JPH09266925A - Ablation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ablation apparatus capable of efficiently cutting only protruding parts of an uneven surface in a short time, by equipping a beam moving means, a division mask means, a data inputting means, and a control means for the masking state of the division mask means at each moving position of a laser beam by a moving means based on the inputted data. SOLUTION: A laser beam projected from a laser light source 1 is formed into a desired rectangular shape by a beam forming means such as an expander lens if necessary. Parts to be shielded by the division mask 3 to divide the laser beam in the horizontal direction and to shield them partially are selectively changed by a division mask drive device 4. An image rotator 7 is driven to be rotated around the optical axis L by an image rotator drive device 8 to rotate the laser beam around the optical axis. A control device 22 to control the total apparatus controls the laser light source 1, division mask drive device 4, a mirror drive device 6, the image rotator drive device 8, an aperture drive device 10, and a division mask moving device 15, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ablation device for ablating the surface of an object, and more particularly to an ablation device suitable for correcting irregularities on the corneal surface by selectively excising only the convex portion of the cornea such as irregular astigmatism. .

[0002]

2. Description of the Related Art In recent years, a PRK (Photorefractive K) that ablates the surface of the cornea with a laser beam and changes its curvature to correct the refractive error of the eyeball.
eratectomy) and laser beam ablation to remove lesions on the corneal surface PTK (Phototheraputic)
Keratectomy) is attracting attention. This PRK, PTK
The ablation of the laser beam for performing the above is mainly performed by the following three methods.

The first is a method of ablating a predetermined area at a time with a large area laser beam, and the second is a method of moving a rectangular laser beam to ablate a predetermined area. The third is a method of ablating a predetermined area by scanning a small spot two-dimensionally.

[0004]

However, the cornea of the human eye is not always a spherical surface or a toric surface, but the corneal surface may be partially uneven due to irregular astigmatism or the like. When such a corneal surface is ablated with a laser beam to form a spherical surface or a toric surface, a first large area beam method or a second rectangular beam method is moved. However, there is a drawback that it takes much time to cut the convex portions one by one by aligning the irradiation areas for the respective convex portions.

On the other hand, in the method of scanning the third small spot, it is sufficient to selectively scan only the convex portion for ablation, and the excision can be performed in a shorter time than in the first and second methods. Even so, if there are many convex portions to be abraded, there is a drawback that it takes a relatively long time.

The present invention has been made in view of the above problems of the prior art.
It is a technical object to provide an ablation device that can efficiently excise only the convex portion of the uneven surface in a short time.

Further, it is a technical object to provide an ablation device capable of smoothly removing a convex portion on the surface.

[0008]

The present invention is characterized by having the following configuration in order to solve the above-mentioned problems.

(1) A light guide optical system for guiding a slender rectangular laser beam to an ablation object is provided, and the convex portion of the object having an uneven surface is provided by the guided laser beam. In the ablation device for ablating the laser beam, a beam moving means for moving the laser beam with respect to the optical axis of the light guiding optical system and a longitudinal direction of the laser beam are selectively divided. Division masking means for masking, a data inputting means for inputting data relating to the ablation area of the object, and each movement of the laser beam by the moving means based on the input data. Control means for controlling a mask state of the divided mask means at a position.

(2) The divided mask means of (1) is characterized by having a large number of strip-shaped masks arranged side by side.

(3) The divided mask means of (2) is characterized in that it has rotary opening / closing means for rotating / opening / closing each of the strip masks.

(4) The divided mask means of (2) has a slide opening / closing means for sliding and opening / closing the strip masks.

(5) A light guide optical system for guiding a rectangular laser beam having a slender rectangular cross section in a plane perpendicular to the optical axis to the ablation target is provided, and the guided laser beam has an uneven surface. In an ablation device for ablating a convex portion, a beam moving means for moving a laser beam in a direction orthogonal to the optical axis of the light guiding optical system, and a division mask for selectively dividing and masking the longitudinal direction of the laser beam. Means, divided mask moving means for moving the divided mask means in the longitudinal direction of the laser beam, data input means for inputting data on the ablation region of the object, and laser beam by the beam moving means based on the input data. The mask state of the divided mask means and the moving position of the divided mask moving means at each moving position of And a control unit for controlling.

