JP3580851B2 - Corneal laser surgery device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a corneal laser surgical device for correcting a corneal refractive error, and more particularly, to a device for performing hyperopia correction for reducing the radius of corneal curvature of a hyperopic eye.
[0002]
[Prior art]
2. Description of the Related Art In recent years, attention has been paid to a technique (Photo-refractive Keratectomy) for correcting a refractive error of an eyeball by ablating a surface of a cornea with a laser beam and changing a curvature of the cornea. However, currently, only myopia correction is performed, and hyperopia correction is hardly performed. The reason is as follows. To correct myopia, as shown in FIG. 1, the central part of the cornea can be cut deep and the peripheral part can be cut shallowly in the form of a convex lens. Therefore, it is necessary to change the laser abrasion area using a normal circular variable aperture. Relatively easily. On the other hand, in hyperopia correction, as shown in FIG. 2, the central portion must be shallow, the peripheral portion must be deep, and the lens must be cut into a concave lens shape. Therefore, the center of the laser beam is interrupted by a circular aperture. Moreover, it is necessary to perform a difficult operation with a normal aperture of changing the size.
[0003]
Several methods have been proposed to date for performing this difficult aperture control. Japanese Patent Publication No. 4-33220 (GB 8606821) "Shaping the surface using a laser"(Applicant's Summit) uses a special mask to deeply ablate the periphery from the center to form a concave lens. A method of excision is shown (see FIG. 3). The mask used in this method has a predetermined shape (profile) resistance to laser light, which is created by changing the thickness or texture of the mask material. When the cornea is irradiated with the laser beam through the 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 the mask, and the surface is selectively absorbed. Abbreviation The mask for correcting hyperopia is formed such that absorption is large at the center and transmission is small, and absorption is small at the periphery and transmission is high.
[0004]
Japanese Unexamined Patent Application Publication No. 64-86968 (FR 8708963) entitled "Apparatus for performing corneal surgery on the eye" (applicant IBM) discloses a laser-shaped aperture while rotating or translating a laser. An apparatus for irradiating the laser is shown (see FIG. 4). The lobe-shaped aperture used in this method has a predetermined shape, and a corneal ablation is performed by intermittently superimposing a large number of laser beam lobe images by this aperture. As a result, the ablation required for the refractive correction is ablated to change the curvature of the cornea. Therefore, the aperture for correcting hyperopia is wider at the portion corresponding to the peripheral portion of the cornea than at the central portion of the cornea, so that the peripheral portion is more abraded.
[0005]
Japanese Patent Application Laid-Open No. 2-89555 (SU4457772), "Apparatus for Correcting Refractive Defects in the Eye" (Applicant: Mezzotraslevoy Nautino-Teff-Czechski Complex, "Microhillir Gear"・ Graza ”) is also available.
[0006]
[Problems to be solved by the invention]
However, these methods for correcting hyperopia have the following disadvantages.
In the former method of using a special mask, the shape of the mask differs depending on the corneal curvature and the correction power of the eye to be corrected.Therefore, masks having different shapes are required for the corneal curvature and correction power before surgery. Therefore, a large number of mask shapes must be prepared. In addition, since the correction corneal ablation amount depends on the mask shape, the accuracy of the mask shape is an important factor, and there is a drawback that manufacturing is difficult.
[0007]
In the latter method of displacing the lobe image, the shape of the lobe-shaped aperture changes depending on the corneal curvature and the correction power before correction, as in the above case. There is a disadvantage that the number becomes very large.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a laser surgery apparatus for refraction correction that can reduce corneal curvature and correct hyperopia with a simple structure without preparing a large number of masks and apertures. Is to do.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the device of the present invention has the following features.
[0010]
(1) In 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 are variable. A first aperture, and a second aperture disposed at a position where the outer periphery of a 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 unit for changing an opening diameter of the first aperture, and a control unit for controlling the driving of the driving unit. The present invention is characterized in that hyperopia is corrected by changing the shape of the laser beam passing through the first aperture.
[0011]
(2) The corneal laser surgical apparatus according to (1) further includes a driving unit for changing an opening diameter of the second aperture, and a control unit for controlling the driving of the driving unit, and the corneal abrasion is performed. It is characterized in that the diameter of the region can be changed.
[0012]
(3) The control means of (2) includes a myopia correction program storage means.
[0013]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a schematic view of the arrangement of the optical system of the apparatus of the present invention.
[0014]
Reference numeral 1 denotes a laser beam for ablating and 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 denotes a first circular aperture having 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 amount distribution, and a mirror for reflecting the beam are arranged. You. Reference numeral 3 denotes a conical axicon lens, and the axicon lens 3 has a conical prism surface and its vertex is located on the optical axis. The beam passing through the axicon lens 3 is bent inward by the prism surface and once intersects, and then is separated into an annular shape so that the central portion is removed. That is, the outer peripheral portion of the laser beam passing through the aperture 2 becomes the inner peripheral portion of the beam which is annularly separated by the axicon lens 3, and the center of the beam from the aperture 2 is formed. The portion is the outer periphery of the beam that is separated into an annular shape.
[0015]
