JPH07265350A - Laser operation apparatus - Google Patents

Abstract

PURPOSE:To achieve a correction of far sighting with a reduction in the radius of curvature of a cornea by excising the cornea in a shape of a convex lens with a simple structure even when a number of masks and apertures are not prepared varying in the preoperation radius of curvature of the cornea and the correction diopter. CONSTITUTION:A laser operation apparatus which corrects abnormality in refraction by abrasion of a cornea has apertures 4 and 5 with a variable diameter of aperture, a light shielding means allowing the changing of a light shielding area at the central part of a laser beam, a control means to control the light shielding means and the apertures 4 and 5 and a beam rotation means to turn the axis of the laser beam. This enables the changing of the shape of the laser beam passing through the apertures 4 and 5 and the light shielding means to accomplish a correction of far sighting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser surgical apparatus for correcting the refractive error by correcting the cornea, and in particular, it corrects hyperopia by reducing the corneal curvature of the hyperopic eye to increase the refractive power. The present invention relates to a laser surgery device that can perform

[0002]

2. Description of the Related Art In recent years, a technique (Photo-refractive Keratectomy) has been attracting attention in which the surface of the cornea is removed by a laser beam and the curvature of the cornea is changed to correct the refractive error of the eyeball. However, currently, only myopia correction is performed, and almost no hyperopia correction is performed. The reason is as follows. As shown in Fig. 1, myopia can be corrected by cutting the central part of the cornea deep and the peripheral part shallow to form a convex lens. Therefore, the ablation area of the laser can be changed by using a normal circular variable aperture. Can be done relatively easily. On the other hand, in hyperopic correction, as shown in FIG. 2, it is necessary to cut the central part shallow and the peripheral part deep and form a concave lens. Therefore, the central part of the laser beam is blocked by a circular aperture, and the This is because it is necessary to do something difficult with a normal aperture of changing size.

In order to perform this difficult aperture control, several methods have been proposed so far. Tokuhei 4-
No. 33220 (GB 8606821) "Shaping of surface using laser" (Applicant Summit), a method of using a special mask to ablate the peripheral part deeper than the central part and cut it into a concave lens shape. Are shown (see FIG. 3). The mask used in this method has a predetermined shape (profile) resistance to laser light, which shape is created by varying the thickness or texture of the mask material. When the cornea is irradiated with a laser beam through this mask, a part of the laser beam is selectively absorbed, and the other part is transmitted to the corneal surface according to the shape of this mask to selectively select the surface. Ablation. By forming the mask for hyperopia correction so that the central portion absorbs much and the transmittance decreases, and the peripheral portion absorbs less and increases the transmittance, the cornea can be excised in a concave lens shape.

Further, JP-A-64-86968 (FR
8708963) "Apparatus for performing corneal surgery on the eye" (Applicant IBM) shows a cutting method of irradiating a laser while rotating or translating a robe-shaped aperture. (See Figure 4). The robe-shaped aperture used in this method has a predetermined shape.
Corneal ablation is performed by intermittently superimposing a lot of laser beam lobes by a cha, and as a result, the ablation necessary for refractive correction is ablated to change the corneal curvature. . Therefore, in the hyperopic correction aperture, the portion corresponding to the peripheral portion of the cornea is wider than the central portion of the cornea, so that the peripheral portion is ablated more.

Japanese Patent Application Laid-Open No. 2-84955 (SU 445777) is known as a device similar to Japanese Patent Application Laid-Open No.
2) "Apparatus for correcting eye refractive error" (Applicant
It is also found in the Mesotras Levo Nautino-Tev-Czechski Complex "Microhil Lugia Graza").

[0006]

However, these hyperopia correction methods have the following drawbacks. In the former method using a special mask, the shape of the mask changes depending on the corneal curvature of the eyeball to be corrected and the correction power,
Masks with different shapes are required for preoperative corneal curvature and correction power, and a large number of mask shapes must be prepared. Also, since the amount of corneal resection for correction depends on the mask shape, the accuracy of the mask shape is an important factor,
Accordingly, there is a drawback that manufacturing becomes difficult.

In the latter method of displacing the lobe image, the shape of the lobe-shaped aperture changes depending on the corneal curvature before correction and the correction degree as in the above case.
There is a drawback that the number of types of tea is very large.

In view of the above-mentioned drawbacks, an object of the present invention is to perform a laser operation for refraction correction capable of correcting hyperopia by reducing corneal curvature with a simple structure without preparing a large number of masks and apertures. To provide a device.

[0009]

In order to achieve the above object, the device of the present invention has the following features.

(1) In a laser surgical apparatus for correcting a refractive error by ablating the cornea with a laser beam, a circular aperture having a variable aperture diameter and an aperture diameter of the circular aperture. Changing aperture driving means, projecting means for projecting the circular aperture onto the cornea, beam rotating means for rotating the laser beam, and laser beam passing through the circular aperture. -A light-shielding plate for limiting the beam, a light-shielding plate moving means for changing the distance of the light-shielding plate from the rotation axis of the beam rotating means, the aperture driving means, a beam rotating means, and a light-shielding plate movement It is characterized by comprising a control means for controlling the means to perform hyperopia correction.

