| Apparatus for calculation of ablation data on a cornea for refractive correction and apparatus for operation on a cornea for refractive correction -> Monitor Keywords |
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Apparatus for calculation of ablation data on a cornea for refractive correction and apparatus for operation on a cornea for refractive correctionRelated Patent Categories: Surgery, Instruments, Light Application, SystemsApparatus for calculation of ablation data on a cornea for refractive correction and apparatus for operation on a cornea for refractive correction description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060206104, Apparatus for calculation of ablation data on a cornea for refractive correction and apparatus for operation on a cornea for refractive correction. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention is a continuation of application Ser. No. 09/121,917, filed Jul. 24, 1998, pending. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an apparatus for operation on a cornea, and more particularly to the apparatus which corrects ametropia by ablating a corneal surface with a laser beam, being suitable for correcting simple myopic astigmatism and mixed astigmatism. [0004] 2. Description of Related Art [0005] In conventional art, there is known an apparatus for operation on a cornea, which corrects ametropia of an examined eye by ablating a corneal surface with an excimer laser. Several methods have been proposed for laser irradiation for such a kind of the apparatus, to include a one shot irradiation method which covers an irradiation area of a cornea with only one shot, a scanning slit method which puts side by side with superposing a slit (rectangular) shaped laser beam in a width direction, and a scanning spot method which converges a laser beam to a diameter of 1 to 2 mm, then scans with high velocity by wagging the laser beam with a mirror having two axes of X and Y. The apparatus acting on above mentioned method enables one to perform such operations as to correct myopia and compound myopic astigmatism, further enabling one to correct hyperopia. [0006] A typical method of correcting myopic astigmatism is to flatten the cornea in a strong principal meridian direction. One such method is to ablate the whole cornea in a strong principal meridian direction by enlarging an optical zone, and the other method is to ablate only a central part in a strong principal meridian direction selectively. [0007] However, since a corneal surface is curved, a central part of cornea differs from that of a periphery of cornea in an energy density of a laser irradiation. Accordingly, in case of the method of correcting myopic astigmatism by ablating the whole in a strong principal meridian direction, an ablation of the periphery tends to be slight as a whole, thus resulting in such a problem that a spherical component is shifted to a hyperopic direction. [0008] On the contrary, in the case of the method of correcting myopic astigmatism by ablating only a central part in a strong principal meridian direction selectively, since a small area in a strong principal meridian direction can be ablated, a spherical component is shifted little. However, because of a small optical zone, there is such a problem that a patient's eye is influenced by an optical disorder such a as glare or a halo. [0009] In addition, in the case of correction for mixed astigmatism showing such symptoms as to be myopia on a strong principal meridian and to be hyperopia on a weak principal meridian, a method combines an ablation in a strong principal meridian direction with an ablation for correcting hyperopia. By combining simply, there are such problems that an ablation amount becomes much and a satisfactory result is not obtained. SUMMARY OF THE INVENTION [0010] The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an apparatus for use in operating on a cornea, which can correct astigmatism, such as simple myopic astigmatism and mixed astigmatism, accurately and easily by ablating the whole of an optical zone. [0011] Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. [0012] To achieve the objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, an apparatus for operation on a cornea by ablating with a laser beam for correcting ametropia, the apparatus of this invention comprises input means utilized for inputting each data necessary for correction, first correcting means for irradiating a laser beam for correcting myopic astigmatism, second correcting means for irradiating a laser beam for correcting hyperopic astigmatism, calculating means for calculating each correction-data based on the inputted data in the case of combining the first and second correcting means, and control means for ablating the cornea by controlling the first and second correcting means based on results calculated by the calculating means. [0013] Another aspect of the present invention, an apparatus for operation on a cornea by ablating with a laser beam for correcting ametropia, the apparatus comprises first correcting means for irradiating a laser beam for correcting myopic astigmatism, second correcting means for irradiating a laser beam for correcting hyperopic astigmatism, data input means utilized for inputting each data, such as an amount of astigmatism correction and a direction of a cylindrical axis, which is to be corrected by the first and second means in order to correct simple myopic or mixed astigmatism, and control means for ablating a cornea by controlling the laser irradiation performed by the first and second correcting means based on the inputted data. [0014] Further, another aspect of the present invention, an apparatus for operation on a cornea, comprises irradiation optical system for irradiating a laser beam for surgery onto a patient's cornea, moving means for moving the laser beam to a direction intersecting with an optical axis of the irradiation optical system, rotation means for causing the laser beam to rotate around the optical axis of the irradiation optical system, a circular aperture for restricting a corneal ablation area to be ablated by the laser beam, disposed at the irradiation optical system, a slit aperture for limiting the ablation area limited by the circular aperture to be a slit-shape, the slit aperture being variable, data input means utilized for inputting each data necessary for desiring a corneal shape after the ablation, first irradiating means for irradiating a laser beam by causing a width of the slit aperture to vary toward a strong principal meridian direction for correcting astigmatism, under the condition that the laser beam is rotated by the rotation means every time when the laser beam is scanned by the moving means, second irradiating means for irradiating a laser beam by shifting a position of the laser beam moved by the moving means under the condition that the laser beam is rotated by the rotation means so that a moving direction of the laser beam by the moving means may vary toward a weak principal meridian direction for correcting astigmatism within an area limited by the circular aperture, and control means for calculating each amount of ablation in both strong and weak principal meridian directions based on the data inputted by the data input means, and controlling combination of the first and second irradiating means based on the amount of ablation. [0015] According to the present invention, simple myopic astigmatism and mixed astigmatism can be corrected accurately and easily by utilizing an optical zone at which a patient's eye is not influenced. In addition, in the case of combining an ablation in a strong principal meridian direction with an ablation in a weak principal meridian direction, the apparatus is configured so as to calculate data utilized for converting an astigmatism sign and a rotation of a cylindrical axis, therefore, accurate laser irradiation can be performed with avoiding a possible serious involvement induced by disorder of a cylindrical axis. BRIEF DESCRIPTION OF THE DRAWINGS [0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings, [0017] FIG. 1 is a schematic view showing a corneal part to be ablated in order to correct myopic astigmatism; [0018] FIG. 2 is a schematic view showing a corneal part to be ablated in order to correct hyperopic astigmatism; and [0019] FIG. 3 is a view showing a schematic arrangement of an optical system and a schematic construction of a control system of an apparatus of a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0020] A detailed description of one preferred embodiment of an apparatus for operation on a cornea embodying the present invention will now be given referring to the accompanying drawings. Firstly, a method of correcting myopic astigmatism and mixed astigmatism according to the present invention will be described below. Continue reading about Apparatus for calculation of ablation data on a cornea for refractive correction and apparatus for operation on a cornea for refractive correction... 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