Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
2002-01-24
2003-09-02
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
Reexamination Certificate
active
06612698
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of Japanese Patent Application No. 2001-017477, filed on Jan. 25, 2001, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pupil measurement apparatus, refraction correction apparatus, and pupil measurement method and, more particularly, to a visual function correction apparatus which irradiates a cornea with a laser beam to correct the corneal shape and correct refraction.
2. Description of the Related Art
Conventionally, refraction correction surgeries such as LASIK (LAser in SItu Keratomileusis) are used to correct refraction, in which a cornea is irradiated with an excimer laser to change the corneal shape (e.g., the radius of curvature or distortion), i.e., to change the refracting power of the cornea, thereby correcting the refraction. In LASIK, the surface of the cornea of an eyeball is stripped off thin by an electric knife. Then, the cornea is shaved by irradiating it with an excimer laser. Finally, the stripped corneal surface is returned to the original position, thereby correcting the corneal shape for refraction correction.
For example, near-sightedness occurs because the radius of curvature of a cornea is small, and an image is formed before a retina. To correct the near-sightedness, the cornea is uniformly shaved to increase its radius of curvature, i.e., to make the cornea flatter to correct the visual acuity. Hence, to correct near-sightedness, the cornea is irradiated with a laser beam such that a round laser beam irradiation region is formed.
Additionally, for example, astigmatism occurs because the corneal shape is nonuniform and distorted due to, e.g., the index distribution depending on the elliptical direction of the corneal lens of an eye. To correct the astigmatism, the cornea is shaved to change the radius of curvature at each position of it, thereby correcting the visual acuity.
Hence, to correct near-sightedness including astigmatism when a cornea has, e.g., an elliptical distortion, the cornea is irradiated with a laser beam such that the laser beam irradiation region has an elliptical shape having a major axis perpendicular to the major axis of the elliptical distortion to make the corneal shape uniform.
FIG. 16
is a block diagram showing the arrangement of a conventional refraction correction apparatus which irradiates a cornea with a laser beam to change the corneal shape for visual acuity correction.
Referring to
FIG. 16
, a cornea
1604
of an eyeball
1603
is irradiated, through a half mirror
1602
, with light emitted from an imaging light source
1601
. The irradiation light is reflected by the cornea
1604
and supplied to a microscope
1605
and video imaging device
1606
through the half mirror
1602
.
The cornea
1604
is enlarged and observed with the microscope
1605
. Simultaneously, the image of the cornea
1604
is obtained by the video imaging device
1606
, and the obtained image of the cornea
1604
is displayed on a monitor display device
1607
.
For, e.g., near-sightedness correction surgery, the operator strips off a thin surface of the cornea
1604
of the patient using an electric knife. Then, the operator observes marks formed on the eyeball (iris) of the patient in advance with the microscope
1605
and aligns the position of the cornea
1604
with the laser beam irradiation position. When alignment between the position of the cornea
1604
and the laser beam irradiation position is ended, the cornea
1604
is irradiated with a laser beam from a laser irradiation device
1608
through the half mirror
1602
to shave the cornea, thereby correcting refraction.
However, when refraction correction surgery is done using the above-described conventional refraction correction apparatus, marks must be formed on the eyeball (conjunctival portion) of the patient, and the position of the cornea
1604
and the laser beam irradiation position must be aligned while checking the marks with the microscope
1605
. Hence, the operator requires a skill.
Especially, to correct near-sightedness including astigmatism, the cornea
1604
is irradiated with a laser beam with an elliptical irradiation region in refraction correction surgery. Unless the position of the cornea
1604
and the position of the laser beam are accurately aligned in the direction of rotational axis, the cornea
1604
is not correctly irradiated with the laser beam, and the astigmatism cannot be accurately corrected.
Furthermore, since the eyeball of the patient does not stand still during refraction correction surgery, the laser beam irradiation position and the position of the cornea
1604
shift in the directions of X- and Y-axes and rotational axis. Hence, accurate refraction correction surgery is impossible.
The above problems will be described below with reference to
FIGS. 17A
,
17
B,
18
A, and
18
B.
FIGS. 17A and 17B
are views for explaining the position of the cornea
1604
and a laser beam irradiation position
1701
in refraction correction surgery for correcting near-sightedness. When the position of the cornea
1604
and the laser beam irradiation position
1701
are correctly aligned, the center of the laser beam irradiation position
1701
matches the center of the cornea
1604
, as shown in FIG.
17
A. Hence, a desired portion of the cornea
1604
can be shaved to accurately correct near-sightedness.
On the other hand, if the position of the cornea
1604
and the laser beam irradiation position
1701
are not correctly aligned, the center of the laser beam irradiation position
1701
shifts from the center of the cornea
1604
, as shown in FIG.
17
B. Hence, a desired portion of the cornea
1604
cannot be shaved, and consequently, near-sightedness cannot be accurately corrected.
FIGS. 18A and 18B
are views for explaining the position of the cornea
1604
and a laser beam irradiation position
1801
in refraction correction surgery for correcting near-sightedness including astigmatism. When the position of the cornea
1604
and the laser beam irradiation position
1801
are correctly aligned, a desired position of the cornea
1604
can be irradiated with the laser beam, as shown in FIG.
18
A. Hence, the astigmatism can be accurately corrected.
On the other hand, if the position of the cornea
1604
and the laser beam irradiation position
1801
are not correctly aligned, a desired position of the cornea
1604
cannot be irradiated with the laser beam, as shown in FIG.
18
B. Hence, the astigmatism cannot be accurately corrected. Especially, in the refraction correction surgery for correcting near-sightedness including astigmatism, as shown in
FIG. 18B
, if the major axis of the ellipse to be irradiated with the laser beam does not match the major axis of the elliptical laser beam irradiation region due to the torsion of the eyeball, the astigmatism cannot be accurately corrected, though the position of the cornea
1604
matches the central position of the laser beam irradiation position
1801
.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and has as its object to make it possible to accurately measure the position and torsion angle of a cornea without forming any mark on an eyeball to measure the position of the cornea.
It is another object of the present invention to provide a refraction correction apparatus capable of easily and accurately aligning the position of a cornea and a laser beam irradiation position without forming any mark on an eyeball of a patient to align the position of the cornea and the laser beam irradiation position.
According to an aspect of the present invention, there is provided a pupil measurement apparatus comprising an imaging unit for obtaining an image of an eyeball, an arithmetic processing unit for calculating a position and torsion angle of a pupil in the eyeball on the basis of the eyeball image obtained by the imaging unit, and an indicating unit for indicating pieces of information rela
Eguchi Shuichiro
Ise Yasuko
Saito Seiji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Explorer Inc.
Manuel George
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