(6) In the ablation device of (5), the divided mask means is a strip-shaped mask arranged in parallel in the longitudinal direction of the laser beam having a rectangular cross section.
Mask insertion / removal means for partially blocking the longitudinal direction of the rectangular laser beam by selectively inserting / removing the strip-shaped mask into / from the light guide optical system.

(7) In the ablation device of (5), the strip mask and the mask inserting / removing means according to claim 6 are provided, and each of the strip masks has substantially the same width in the longitudinal direction of the laser beam. The division mask moving means can move the whole division mask in the longitudinal direction of the laser beam, and the control means moves the division mask so that the whole division mask moves by a movement amount which is apparently smaller than the width of the mask. It is characterized by controlling.

(8) In the ablation apparatus of (5), the control means controls the mask moving position by the divided mask moving means with respect to the ablation object in units of one scan of the laser beam. .

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic arrangement of an optical system and a schematic configuration of a control system of the apparatus of the embodiment.

Reference numeral 1 denotes a laser light source, which is 193 in the embodiment.
An excimer laser with a wavelength of nm is used. The excimer laser beam emitted from the laser light source 1 is a pulse wave, and its typical shape is, as shown in FIG. 2, the intensity distribution of the beam F (W) which is almost uniform in the horizontal direction (X-axis direction). And has a Gaussian distribution F (H) in the vertical direction (Y-axis direction). In addition, the cross-sectional shape on a plane perpendicular to the optical axis is an elongated rectangular shape.

The laser beam emitted from the laser light source 1 is shaped into a desired rectangular shape by a beam shaping means such as an expander lens if necessary. A plane mirror 2 deflects the laser beam emitted from the laser light source 1 in the horizontal direction upward by 90 °.

3 is the horizontal direction of the laser beam (X-axis direction)
Is a divided mask for dividing and partially shielding, and the portion to be shielded is selectively changed by the divided mask driving device 4. When the split mask 3 is viewed from the laser light source 1 side, as shown in FIG. 3A, a large number of strip-shaped masks having substantially the same width are arranged side by side, and the strip-shaped masks are opened and closed respectively. By doing so, the longitudinal direction of the elongated rectangular laser beam can be partially cut. As for opening and closing of each strip-shaped mask, as shown in FIG. 3B, each strip-shaped mask is rotated by the rotating mechanism to selectively change the portion to be shielded. That is, the laser beam passing through the divided mask 3 has a shape in which the closed mask is partially cut by selectively opening and closing the strip masks. The strip-shaped mask may be opened and closed by rotation, or may be slid in the vertical direction of the laser beam as shown in FIG.

Further, the divided mask 3 is moved by the divided mask moving device 15 in the longitudinal direction of the laser beam (X-axis direction). The movement range secures at least the width of one strip-shaped mask, and the entire divided mask 3 can move a minute distance within the width of one mask.

The laser beam that has passed through the split mask 3 is
It is deflected in the horizontal direction by the plane mirror 5. The plane mirror 5 is movable in the vertical direction (arrow direction) by the mirror driving device 6, and the laser beam is moved in parallel in the Gaussian distribution direction to uniformly ablate the object. This point is described in detail in Japanese Patent Application Laid-Open No. 4-242644 (Invention title “Ablation device by laser beam”).
This is incorporated.

Reference numeral 7 denotes an image rotator, which is rotationally driven by the image rotator driving device 8 about the optical axis L to rotate the laser beam around the optical axis. Reference numeral 9 is a variable circular aperture that limits the ablation region, and the aperture region of the aperture 9 is the aperture driving device 10.
Can be changed by Reference numeral 11 is a projection lens for projecting the aperture 9 onto the cornea 13 of the patient's eye. The aperture 9 and the cornea 13 have a conjugate positional relationship with the projection lens 11, and the area defined by the aperture 9 is the cornea 1
Image on 3 to limit the ablation area.