(2) The light shielding plate of (1) is characterized in that it has a light shielding edge which is orthogonal to the radius of the opening of the circular aperture.

(3) In the laser operation apparatus according to (1), the laser is an excimer laser, and a beam whose light amount distribution on the beam cross section moves in the Gaussian direction Moving means, the control means responding to the movement of the laser beam by the beam moving means, the circular aperture.
It is characterized by controlling the size of the opening of the tea.

(4) The circular aperture of (1) also serves as an aperture for correcting myopia, and during correction of myopia, the light shielding plate moving means moves the light shielding plate to the outside of the optical path.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (Overall Optical System) FIG. 5 is a layout diagram of an optical system of an embodiment. Reference numeral 1 is a laser light source, and an excimer laser is used in the embodiment. The laser beam emitted from the laser light source is reflected by Mira-2 and Mira-3. The mirror 3 is movable in the direction of the arrow, and is uniformly ablated by scanning the laser beam in the direction having a non-uniform intensity distribution described later during myopia correction. In this respect, Japanese Patent Application No. 2
No. 416767 (ablation device by title of invention laser beam) is described in detail. By moving the mirror 3 in the direction of the arrow, the optical axis of the laser beam emitted from the laser light source 1 is displaced from the rotation axis L of the image rotor 6.

Reference numeral 4 denotes a flat plate aperture which is movable in a plane perpendicular to the rotation axis L, and the aperture 4 defines a region where the laser beam passes through the aperture 5. The aperture 4 has a light-shielding edge orthogonal to the radius of the aperture of the aperture 5, but it is not always necessary. Figure 6 shows
It is the figure which looked at the cha 4 and the aperture 5 from the side surface. The aperture 4 escapes out of the optical path during myopia correction and is inserted into the optical path during hyperopia correction. The aperture 5 is a circular aperture whose opening diameter is variable. The aperture 4 is arranged close to the aperture 5, and the aperture 5 is at a position conjugate with the cornea 9 with respect to the projection lens 7. Therefore, a beam-shaped image on the aperture is formed on the cornea 9.

The laser beam which has passed through the apertures 4 and 5 passes through the image lens 6 and the projection lens 7 and is bent 90 ° by the plane mirror 8 to form the cornea 9. To reach. The image rotor 6 is a projection lens 7
It may be arranged between the cornea 9 and the cornea 9.

Reference numeral 10 is an optical system of a binocular surgical microscope, and the observation optical axes on the left and right are positioned so as to sandwich the plane mirror 8. Since various commercially available binocular observation optical systems are available and the configuration itself is not related to the present invention,
This is omitted. (Function of optical system in hyperopia correction)

The shape of a typical cross section of the exit beam of the excimer laser is shown in FIG. 7, and the intensity distribution is almost uniform in the horizontal direction (x-axis direction) of the beam and in the vertical direction (y-axis direction). direction)
Has a Gaussian distribution. FIG. 8 shows a state in which the aperture 4 is escaped from the optical path as seen from the laser light source side. The beam deviated from the rotation axis L of the image rotor 6 by the mirror 3 in the Y direction by f is cut at the peripheral portion by the aperture 5 having the opening diameter d, and the hatched portion is left. Only the beam passes through the aperture 5. The laser beam in the shape of the shaded portion is projected onto the cornea 9 by the projection lens 7 to ablate the cornea. The laser beam is rotated by the image rotor 6 to rotate and move the abrasion region. When shots are repeated while changing the rotation angle of the laser beam, the corneal surface is ablated into a ring shape as shown in FIG. 9 (a), and the cross section at that time is shown in FIG. 9 (b). For example, the rotation angle of the beam is set to 30 degrees, and shots from 12 directions are overlapped.

The amount of deviation f of the laser beam from the axis L
When the aperture diameter d of the aperture 5 is changed correspondingly,
The ablation area changes. As shown on the left side of FIG. 10, the deviation amount f of the laser beam from the axis L is f1, f
2 ... Fn, the aperture diameter d of the aperture 5 is changed to d1, d2 ...
When the laser beam is enlarged to dn from the stage where the laser beam passes the axis L, the corneal cross section is gradually excised from the center to the outside as shown in the right side of FIG. Sablation is achieved. The rotation angle should be determined in consideration of the required surface accuracy, ablation rate, etc., but when f is large, it is better to reduce the rotation angle once. The surface becomes smooth.

When the laser beam shift amount f and the aperture diameter d of the aperture 5 are ablated as described above, as shown in FIG. 11, the aperture 4 is image-rotated. The laser beam 6 is inserted into the optical path of the laser beam so as to shield it from the rotation axis L to the distance e. At this time, the ablation shape of the cornea has a diameter 2e at the center as shown in FIG.
A substantially circular non-ablated region is formed (the projection lens has a projection magnification of 1 for simplicity).

