JPH06339464A - Ultrasonic probe for measuring thickness of cornea - Google Patents

Abstract

PURPOSE:To provide a probe for a measuring apparatus capable of measuring the thickness of the cornea and its distribution with accuracy using an ultrasonic beam incident on the cornea in a normal direction by pressing the cornea without causing strain and wrinkles. CONSTITUTION:The contact terminal 3 of a probe 1 has spherical recesses 6 formed at its contact end face 5 and the points of passage of an ultrasonic beam generated a vibrator 4, the contact end face 5 being presses by the cornea C and having grooves formed therein to communicate the recesses 6 with the outside of the contact end face 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe for measuring corneal thickness. More specifically, the present invention relates to an ultrasonic probe for corneal thickness measurement for measuring the thickness of the cornea and its distribution by ultrasonic waves.

[0002]

2. Description of the Related Art In recent years, in the field of ophthalmology, a surgical operation for correcting myopic eyes called radial keratotomy, in which an incision of a predetermined shape and depth is made on the surface of the cornea, is becoming popular as an eye refractive correction operation. Furthermore, recently, surgery is being performed to correct myopia by automatic removal of the corneal surface by excimer laser. At that time, by accurately measuring the corneal thickness and the thickness distribution immediately before the operation, it becomes possible to adjust the knife blade length or the laser irradiation power based on the measurement result.

Conventional corneal thickness measuring devices include an optical type and an ultrasonic type. Since the optical type is non-contact with the cornea, alignment operation such as positioning and focusing of the measuring device with respect to the eyeball to be operated. However, the correction is necessary due to the difference in the curvature of the cornea. On the other hand, the ultrasonic type is a type that makes contact with the cornea, but it is widely used because alignment is easy. What is generally used as an ultrasonic type is a probe to which one ultrasonic transducer is attached.

However, in the case of a probe to which one ultrasonic transducer is attached, the probe is moved over the cornea to measure the thickness of the cornea and its distribution. It is decided only by a guide, and the accuracy of position accuracy is lacking.

Therefore, recently, a probe (multipoint probe) having a plurality of ultrasonic transducers for measuring the thickness distribution of the cornea at one time has been proposed. For example, Japanese Patent Laid-Open No. 62-1067
No. 50 and Japanese Patent Application Laid-Open No. 2-261438.

In the probe disclosed in Japanese Unexamined Patent Publication (Kokai) No. 62-106750, a fixation lamp is arranged at the center of the multipoint probe or symmetrically with the center so that the subject can fix the eye. The center of the cornea and the center of the probe are made to coincide with each other. However, the examiner cannot confirm whether or not the examinee is gazing and the position accuracy is not guaranteed.

Further, the probe disclosed in Japanese Patent Laid-Open No. 2-261438 discloses a contact medium between a contact end surface having a concave spherical surface centered on the focal point of an ultrasonic beam from an ultrasonic transducer and a front surface of the cornea. For example, by interposing a liquid layer such as spicosol, it is possible to easily distinguish the echo on the contact end surface from the echo on the anterior surface of the cornea, and increase the accuracy of the measured value of corneal thickness.

[0008]

However, in the above-mentioned conventional probe (JP-A-2-261438), no matter how the contact end face is formed into a curved surface having the same curvature as the cornea, They cannot be the same, and a slight difference in curvature always occurs. Moreover, it is even more difficult to use it for many eyeballs.

As a result, it is difficult to irradiate the front surface of the cornea with the ultrasonic beam in the direction of its normal line, which makes it difficult to accurately measure the film thickness.

On the other hand, even if the curvatures of the contact end surface and the cornea do not completely match (substantially match), it is possible to match the curvatures of both by pressing the contact end surface against the front surface of the cornea. Is. However, this is because the front surface of the eyeball is bent and matched, and therefore the problem that wrinkles and distortions occur on the corneal surface and the measured value of corneal thickness is still inaccurate cannot be solved.

The present invention has been made to solve such a problem, and it is possible to perform accurate alignment by pressing the contact terminal without generating wrinkles or strains that hinder the thickness measurement on the corneal surface. The purpose is to provide an ultrasonic probe for measuring corneal thickness (hereinafter, simply referred to as a probe).

[0012]

The probe of the present invention irradiates an ultrasonic beam in a contact terminal whose contact end face with the cornea has a curvature substantially the same as that of the corneal surface and an ultrasonic beam in the normal direction of the contact end face. An ultrasonic probe for corneal thickness measurement having a plurality of ultrasonic transducers arranged so that each of the portions corresponding to the ultrasonic beam irradiation position on the contact end face of the contact terminal It is characterized in that a recess is formed.

It is preferable that a groove is formed on the contact end surface of the contact terminal, the groove connecting the recess and the peripheral edge of the contact end surface.

[0014]

According to the probe of the present invention, when the contact end face is pressed against the cornea, each recess is filled with a liquid such as tears, scopisol, or an anesthetic, so that the ultrasonic beam is just incident. Since no compressive force is applied to the portion of the cornea corresponding to the region (recess), harmful wrinkles and flexure are less likely to occur. Therefore, the curvature of the corneal surface can be matched with the curvature of the contact end surface without any obstacle. Moreover,
Due to the presence of the recess, there is a distance between the corneal surface and the surface of the contact terminal (so to speak, the bottom of the recess) at the site where the ultrasonic beam is incident. Will also be easier.