Reference numeral 12 is a dichroic mirror having a characteristic of reflecting an 193 nm excimer laser beam and transmitting visible light. The laser beam passing through the projection lens 11 is bent by 90 ° by the dichroic mirror 12 to form a cornea 13 of the patient's eye. Is guided to.

The patient's eye is prepositioned so as to come to a predetermined position during the operation (the description of the positioning means is omitted because it has little relation to the present invention).

An observation optical system 14 having a binocular surgical microscope is located above the dichroic mirror 12.
As the binocular observation optical system, a commercially available one can be used, and the configuration itself is not related to the present invention, so that the description is omitted.

Reference numeral 20 denotes a control device for controlling the entire apparatus, which controls the laser light source 1, the divided mask driving device 4, the mirror driving device 6, the image rotator driving device 8, the aperture driving device 10 and the divided mask moving device 15. . Reference numeral 21 is a data input device for inputting corneal shape data and the like of the patient's eye.

The operation of the apparatus having the above configuration will be described.

First, the refraction correction by the laser beam will be briefly described. The cornea of the patient's eye is fixed in position with respect to the device. The ablation region and its shape are determined according to a program stored in the control device 20 based on the data such as the refracting power input in advance by the data input device 21, thereby controlling the operation of the device. When refraction is corrected, all the masks of the divided mask 3 are opened.

In the case of myopia correction, the laser beam is limited by the aperture 9 and the plane mirror 5 is sequentially moved to move the laser beam in the Gaussian distribution direction. Then, each time the laser beam moves from one end to the other and finishes moving on one surface (one scan), the moving direction of the laser beam is rotated by the image rotator 7 to cut the laser beam into a uniform circle. By sequentially changing the size of the aperture 9, the central part of the cornea is ablated deeply and the peripheral part is ablated shallowly. This corrects myopia.

In the case of hyperopia correction, first, the opening region of the aperture 9 is fixed to limit the ablation region. The plane mirror 5 is displaced with respect to the optical axis L to shift the laser beam, and the image rotator 7 is rotated to repeat ablation, thereby ablating the cornea annularly. Then, as the displacement of the laser beam from the optical axis L is increased by sequentially moving the plane mirror 5, the number of irradiation pulses (irradiation time) is increased, so that the central portion becomes shallower and the peripheral portion can be deeply ablated. Correction is performed. The frequency control is performed by changing the total irradiation pulse number without changing the ratio of the irradiation pulse number (irradiation time) at each position of the laser beam deviated from the optical axis L by the movement of the plane mirror 5. . Details of this correction of hyperopia are described in Japanese Patent Application No. 6-166231 (the name of the invention "corneal surgery device") filed by the present applicant.

Next, the operation of selectively cutting off only the convex portion of the cornea such as irregular astigmatism will be described with reference to the flowchart of FIG.

Now, it is assumed that the cornea 13 having the convex portion of the shaded portion as shown in FIG. 5 is ablated to remove the convex portion to form a spherical surface. The X axis and the Y axis in the figure show the distribution direction of the laser beam.

First, the data of the surface shape of the cornea 13 to be ablated is input by the data input device 21. The control device 20 calculates the ablation amount at each position on the corneal surface based on the surface shape data, and controls the moving position of the plane mirror 5 and the opening / closing and moving amount of the strip mask of the split mask 3 to perform the ablation. . The mirror 5 is moved in synchronization with the laser pulse,
In the following description, the mirror 5 is moved for each shot for convenience. In this embodiment, the image rotator 7
The ablation is performed in a fixed state, but the image rotator 7 can be rotated and controlled for each scan if necessary.

In the first one scan, the divided mask 3 is placed at the initial position (coordinates are x = x ₁ ) and laser irradiation is performed. At the time of the first shot, the plane mirror 5 is located at the extreme end. The projection position of the laser beam at the position of the plane mirror 5 comes to the end of the cornea 13 as shown by the dotted line in FIG. However, since there is no convex portion to be removed at this position, the control device 20 closes all the strip masks of the divided mask 3. The laser beam emitted from the laser light source 1 is completely cut by the split mask 3, and the cornea 13 is not ablated.

