JPH0580206B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention deforms the cornea by blowing an air flow onto the cornea of the eye to be examined, and measures the intraocular pressure by optically detecting the deformation. This relates to a non-contact tonometer.

[Prior Art] Conventionally, in this type of tonometer, it is photoelectrically detected whether or not the corneal reflected light of the alignment detection light beam is in the airflow direction coaxial with the optical axis, and if the reflected light and the optical axis are If the working distance is off, or if the reflected light is not focused on the photoelectric conversion element, the air blowout is stopped.
Therefore, alignment and working distance adjustment are extremely delicate. Conventional examples include JP-A-60-83642 and JP-A-61-196935, but both require delicate alignment and working distance adjustment to obtain accurate measurement values. be.

[Object of the Invention] The object of the present invention is to correct alignment and working distance adjustment even if the accuracy is slightly low by correcting measured values using position detection signals such as alignment and/or working distance signals. To provide a tonometer that can perform accurate intraocular pressure measurement, is extremely easy to align, and has high accuracy.

[Summary of the invention] The gist of the present invention for achieving the above object is as follows:
A tonometer that optically detects corneal deformation by blowing an airflow onto the cornea of the eye to be examined uses a tonometer that optically detects corneal deformation by blowing an airflow onto the cornea of the eye to be examined. Deformation detection means for detecting corneal deformation information based on received light; and position detection for detecting positional information of the eye to be examined when the deformation detection means obtains the deformation information based on reception of corneal reflected light from the eye to be examined. and a correction means for correcting the intraocular pressure measurement value obtained from the detection result of the deformation detection means based on the detection of the position detection means.

[Embodiments of the Invention] The present invention will be described in detail based on illustrated embodiments.

FIG. 1 shows a first embodiment, where E represents the eye to be examined and Ec represents the cornea. A light beam for deformation detection is projected from a light source 1 through a lens 2 toward the cornea Ec of the eye E to be examined, and the reflected light from the cornea is received by a photoelectric conversion element 4 through a lens 3. On the other hand, the alignment detection light beam is projected from the light source 5 through the lens 6, the light splitting member 7, and the lens 8 to the center of curvature of the cornea Ec.
When Ec is at a predetermined position, the light returns along the same optical path, passes through the light splitting member 7 and the lens 9, and reaches a photoelectric conversion element 10, such as a two-dimensional semiconductor optical position sensor. Further, compressed air obtained by a cylinder mechanism consisting of a cylinder 11 and a piston 12 is blown toward the cornea Ec from a nozzle 13 arranged on the optical axis L.

The airflow direction coincides with the optical axis L, and when the cornea Ec is applanated as shown by the dotted line by this air blow, the signal from the photoelectric conversion element 4 becomes maximum, so the intraocular pressure is determined from the air pressure at that time. can be found. In addition, since the corneal reflected light of the alignment detection light beam emitted from the light source 5 reaches the center position of the photoelectric conversion element 10 when the cornea Ec is at a predetermined position, it is transmitted to the air by the signal from the photoelectric conversion element 10. It is possible to detect the degree to which the flow and the center of corneal curvature are eccentric, and alignment adjustment can be performed accordingly. If air is blown in an eccentric state, a portion of the airflow escapes to the side, resulting in little deformation of the cornea Ec and the intraocular pressure being measured as apparently high. However, the relationship between eccentricity and this apparent increase in intraocular pressure is constant, so if you calculate this in advance and correct it, even if there is a slight eccentricity, you can obtain accurate measurements if you know the amount of eccentricity. I can do it.

FIG. 2 shows a second embodiment of the invention, in which the same reference numerals as in FIG. 1 represent the same or equivalent parts. In this second embodiment, in addition to alignment, that is, eccentricity, it is also possible to correct errors in the working distance, that is, in the optical axis direction. Furthermore, information on the deformation of the cornea Ec and information on the alignment and working distance when the airflow is blown can be obtained using the common light source 15 and photoelectric conversion element 16. In this case, since the light source 15 is placed at the focal point of the lens 17, the light beam from the light source 15 passes through the lens 17, becomes parallel, and hits the cornea Ec with a light source image 15.
form a. The reflected light from the cornea Ec is reflected by the lens 8,
The light passes through the light splitting member 7, the lens 18, and the cylindrical lens 19, and enters the so-called four-leaf photoelectric conversion element 16 in which four elements are arranged vertically and horizontally in a ``field'' shape. This four-leaf photoelectric conversion element 16 has four mutually independent light receiving elements 16a to 16d, as shown in FIG.
Signals can be taken out from 6a to 16d.

When the alignment and the working distance both match, the image 15b of the light source image 15a described above is the third image.
As shown in Figure a, it is circular and reaches the center of the four-leaf photoelectric conversion element 16. If the working distance is off, the third
It has an elliptical shape as shown in Figures b and c. Furthermore, if the position of the photoelectric conversion optical element 16 is shifted,
As shown in the figure, the four-leaf photoelectric conversion element 16 is shifted from the center. Therefore, the four light receiving elements 16a to 1
Alignment and working distance can be detected by signals from 6d.

On the other hand, if the working distance is closer than the predetermined distance, the pressure due to the airflow will be stronger, so if no correction is performed, the apparent intraocular pressure will be lower than the actual one. The pressure will be higher than it actually is. However, since the relationship between such deviations in working distance and corneal deformation is constant, if this relationship is determined in advance and corrected, accurate measurements can be obtained even if there is a slight deviation in working distance. is obtained.

Regarding the deformation information of the cornea Ec, when the cornea Ec is deformed by the airflow, the conjugate relationship of the light source image 15a also collapses, so no light flux enters the four-lobed photoelectric conversion element 16, and the intraocular pressure can be calculated from the air pressure at this point. You can ask for it. It goes without saying that the signal from the image 15b just before the cornea Ec deforms can be used as information on alignment and working distance.

[Effects of the Invention] As explained above, the tonometer according to the present invention can correct corneal deformation information by detecting the position detection means, so even if the alignment and working distance adjustment are somewhat rough, the accuracy can be improved. High intraocular pressure can be measured, and alignment of the eye to be examined and the device becomes easy.

[Brief explanation of the drawing]

The drawings show an embodiment of the tonometer according to the present invention, and FIG. 1 is an optical layout diagram of the first embodiment;
FIG. 2 is an optical layout diagram of the second embodiment, and FIG. 3 is an explanatory diagram of the relationship between the photoelectric conversion element and the light source image in the second embodiment. Codes 1, 5, 15 are light sources, 2, 3, 6, 8,
9, 17, and 18 are lenses, 4 and 10 are photoelectric conversion elements, 7 is a light splitting member, 11 is a cylinder, 12 is a piston, 13 is a nozzle, 16 is a four-leaf photoelectric conversion element, and 19 is a cylindrical lens.

Claims (1)

[Scope of Claims] 1. In a tonometer that optically detects the deformation of the cornea by blowing an airflow onto the cornea of the eye to be examined, a deformation detection means that detects corneal deformation information based on the reception of corneal reflected light from the eye to be examined. and a position detection means for detecting positional information of the eye to be examined when the deformation detection means obtains the deformation information based on reception of corneal reflected light from the eye to be examined, and intraocular pressure obtained from the detection result of the deformation detection means. A tonometer comprising: a correction means for correcting a measured value based on detection by the position detection means. 2. The tonometer according to claim 1, wherein the deformation detection means and the position detection means have a common light source and a photoelectric conversion element.