Therefore, in the probe of the present invention, the ultrasonic beam can be incident on the anterior surface of the cornea in the normal direction, and the accuracy of the measured value of corneal thickness is improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a probe of the present invention will be described with reference to the attached drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the probe of the present invention, FIG. 2 is an enlarged sectional view of an essential part of the probe of FIG. 1 in use, and FIG. 3 is a probe of FIG. FIG.

In FIG. 1, reference numeral 1 is a probe in which a housing 2 is provided with a contact terminal 3 and a plurality of ultrasonic transducers (hereinafter, simply referred to as transducers) 4. C is the cornea of the eye to be inspected. In this embodiment, the plurality of vibrators 4 are arranged on the rear end surface of the contact terminal 3 in a radial and spherical shape from the center thereof.

The tip end surface of the contact terminal 3, that is, the contact end surface 5 for contacting the cornea C has a concave spherical surface having substantially the same curvature as the surface of the cornea C (having a spherical surface).
(Usually, the radius of curvature is in the range of 7 to 9 mm) A plurality of recesses 6 having a depth of 0.2 mm or more are formed. Each of the recesses 6 is formed in a portion irradiated with an ultrasonic beam emitted from each of the plurality of transducers 4. That is, they are arranged radially as shown in FIG.

The contact terminal 3 is an acoustic medium and is made of a material having excellent ultrasonic characteristics such as PMMA or polydimethylpentene.

When measuring the corneal thickness using a probe formed as described above, a corneal protective agent such as scopisol or a liquid such as an anesthetic is applied to the contact end surface, and then the cornea C to be inspected. The contact end surface 5 and the cornea C are made to conform to each other by pressing the surface of the cornea C. Then, all the transducers 4 are driven to measure the thickness of each part of the cornea C at one time.

As shown in FIGS. 2 (a) and 2 (b),
The ultrasonic beam from the oscillator 4 produces echoes at the bottom 6a of the recess 6, the front surface Ca of the cornea C, and the rear surface Cb of the cornea C,
Since the depth of the recess 6 is 0.2 mm or more as described above, the bottom 6a of the recess 6 and the front surface C of the cornea C
It becomes easy to distinguish the echoes in a. That is,
The anterior position of the cornea C becomes clear, and the accurate corneal thickness can be measured. Conventionally, scopisol or the like is interposed between the contact end surface and the front surface of the cornea, so that a narrow gap is generated, and it is difficult to distinguish echoes. In addition, in the graph of FIG.
The horizontal axis shows the distance converted from the time difference, and the vertical axis shows the echo intensity.

Further, when the contact terminal 3 is pressed against the cornea C, the pressing on the measuring point of the cornea C, that is, the portion corresponding to the recess 6 is released by the recess 6, so that the occurrence of strain is prevented. It As a result, the ultrasonic beam is incident on the cornea C in the direction normal to the surface thereof, so that the accurate thickness can be measured.

The shape of the recess 6 is not particularly limited, but it has a spherical surface in order to improve the measurement sensitivity and the measurement accuracy due to the acoustic lens effect occurring in the recess 6 and the convergence of the ultrasonic beam. Is preferred. Furthermore, the ultrasonic beam is focused between the anterior surface and the posterior surface of the cornea C (in the cornea) at the point that the intensity of the echo on the anterior surface and the posterior surface of the cornea C becomes similar and the measured value becomes more accurate. It is more preferable to determine the curvature of the inner surface of the recess 6.

FIG. 3 shows the contact end surface 5 of the probe of this embodiment. The plurality of recesses 6 arranged radially are
Each is communicated with the outside by a groove 7 extending to the peripheral edge of the contact end surface 5. The groove 7 improves the flow of liquid such as scopisol and prevents adsorption of the both 5 and C when the contact end surface 5 is pressed against the cornea C. Moreover, there is an effect that the pressure on the cornea C can be further reduced. Further, even when bubbles are carelessly mixed in the liquid such as scopisol, it can be easily removed from the groove 7, so that the scattering of ultrasonic waves is prevented.

In the present invention, the number of ultrasonic transducers and the number of recesses are not limited to the above 13, but may be increased or decreased as necessary. Further, the arrangement of the ultrasonic transducers and the recesses is not particularly limited to the radial shape, and may be, for example, a concentric shape or a base-like shape.

[0027]

EFFECTS OF THE INVENTION The probe of the present invention has a recess formed on the contact end surface thereof, so that the adverse effect of the liquid layer on the measured value of corneal thickness is prevented and wrinkles and distortion of the cornea are prevented. It is also possible to prevent corrosiveness and to make an accurate measurement of the corneal thickness by making the ultrasonic beam incident on the cornea in the normal direction.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a probe of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the probe of FIG. 1 when used.

3 is a front view of the probe shown in FIG. 1. FIG.

[Explanation of symbols]

 1 Probe 3 Contact Terminal 4 Ultrasonic Transducer 5 Contact End Face 6 Recess 7 Groove C Cornea

Claims (2)

[Claims] 1. A contact terminal whose contact end face with the cornea has a curvature substantially the same as that of the corneal surface, and a plurality of ultrasonic waves arranged so as to irradiate an ultrasonic beam in a direction normal to the contact end face. An ultrasonic probe for measuring corneal thickness having a vibrator, characterized in that a recess is formed in each portion corresponding to an ultrasonic beam irradiation position on a contact end face of the contact terminal. Ultrasonic probe for measuring corneal thickness. 2. The ultrasonic probe for measuring corneal thickness according to claim 1, wherein a groove is formed on the contact end surface of the contact terminal, the groove communicating the recess with the peripheral edge of the contact end surface.