In the second shot, the controller 20 moves the plane mirror 5 by a fixed amount in synchronization with the laser pulse. The projection position of the laser beam at this position comes to the position shown in FIG. 6B, but since there is no convex portion to be removed at this time as well, all the division masks 3 are kept closed. The laser beam is all cut, and again the cornea 13 is not ablated.

In the third shot, the plane mirror 5 also moves a fixed amount. The projection position of the laser beam comes to the position indicated by the dotted line in FIG. Since there is a convex portion to be removed at this position, the control device 20 controls the operation of the divided mask driving device 4 based on the shape information of the convex portion, and selectively selects the strip-shaped mask portion of the divided mask 3 corresponding to the convex portion. Open to. The cornea 13 is irradiated with the laser beam that has passed through the opened mask portion, and the convex portion of the shaded portion in the figure is ablated.

On the fourth shot, the projection position of the laser beam is changed to the dotted line position in FIG. 6 (d) by the movement of the plane mirror 5, the mask portion of the divided mask 3 corresponding to the convex portion is opened, and the diagonal line of the cornea 13 is opened. The part is ablated. Fifth
Similarly for the shot eye, the movement of the plane mirror 5 and the opening and closing of the mask portion of the divided mask 3 corresponding to the convex portion ablate the cornea in the shaded portion of FIG. 6 (e).

Continuing this, FIG. 6 (f) for the nth shot
After that, the plane mirror 5 moves to the opposite end,
Scan ablation is complete.

Subsequently, the control device 20 moves the divided mask 3 by Δx in the laser beam longitudinal direction (X-axis direction) via the divided mask moving device 15. FIG. 7A shows the ablation state of the first scan, and FIG. 7B shows the ablation state.
It is explanatory drawing which shows the ablation state of the 2nd scan in the same position on (a) and a cornea.

The control device 20 moves the divided mask 3 to the irradiation position moved by Δx from the first scan via the divided mask moving device 15, and then again based on the input data from the data input device 21 in the same manner as described above. Based on the obtained ablation amount at each position, movement of the plane mirror 5,
Ablation is performed while opening / closing the split mask 3 and controlling the number of laser irradiation pulses (irradiation time).

The plane mirror 5 is controlled to move from the end position of the first scan to the start position in the direction opposite to the moving direction of the first scan. Specifically, after the ablation of the first scan is performed from the upper side to the lower side of the cornea in FIG. 5, the ablation of the second scan is performed from the lower side to the upper side. This is repeated from the third scan onward.

The divided mask 3 is moved in the X direction by Δx after the third scan and is repeated until it is moved to the final position (coordinate x = x _fin ). The movement amount Δx for each scan does not have to be constant, and the opening / closing of the divided mask 3 and the laser irradiation pulse number (irradiation time) at each irradiation position based on the movement amount Δx may be controlled.

Thus, based on the information on the shape of the convex portion of the cornea 13, ablation is performed while controlling the movement of the laser beam by the plane mirror 5 and the opening and closing of each strip mask of the split mask 3, and the height of the convex portion is further increased. By repeating the process until the convex portion is excised based on the depth information, the convex portion in the hatched portion in FIG. 5 is removed and the cornea 13 becomes spherical.

Further, by finely moving the divided mask 3 in the longitudinal direction of the laser beam, the coordinates of the spot by the selectively opened mask increase, and the ablation areas of the respective scans can be overlapped. As a result, it is possible to smooth the ablation surface by eliminating the step at the divided portion of each mask.

The ablation depth at each position is
Since it is determined by the relationship between the intensity of the laser beam per pulse and the number of pulses to be irradiated, this relationship determines the opening and closing of each strip mask and the moving amount of the divided mask at each moving position of the laser beam.

In the present embodiment, the laser beam was reciprocally moved on the cornea for ablation control.
The ablation of the scan can be performed in the same movement direction as the first scan (from the upper side to the lower side of the cornea in FIG. 5). In this case, the plane mirror 5 is set after each scan.
To the initial position, or set the image rotator 7 to 1.
It is rotated by 80 ° and only the laser beam is in the initial position (Fig.
After moving to the same position as the position (a), the plane mirror 5 is controlled to move.