Therefore, by changing the distance e from the rotation axis L of the image rotor 6 which is shielded by the aperture 4, the diameter 2e of the central circular region which is not ablated is changed to sequentially ablate. As shown in FIG. 2, an ablation is performed in the shape of a concave lens having a shallow central portion and a deep peripheral portion to correct a hyperopic eye.

The operation of the apparatus having the above configuration will be briefly described. The operator observes the surgical microscope and fixes the cornea of the surgical eye in place with respect to the device. The ablation region and its shape are determined according to a program stored in the control device based on the data such as the refractive power of the surgical eye which is input in advance to the data input device, and the operation of the device is thereby determined. To control.

In the case of myopia correction, the aperture 4 is moved out of the optical path by a driving mechanism such as a motor. The laser beam is limited by the aperture 5, and the mirror 3 is sequentially moved to scan the laser beam in a direction having a non-uniform intensity distribution, thereby cutting the laser beam into a uniform circle. . Aperture 5
Abrasion is performed as shown in FIG. 1 by sequentially changing the size of.

In the case of hyperopia correction, the aperture 4 is inserted in the optical path. The amount of movement of the mirror-3 (the amount of deviation f from the axis L), the opening diameter d of the aperture 5, the image rotor 6
The hyperopia correction is performed by controlling the rotation angle and the position of the aperture 4 (distance e from the axis L) according to a program.

In the above embodiment, the laser beam is kept in a state in which the deviation amount f of the laser beam from the rotation axis L is kept constant.
Rotate the beam 360 degrees to change f and the opening diameter d, etc., and repeat the procedure. After scanning the laser beam while changing the opening diameter d of the aperture 5, the laser beam This may be repeated by changing the rotation angle.

Further, in the above description, controlling the opening diameter d of the aperture 5 together with the deviation amount f of the laser beam from the rotation axis L is achieved by superimposing ring-shaped ablation well. This is for the purpose of making the application area substantially uniform, and may be omitted if not necessary. The number of shots to be overlapped to perform one ring-shaped ablation also changes with the deviation amount f if necessary. Is also good.

Further, when the beam quantity is expanded to an appropriate size by using a filter or the like to make the light quantity distribution uniform, it is not necessary to move the laser beam.

[0028]

According to the present invention, the curvature of the cornea can be obtained by cutting the cornea into a concave lens shape by a simple mechanism without preparing a large number of masks and apertures which differ depending on the preoperative corneal curvature and the correction power. By reducing the radius, it becomes possible to correct hyperopia.

[Brief description of drawings]

FIG. 1 is a diagram showing a cut portion of a cornea of an eye to be corrected for myopia.

FIG. 2 is a view showing a cut portion of a cornea of an eye to be examined for correcting hyperopia.

FIG. 3 is a diagram showing an example of an ablation method in which aperture control for hyperopia correction is performed.

FIG. 4 is a diagram showing another example of an ablation method in which aperture control for hyperopia correction is performed.

FIG. 5 is a layout diagram of an optical system of the present embodiment.

6 is a side view of the aperture 4 and the aperture 5. FIG.

FIG. 7 is a view showing the shape of a typical cross section of an exit beam of an excimer laser.

FIG. 8 is a view showing a state in which the aperture 4 is made to escape from the optical path.
It is the figure seen from the light source side.

FIG. 9 is a diagram showing an abraded state of the cornea when the laser beam is rotated and the ablation region is rotationally moved.

FIG. 10 is a diagram showing a change in the abrasion region when the deviation amount f of the laser beam from the axis L and the aperture diameter d of the aperture 5 are changed in association with each other.

FIG. 11 is a view showing a state in which the aperture 4 is shielded from the rotation axis L of the image rotor 6 up to a distance e.

FIG. 12 is a diagram showing an ablation shape of the cornea in FIG. 11.

[Explanation of symbols]

 1 Laser Light Source 3 Mirror 4,5 Aperture 6 Image Rotor

Claims (4)

[Claims] 1. A laser surgical apparatus for ablating a cornea with a laser beam to correct a refractive error, a circular aperture having a variable opening diameter, and an opening diameter of the circular aperture. Aperture driving means for changing, projection means for projecting the circular aperture onto the cornea, beam rotating means for rotating the laser beam, and laser beam passing through the circular aperture. A light-shielding plate for limiting the beam, a light-shielding plate moving means for changing the distance of the light-shielding plate from the rotation axis of the beam rotating means, the aperture driving means, the beam rotating means, and the light-shielding plate moving means. A laser surgical apparatus, comprising: a control unit for controlling the hyperopic correction. 2. The laser surgical apparatus according to claim 1, wherein the shading plate has a shading edge which is orthogonal to a radius of the opening of the circular aperture. 3. The laser operating apparatus according to claim 1, wherein the laser is an excimer laser, and the beam movement is such that the light quantity distribution of the beam cross section moves the laser beam in the Gaussian direction. Means for controlling the size of the opening of the circular aperture in response to the movement of the laser beam by the beam moving means. . 4. The circular aperture according to claim 1 also serves as an aperture for correcting myopia, and the light-shielding plate moving means moves the light-shielding plate outside the optical path when correcting myopia. The surgical device.