JPH07265349A - Cornea laser operation apparatus - Google Patents

Abstract

PURPOSE:To obtain a laser operation apparatus for correcting refraction which enables the correction of far sighting by arranging a second aperture at a position where the outer circumference of a beam passing when a first aperture with a variable aperture diameter has a specified diameter crosses on an optical axis with an optical element to reduce the radius of curvature of a cornea with a simple structure. CONSTITUTION:A circular aperture 2 with a variable aperture diameter is formed and an axial contact lens 3 has a conical prism surface with the apex thereof placed on an optical axis. An outer circumference part of a laser beam passing through the aperture 2 turns to an inner circumference part of the beam separated in a ring with the axial contact lens 3 and the center part of the beam from the aperture 2 turns to an outer circumference part of the beam separated in a ring state. A second circular aperture 4 with a variable aperture diameter is placed at a point A position where a luminous flux passing the outermost circumference of the aperture 2 is bent with the axial contact lens 3 to cross the optical axis when the opening of the aperture 2 reaches the maximum thereof with respect to the aperture 2 and the axial contact lens 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corneal laser operating apparatus for correcting corneal refractive error, and more particularly to an apparatus capable of performing hyperopic correction for reducing the corneal curvature radius of a hyperopic eye.

[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 make the central part shallow and the peripheral part deep so as to excise it into a concave lens shape. Therefore, the center of the laser beam is interrupted by a circular aperture. Moreover, it is necessary to do something difficult with a normal aperture that changes its 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 is made 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. The mask for hyperopia correction is formed so that the central portion absorbs a large amount of light and the peripheral portion absorbs a small amount of light, and the peripheral portion has a large amount of light absorption.

Further, JP-A-64-86968 (FR
8708963) "Apparatus for performing corneal surgery on the eye" (Applicant IBM) shows an apparatus for irradiating a laser while rotating or translating a robe-shaped aperture. (See FIG. 4). The robe-shaped aperture used in this method has a predetermined shape, and a large number of lobe images of the laser beam due to this aperture are intermittently superposed to perform corneal ablation. As a result, the ablation amount necessary for refractive correction is ablated to change the curvature of the cornea. 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. Further, since the amount of corneal resection for correction depends on the mask shape, the accuracy of the mask shape is an important factor, and there is a drawback that the 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 operation apparatus for correcting a refractive error by ablating the cornea with a laser beam, an optical element having a conical prism surface arranged on the optical axis and an opening. A first aperture having a variable aperture and a second aperture arranged at a position where the outer circumference of a beam passing when the first aperture has a predetermined diameter intersects on the optical axis by the optical element.
Aperture, a projection lens for projecting the second aperture onto the cornea of the surgical eye, drive means for changing the aperture diameter of the first aperture, and control for controlling the drive of the drive means. Means for correcting hyperopia by changing the shape of the laser beam passing through the first aperture.

(2) The corneal laser surgery apparatus according to (1) further has a drive means for changing the opening diameter of the second aperture and a control means for controlling the drive of the drive means. The feature is that the diameter of the ablation region can be changed.

(3) The control means of (2) is characterized by including a program storage means for correcting myopia.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a schematic diagram of the optical system layout of the device of the present invention.

Reference numeral 1 denotes a laser beam for ablating the corneal surface, which is emitted from a laser light source. In this embodiment, an excimer laser having a wavelength of 193 nm is used. Reference numeral 2 is a first circular aperture with a variable opening diameter. Although the optical system from the laser light source to the circular aperture 2 is omitted, an expander for expanding the beam, a correction optical system for correcting the light quantity distribution, and a mirror for reflecting the beam are arranged. It Reference numeral 3 denotes a conical axicon lens, and the axicon lens 3 has a conical prism surface, and its apex is placed on the optical axis. The beam passing through the axicon lens 3 is bent inward by its prism surface, intersects once, and then is separated into an annular shape so that the central part thereof is removed. That is, the outer peripheral portion of the laser beam that has passed through the aperture 2 becomes the inner peripheral portion of the beam that is annularly separated by the axicon lens 3, and the center of the beam from the aperture 2 is formed. The portion becomes the outer peripheral portion of the beam separated into an annular shape.

Numeral 4 is a second circular aperture having a variable opening diameter, like the aperture 2. Aperture 4 is an aperture
With respect to the aperture 2 and the axicon lens 3, when the aperture of the aperture 2 is maximized, the light flux passing through the outermost circumference of the aperture 2 is bent by the axicon lens 3 and crosses the optical axis at a position A. Placed in. A projection lens 5 makes the aperture 4 and the cornea 6 conjugate. Therefore, although the size of the projection lens 5 is changed depending on the magnification of the projection lens 5 to change its size, an image having the same shape as the beam-shaped image on the aperture 4 is formed on the cornea 6.