The present invention is not limited to the shape of the divided masks described in the embodiments, but various modifications are possible, and the invention is included in the scope of the same technical idea.

[0049]

As described above, according to the present invention,
It is possible to efficiently ablate a convex portion of an object having an uneven surface in a short time.

Also, the surface to be ablated can be smoothed.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic arrangement of an optical system and a schematic configuration of a control system of an apparatus according to an embodiment.

FIG. 2 is a diagram showing a typical shape of an excimer laser beam.

FIG. 3 is a diagram illustrating a shape of a split mask and an opening / closing mechanism.

FIG. 4 is a diagram illustrating another opening / closing mechanism of the split mask.

FIG. 5 is a diagram showing a cornea having a convex portion, for explaining the operation of selectively excising only the convex portion of the cornea.

FIG. 6 is a diagram illustrating an ablation process of the convex portion of the cornea shown in FIG.

FIG. 7 is a diagram illustrating a change in an ablation region due to movement of a division mask.

FIG. 8 is a flowchart illustrating an operation of selectively removing only a convex portion of the cornea such as irregular astigmatism.

[Explanation of reference numerals] 1 laser light source 3 divided mask 4 divided mask driving device 5 plane mirror 6 mirror driving device 13 cornea 15 divided mask moving device 20 control device 21 data input device

Claims (8)

[Claims] 1. A light-guiding optical system for guiding a slender rectangular laser beam to an ablation target object, wherein a convex portion of an object having an uneven surface is formed by the guided light beam. In an ablation device for ablation, a beam moving means for moving a laser beam with respect to the optical axis of the light guide optical system and a longitudinal direction of the laser beam are selectively divided. Dividing mask means for masking by means of data, data input means for inputting data relating to the abrasion area of the object,
A control means for controlling the mask state of the divided mask means at each moving position of the laser beam by the moving means based on the input data.
Device. 2. The ablation device according to claim 1, wherein the divided mask means has a large number of strip-shaped masks arranged side by side. 3. The ablation apparatus according to claim 2, wherein the divided mask means has a rotating opening / closing means for rotating / opening / closing each of the strip masks. 4. The ablation apparatus according to claim 2, wherein the split mask means has slide opening / closing means for sliding and opening / closing the strip masks. 5. A light guide optical system for guiding a rectangular laser beam having a slender rectangular cross section in a plane perpendicular to the optical axis to an ablation target, the convex part of the target having an uneven surface by the guided laser beam. In an ablation device for ablating a portion, a beam moving means for moving a laser beam in a direction orthogonal to the optical axis of the light guiding optical system, and a dividing mask means for selectively dividing and masking the longitudinal direction of the laser beam. And divided mask moving means for moving the divided mask means in the longitudinal direction of the laser beam,
Data input means for inputting data relating to the ablation region of the object, mask state of the divided mask means and movement position of the divided mask movement means at each movement position of the laser beam by the beam movement means based on the input data And a control means for controlling the ablation device. 6. The ablation device according to claim 5, wherein the split mask means has a plurality of strip-shaped masks arranged in parallel in a longitudinal direction of a laser beam having a rectangular cross-section, and the strip-shaped masks are used to guide the light. An ablation device comprising: a mask insertion / removal means for partially blocking the longitudinal direction of the rectangular laser beam by selectively inserting / removing the optical system. 7. The ablation device according to claim 5, comprising the strip-shaped mask according to claim 6 and a mask inserting / removing means, each strip-shaped mask having substantially the same width in the longitudinal direction of the laser beam, The divided mask moving means can move the entire divided mask in the longitudinal direction of the laser beam, and the control means moves the divided mask moving means so that the entire divided mask moves with a movement amount that is apparently smaller than the width of the mask. An ablation device that is controlled. 8. The ablation apparatus according to claim 5, wherein the control means controls a mask moving position by the divided mask moving means with respect to the ablation object in units of one scan of a laser beam. apparatus.