JPS6331213B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ophthalmological measuring device, and more particularly to a corneal shape measuring device.

A keratometer that measures the shape of the cornea is generally used to measure the three elements of corneal curvature, degree of astigmatism, and astigmatic axis direction, but it is also used to inspect the base curve of contact lenses.

With conventional keratometers, the shape of the corneal reflection image of a ring-shaped chart was observed and measured with the naked eye, so in order to obtain satisfactory accuracy, the magnification was set high to enlarge the corneal reflection image.

As a result, the range that can be observed during alignment and measurement is only a small portion of the cornea, making it extremely difficult to grasp which region of the entire cornea is actually being measured.

In addition, with some types, the anterior segment of the eye could be observed by switching the optical path, but the eye to be examined could not be observed during measurement because the optical path had to be returned and the measurement performed again. . By the way, JP-A-57-139636 discloses a corneal shape measuring device equipped with an observation system for observing the anterior segment of the eye.
It is difficult to observe the shape of the cornea on the observation surface for observing the anterior segment of the eye, and furthermore, it is also impossible to observe only the shape of the cornea in the peripheral region of the anterior segment image. In Japanese Patent Application Laid-Open No. 57-139636, all the optical systems are held integrally and rotated around the objective optical axis, so the position for observing the anterior segment of the eye cannot be fixed.

In view of the above points, the present invention enables positioning without reducing measurement accuracy, allows the anterior eye segment and corneal shape to be observed on the same observation surface regardless of the measurement, and only the corneal shape is observed in the peripheral area of the anterior eye segment image. The purpose of the present invention is to provide a corneal shape measurement device that allows observation.

Examples of the present invention will be described below.

Reference numeral 1 denotes a toric light source, and light emitted from the light source 1 is emitted by a toric cylindrical lens 2 in parallel on each plane including the optical axis l.

The toric cylindrical lens 2 has a surface facing the cornea with a predetermined radius of curvature in each plane including the optical axis l, and has a toric slit 2' at a position separated by the focal length thereof. The light emitted from the slit 2' is emitted in parallel within each plane including the optical axis l, and illuminates the cornea Ec of the eye to be examined.

The light reflected by the cornea Ec diverges and appears to be emitted from the corneal reflection image position Ei. This corneal reflection image
Ei passes through the objective lens 3 and the light splitting mirror 4.

In FIG. 1, the light beam reflected by the light splitting mirror 4 forms an image of the corneal reflection and the surrounding anterior segment on the imaging tube 6 by the imaging lens 5.

The imaging lens 5 is a lens that forms an image of the corneal reflection image and the anterior segment of the eye at a magnification that matches the size of the imaging tube. Using this lens, the magnification of the observation optical system is set to be smaller than the magnification of the measurement optical system. Note that a variable focus lens with variable magnification can be used as the imaging lens 5, and the observation field of view can be adjusted appropriately using, for example, a zoom lens.

The measurement optical system and the observation optical system share the objective lens 3, and the optical paths after the light splitting mirror 4 are independent, so the optical constants such as the magnification and FNo. of each optical system should be selected as necessary. Can be done.

The optical path passing through the light splitting mirror 4 is used for measurement, and the light beam passing through the image rotator 11 is reflected by the mirror 10, deflected by the deflection prism 12, reflected by the mirror 13, the reflection prism 14, and then sent to the image pickup tube 6.
It reaches the top and forms a corneal reflection image. The corneal shape measurement principle of this manual keratometer is widely known, for example, from pages 141 to 143 of "Medical Optical Instruments" edited by Masashi Shimoshima. , a deflection prism that forms a corneal reflection image that is not deflected and a corneal reflection image that is deflected by the deflection prism 12 on the observation surface until the two corneal reflection images are circumscribed in one meridian direction among the two orthogonal meridian directions. The radius of corneal curvature is calculated from the amount of movement in the optical axis direction of 12 (the larger the radius of corneal curvature, the larger the diameter of the corneal reflected image is
Deflection prism 1 until two corneal reflection images are circumscribed
2, the amount of movement in the optical axis direction is small). This also applies to orthogonal meridian directions. That is, the deflection prism 12 is movable in the optical axis direction, and the radius of corneal curvature is measured from the amount of movement until the divided images match.

The image rotator 11 is rotatable in synchronization with the deflection prism 12, thereby making it possible to measure the astigmatism angle. In this case, since the image rotator 11 is located on the opposite side of the optical path from the subject's eye with respect to the light splitting mirror 4, rotation of the image rotator 11 allows the anterior segment of the subject's eye to be observed in a system that is reflected by the light splitting mirror 4. The image does not rotate, and the position from which to observe the anterior segment of the eye can be fixed.

FIG. 2 shows the state of image formation in the image pickup tube of the embodiment shown in FIG.

As described above, according to the present invention, the measurement and observation optical systems are separated, making it possible to perform measurements while observing a wide area of the anterior eye without reducing measurement accuracy, and to understand the state of the eye to be examined and the measurement site during measurement. Moreover, the image planes of the measurement optical system and the observation optical system are the same plane, and the corneal shape can be observed on the observation plane for observing the anterior segment of the eye. It is possible to observe only the shape of the cornea by moving it apart. Further, since the imaging means having the imaging surface is provided on the same surface, the configuration of the apparatus is simplified and the cost is reduced. Furthermore, according to the present invention, the anterior segment observation image is observed at a fixed observation position without being influenced by the image rotation means.

[Brief explanation of drawings]

FIG. 1 is a diagram of an embodiment of the present invention, and FIG. 2 is a diagram of an imaging state in an image pickup tube. In the figure, 1 is a light source, 2 is an annular cylindrical lens, 3 is an objective lens, 4 is a light splitting mirror, 5 is an imaging lens, 6 is an imaging tube, 10 and 13 are mirrors, 1
1 is an image rotator, 12 is a deflection prism, 14 is a reflection prism, Ec is the cornea of the eye to be examined, and Ei
is a corneal reflector, Eii is a corneal reflection image, and l is an optical axis.

Claims (1)

[Claims] 1 It has a chart projection system that projects a chart onto the cornea of the eye to be examined, and a first imaging optical system that forms a corneal reflection image of the chart, and the first imaging optical system includes an image rotating means, an image dividing means, means, in a corneal shape measuring device having an image division amount changing prism and measuring the corneal shape from the amount of movement of the image division amount changing prism until the divided corneal reflection images match, the first imaging optical system; a light splitting member provided in the optical path on the side of the subject's eye from the image rotation means; and a second imaging optics for forming an image of the anterior segment of the subject's eye in the optical path branched by the light splitting member. a corneal reflection system, the image plane of the first imaging optical system and the image plane of the second imaging optical system being the same plane, and image-divided into the anterior segment image area of the subject's eye; A corneal shape measuring device comprising: an imaging means that bends an optical path by a mirror so that image areas are separated from each other, and has an imaging surface on the same surface.