = D ₁ ^max · K to the circle with the diameter D ₂ = D · K changes. The diameter D ₂ = D ₁ ^max · K is comparable to the diameter of the cornea 4 of the human eye.

The wall thickness d of the annular radiation beam 20 is selected on the basis of the conditions for performing the operation and on the basis of the characteristic values of the laser emitter 1 . It is desirable to choose the size d as small as possible, taking into account the diffraction values of the former 3 of the energy density distribution.

When utilizing the device according to the shown in the Fig. 2 embodiment for the treatment of myopia emerging from the laser emitter 1 parallel radiation beam 2 occurs with uniform distribution of the radiation energy density over the cross section with the diameter D as in the previous case by the first conical lens 5 through and is thereby converted into a funnel-shaped radiation beam 18 with the wall thickness of the funnel (D / 2) cos β and the angle 2 β at the cone tip of the funnel. Upon further passage through the system of spherical lenses I 4 and I 5 forming the telescopic objective 13 , the radiation beam I 8 deforms into an annular radiation beam 22 with a constant mean diameter and with decreasing wall thickness, the focal plane 21 of which intersects and closes the surface of the cornea 4 is perpendicular to the optical axis of the device.

Behind the telescopic lens 13, the annular radiation beam 22 passes through the telescopic, tapered system having a variable magnification through which 11 and 12 form the conical lenses in which there variable initially in a funnel-shaped radiation beam 23 and then in a ring-shaped radiation beam 24 diameter D ₂ is deformed with decreasing wall thickness d .

The smallest cross-section of the annular radiation beam 24 represents a circle with the diameter 2 d , the size d being selected on the basis of the conditions of the operation, the characteristic values of the laser emitter 1 and the former 3 ' . You choose the size as the minimum possible, it is mainly determined by diffraction characteristics of the former 3 ' . A change in the diameter D ₂ to the necessary value is achieved by the gradual adjustment of the cone lens 11 along the optical axis by means of the stepping motor 8 .

In the device according to the embodiment shown in FIG. 3, the mode of operation of the former 3 '' of the radiation energy density distribution differs from that of the former 3 ' according to FIG. 2 in that, according to the telescopic lens 13', the annular radiation beam 22 through the telescopic one , conical system passes through, which form the conical lenses 11 and I 6 , the latter of which is designed with reverse conicity, in which the bundle 22 is first in a funnel-shaped radiation beam 25 and then in the annular radiation beam 26 of variable diameter with decreasing in the direction of the radiation Wall thickness d is deformed.

The smallest cross section of this radiation beam also represents a circle with the diameter 2 d . A change in the characteristic values of the radiation beam 26 is also achieved here by a gradual adjustment of the cone lens 11 along the optical axis with the aid of the stepping motor 8 .

The former 3 '' from FIG. 3 has a more compact structure than the former 3 ' according to FIG. 2, since at the largest values of the diameter D ₂ ^max both annular radiation beams 24 ( FIG. 2) and 26 ( FIG . 3) against the cornea 4 of the eye are passed, the spacing c between the base surfaces of the telescopic, tapered system of the former 3 '' forming cone lenses 11 and 16 is always less than the spacing b between the bases of the truncated lenses 11 and 12 in the former 3 ' remains, ie the condition c < b is always met.

As is known, exposure to ultraviolet radiation on their biological tissues Ablation, evaporation, being in a certain range the radiation energy density is the thickness of the removal layer  is proportional to the energy density.

When the operation is carried out, the action of the radiation beam 20 ( FIG. 1) on the cornea 4 of the eye causes the layer 17 to be removed ( FIG. 4). Removal of the corresponding layer 17 ( FIG. 6) also occurs during the intervention of the radiation beams 24 ( FIG. 2) and 26 ( FIG. 3) on the cornea 4 of the eye. The irradiation begins in the central zone of the cornea 4 with a minimal bundle diameter and is carried out by shortening the irradiation time by increasing the diameter of the radiation intervention bundle. In accordance with the course of the irradiation process, a layer 17 ( FIGS. 4 and 6) of the cornea 4 is removed, which is delimited by two parabolic surfaces of revolution, one of which is the corneal surface deformed by the myopia and the other of which is the surface of the cornea 4 after exposure to the radiation of the laser emitter 1 ( Fig. 1, 2, 3). The irradiation is carried out until the myopia is eliminated (dashed layer 17 in FIGS. 4, 6).