Reference numeral 4 denotes a second circular aperture whose opening diameter is variable similarly to the aperture 2. When the aperture of the aperture 2 is maximized with respect to the aperture 2 and the axicon lens 3, the light beam passing through the outermost periphery of the aperture 2 is bent by the axicon lens 3. It is placed at the point A that intersects the optical axis. Reference numeral 5 denotes a projection lens, which makes the aperture 4 and the cornea 6 conjugate. Therefore, although the size of the projection lens 5 is enlarged or reduced depending on the magnification, the size of the image changes, but an image having the same shape as the beam shape image on the aperture 4 is formed on the cornea 6.
[0016]
When correcting myopia, the aperture 2 and the axicon lens 3 are placed in a state where the aperture 2 is at the maximum aperture, and the aperture diameter of the aperture 4 is controlled as is well known in the art. 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.
[0017]
The correction of hyperopia using the apparatus having the above-described optical system will be described.
The surgical eye is placed at a predetermined position with respect to the laser device by an alignment mechanism (not shown). The aperture diameters of the apertures 2 and 4 are determined by the first aperture driving device and the second aperture driving device on the basis of input information for determining the amount of abrasion input to the data input device. The laser beam is irradiated to the surgical eye while controlling the operation.
[0018]
In order to ablate the surgical eye as shown in FIG. 2, the diameter of the aperture 4 is adjusted by the second aperture driving device so that the outer diameter of the laser beam matches the outer diameter of the abrasion region of the cornea. Adjust to
[0019]
The laser beam 1 emitted from the laser light source passes through the aperture 2 and the axicon lens 3 and reaches the aperture 4, but the aperture 2 is set to the maximum aperture and the abrasion is performed. Start. As described above, since the outermost peripheral light on the aperture 2 passes through the point A which is the center on the aperture 4, the beam shape on the aperture 4 does not separate and is uniform as shown in FIG. It becomes a perfect circle. The beam shape on the aperture 4 is projected onto the cornea 6 by the projection lens 5, and the cornea 6 is shaped into a uniform circular shape.
[0020]
Next, the controller repeats the abrasion while sequentially changing the aperture of the aperture 2 according to a program determined based on the correction power and the outer diameter of the abrasion region 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 peripheral light on the aperture 2 intersects before point A (on the side of the laser light source), and The beam shape on the aperture 4 becomes a ring shape as shown in FIG. 8 with the central portion falling out in a circular shape, and the beam shape on the aperture 4 is projected onto the cornea by the projection lens 5. Abrasion is performed in a ring shape, and a central portion is a non-ablation region.
[0021]
When the abrasion is performed while the opening diameter of the aperture 2 is gradually reduced from the maximum diameter, the non-abraded area at the center gradually widens from the state where all the abrasion is performed as shown in FIG. Eventually, the beam will not pass through the aperture of the aperture 4 and will not be abraded. As a result, as shown in FIG. 2, the cornea 6 is abraded into a concave lens shape having a shallow central portion and a deep peripheral portion, thereby correcting the hyperopic eye.
[0022]
The aperture diameter of the aperture 2 is changed from large to small in the above embodiment, but may be changed from small to large. Further, by adjusting the opening diameter of the aperture 4, the boundary between the abraded portion and the non-ablated portion on the outer periphery can be made smooth.
[0023]
Further, in this embodiment, an expander and a correction optical system for correcting the light amount distribution are used. However, the present inventor has filed a Japanese Patent Application No. 2-416767 (filed on Dec. 28, 1990). Abrasion device).
[0024]
【The invention's effect】
According to the present invention, it is possible to reduce the corneal curvature by removing the cornea into a concave lens shape by a simple mechanism without preparing a large number of masks and apertures different for each of the preoperative corneal curvature and the correction power. Correction can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a resected part of a cornea of a subject's eye for correcting myopia.
FIG. 2 is a diagram showing a resected portion of a cornea of a subject eye for correcting hyperopia.
FIG. 3 is a diagram illustrating an example of a resection method in which aperture control for correcting hyperopia is performed.
FIG. 4 is a diagram showing another example of a resection method in which aperture control for correcting hyperopia is performed.
FIG. 5 is a schematic view of an optical system arrangement 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 aperture.
FIG. 7 is a diagram showing a beam state when the diameter of the aperture 2 is reduced.
FIG. 8 is a diagram showing a beam shape on the aperture 4 when the diameter of the aperture 2 is reduced.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 laser beam 2 aperture 3 axicon lens 4 aperture 5 projection lens 6 cornea

Claims (3)

In 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 disposed on an optical axis and a first element having a variable aperture diameter. An aperture, and a second aperture arranged at a position where the outer periphery of a 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 unit for changing an opening diameter of the first aperture, and a control unit for controlling the driving of the driving unit. A corneal laser surgical apparatus characterized in that hyperopia is corrected by changing the shape of the laser beam passing through the first aperture. The corneal laser surgical apparatus according to claim 1, further comprising a driving unit for changing an opening diameter of the second aperture, and a control unit for controlling the driving of the driving unit, wherein a diameter of an abrasion region of the cornea is provided. A corneal laser surgery apparatus characterized in that the corneal laser operation apparatus can be changed. 3. A corneal laser surgery apparatus according to claim 2, wherein said control means comprises a program storage means for correcting myopia.

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