The aperture 2 and the axicon lens 3
When performing myopia correction, the aperture 2 may be placed in the maximum aperture state and the aperture diameter of the aperture 4 may be controlled as is known in the radiological ablation.
Alternatively, the aperture diameter of the aperture 4 may be controlled after moving the aperture 2 and the axicon lens 3 out of the optical path.

Hyperopic correction using an apparatus having the above optical system will be described. The operation eye is placed at a predetermined position with respect to the laser device by an alignment mechanism (not shown). De-
A first aperture drive device and a second aperture drive device based on input information for determining the ablation amount input to the input device.
The laser beam is irradiated onto the surgical eye while the aperture diameters of the aperture 2 and the aperture 4 are controlled by the aperture driving device.

In order to ablate the surgical eye as shown in FIG. 2, the diameter of the aperture 4 is adjusted by the second aperture drive device so that the outer diameter of the laser beam is outside the ablation area of the cornea. Adjust to match the diameter.

The laser beam 1 emitted from the laser light source is
Although it passes through the aperture 2 and the axicon lens 3 to reach the aperture 4, the aperture 2 is set to the maximum opening and ablation is started. As described above, since the outermost peripheral light on the aperture 2 passes through the point A which is the center of the aperture 4, the beam shape on the aperture 4 is not separated, and is uniform as shown in FIG. It becomes a round shape. The beam shape on the aperture 4 is projected onto the cornea 6 by the projection lens 5, and the cornea 6 is ablated into a uniform circle.

Next, the controller repeats ablation while sequentially changing the opening of the aperture 2 according to a program determined based on the correction power and the outer diameter of the ablation area of the cornea. When the diameter of the aperture 2 is reduced by the first aperture driving device as shown in FIG. 7, the outermost light on the aperture 2 is in front of point A (on the laser light source side).
And the beam shape on the aperture 4 is a circular shape with the center part missing out as shown in FIG. 8, and the beam shape on the aperture 4 is projected onto the cornea by the projection lens 5. Therefore, the cornea 6 is ablated into a ring shape,
The central part becomes a non-ablation area.

When the ablation is performed while the aperture diameter of the aperture 2 is gradually reduced from the maximum diameter, the abraded area in the central portion is changed from the ablated state as shown in FIG. The beam gradually spreads, and finally the beam does not pass through the aperture of the aperture 4 and is not abraded. As a result, the cornea 6 is shown in FIG.
As described above, the ablation is performed in the shape of a concave lens having a shallow central portion and a deep peripheral portion to correct the hyperopic eye.

Although the aperture diameter of the aperture 2 is changed from large to small in the above embodiment, it may be changed from small to large.
Further, by adjusting the opening diameter of the aperture 4, it is possible to smooth the boundary between the ablated portion and the non-ablated portion on the outer circumference.

Further, in the embodiment, the correction optical system for correcting the spreader and the light quantity distribution is used. However, the present inventor has filed Japanese Patent Application No. 2-416767 (filed Dec. 28, 1990; -Ablation device based on
It can also be applied to the scanning method as proposed in.

[0024]

According to the present invention, the cornea can be cut into a concave lens shape by a simple mechanism to reduce the corneal curvature by a simple mechanism without preparing many masks and apertures which differ according to the preoperative corneal curvature and the correction power. It is possible to reduce the size and 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 schematic diagram of an optical system layout of the apparatus of the embodiment.

FIG. 6 is a view showing a beam shape on the aperture 4 when the aperture 2 is set to the maximum opening.

FIG. 7 is a diagram showing a state of a beam when the diameter of the aperture 2 is reduced.

FIG. 8 is a view showing a beam shape on the aperture 4 when the diameter of the aperture 2 is reduced.

[Explanation of symbols]

 1 Laser Beam 2 Aperture 3 Axicon Lens 4 Aperture 5 Projection Lens 6 Corneal

Claims (3)

[Claims] 1. A laser surgical apparatus for correcting a refractive error by ablating a cornea with a laser beam, an optical element having a conical prism surface arranged on an optical axis, and an aperture diameter. Of the variable aperture and a second aperture arranged at a position where the outer circumference of the beam passing when the first aperture has a predetermined diameter intersects on the optical axis by the optical element. -A projection lens for projecting the second aperture onto the cornea of the surgical eye, a driving means for changing the opening diameter of the first aperture, and a control means for controlling the driving of the driving means. , And a laser beam passing through the first aperture.
A corneal laser surgery device, which corrects hyperopia by changing the shape of a cornea. 2. The corneal laser surgery apparatus according to claim 1, further comprising drive means for changing the opening diameter of the second aperture and control means for controlling the drive of the drive means, and the corneal abrasion apparatus is provided. -A corneal laser surgery device characterized by being able to change the diameter of the operation area. 3. The corneal laser surgery apparatus according to claim 2, wherein the control means includes a program storage means for correcting myopia.