The surface of the cornea of the eye in hypermetropia can be described as a paraboloid with a radius of curvature R _g at its tip greater than that of a normal eye R _g < R . To treat hypermetropia, a dashed layer 27 ( FIGS. 5 and 7) delimited by two parabolic rotation surfaces of different curvature must be removed from the cornea 4 . The treatment for hypermetropia is the same as for myopia, but with the difference that in the case of hypermetropia the irradiation of the cornea 4 starts from the circumference with a largest diameter of the radiation intervention bundle and is carried out with a reduction in both the diameter of the intervention bundle and the radiation duration .

For a better understanding of the nature of the present Invention is a specific embodiment below cited.

The device according to the invention for the surgical treatment of ametropia in the embodiment variant shown in FIG. 3 was completed and tested. To change the refraction of the eye of a rabbit, the radiation from an excimer laser emitter 1 of the molecules A + F with the wavelength 193 nm was used, which was combined to form a parallel, cylindrical radiation beam with a diameter of D = 6 mm. All fixed elements of the former 3 '' of the radiation energy density distribution are made of optical quartz (n = 1.559). The angle of refraction α reached 10 ° in the first cone lens 5 with the outward taper, while that of the third cone lens 16 with the reverse taper reached 90 ° - α = 76 °. These conical lenses are mounted immovably. The second cone lens 11 with the outward taper and the refraction angle α = I 4 ° was adjusted along a distance l = I 50 mm along the optical axis, which makes it possible to size D ₂ from 8 mm to 0.5 mm with a constant wall thickness of the radiation ring in the plane of engagement d = 0.25 mm = const.

The repetition frequency of the radiation pulses of the laser emitter 1 reached 15 Hz, the pulse energy changed from 100 to 300 mJ. In the operations performed on 16 eyes (8 rabbits), the change in the corneal refraction was achieved in a range from 0.5 to 5 dptr depending on the intervention values.

By using the device according to the invention are an 8 to 10-fold increase in accuracy in the formation of a predetermined Shape of the treatment area of the cornea, a 7- to 8 times abbreviation of the duration of the operation in comparison with the establishment of a similar purpose interchangeable aperture and 3 to 4 times Abbreviation achieved in comparison with the facility in which the shaper of the radiation energy density distribution designed as an optical chamber is.

An increase in the manufacturing accuracy of the prescribed shape of the treatment area of the cornea is mainly achieved by significantly reducing the duration of the surgical operation. This shortening of the duration of the execution of the surgical operation is brought about by the fact that at all times the entire radiation emerging from the laser emitter 1 acts on the treatment surface of the cornea 4 .

Claims (5)

1. Device for the surgical treatment of ametropia, which provides a pulsed laser emitter ( 1 ) of the ultraviolet region and a shaper ( 3 ) arranged in the way of its radiation beam and providing the distribution of the radiation energy density over the cross section of the radiation beam, characterized in that the shaper ( 3 ) Radiation energy density distribution of the laser emitter ( 1 ) across the cross section of the radiation beam is an optical system that consists of at least two conical lenses ( 5, 6 ) attached to an optical axis and a telescopic lens ( 7 ) and the parallel cylindrical radiation beam ( 2 ) of the laser beam ( 1 ) can deform into a ring-shaped radiation beam ( 20 ) of variable diameter, the maximum value of which is comparable to the diameter of the cornea ( 4 ) of the human eye. 2. Device for the surgical treatment of ametropia according to claim 1, characterized in that the former ( 3 ) of the radiation energy density distribution provides two cone lenses ( 5, 6 ) facing one another with their tips facing the same refraction angle ( α ), while the telescopic lens ( 7 ) is mounted behind the second conical lens ( 6 ) by means of radiation. 3. A device for the surgical treatment of ametropia according to claim 1, characterized in that the former ( 3 ' ) of the radiation energy density distribution provides three conical lenses ( 5, 11, 12 ) with their base surfaces facing the laser emitter ( 1 ), one of which by way of radiation the second and the third cone lens have the same refraction angles, while the telescopic lens ( 13 ) is mounted between the first and the second cone lens ( 5 and 11 ) by means of the radiation from the laser emitter ( 1 ). 4. A device for the surgical treatment of ametropia according to claim 1, characterized in that the former ( 3 '' ) of the radiation energy density distribution contains three cone lenses ( 5, 11, 16 ) facing the laser emitter ( 1 ), the telescopic lens ( 13 ') between the first and second cone lens (5, 11) mounted in the path of the radiation of the laser emitter (1), wherein by way of radiation of the laser emitter (1) the third cone lens (16) is carried out with the reverse taper and the angle of refraction 90 ° - α is where α means the angle of refraction by means of the radiation from the second cone lens ( 11 ). 5. A device for the surgical treatment of ametropia according to claim 1, 2, 3 or 4, characterized in that the second conical lens ( 6 or 11 ) along the optical axis is adjustably mounted along the path of the radiation from the laser emitter ( 1 ).