JPH0363027A - Apparatus for ophthalmic measurement - Google Patents

Abstract

PURPOSE:To enable a lens matching with a subject eye to be prescribed by installing a display device for indicating not only an image of anterior part of the subject eye but also measurement informations of ophthalmic refractive power and corneal shape and by making this display device function as a device for selecting the lens. CONSTITUTION:When a measurement switch 37 is pushed after adjusting an image of anterior part of a subject eye E displayed on a TV monitor 44 while observing it, an electronic flash 1 is lighted, a reflection image of cornea Ec formed by this light is thrown on a detection element 10, and output signals from the element 10 are memorized in a RAM 34, after having their waveforms shaped and being converted into digital signals by a processing circuit 30. Next, a light emitting diode 11 is lighted, a chart 13 is projected on an eye ground Ef, its reflected image is thrown on a detection element 22, output signals from the element 22 are memorized in the RAM 34 after having their waveforms shaped and being converted into digital signals by a circuit 31 for processing an ophthalmic refractive power signal. Then an information of corneal shape and that of ophthalmic refractive power are computed by an MPU 32 with specified arithmetic expressions written in a ROM 33 and displayed on the TV monitor 44. Further, a contact lens corresponding to an average radius of corneal curvature is selected out of a list put in an EEROM 36.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ophthalmological measuring device for measuring eye refractive power and corneal shape, which allows selection of a contact lens most suitable for an eye to be examined.

[Prior Art] In recent years, not only glasses but also contact lenses have become widely popular for vision correction.

Hard and soft contact lenses each have their own features in terms of how they correct astigmatism, and hard contact lenses can correct some degree of corneal astigmatism due to the correction effect of the tear film that forms between the lens and the cornea. On the other hand, soft contact lenses follow the curve of the cornea and cannot correct corneal astigmatism.

Although hard contact lenses have these advantages,
This can be a disadvantage in some cases. In other words, in addition to corneal astigmatism, lens astigmatism is a contributing factor to ocular astigmatism, but both of these may compensate for each other, and if a hard contact lens is prescribed to such an eye, only the corneal astigmatism will be corrected. Even if the astigmatism is corrected, the astigmatism of the crystalline lens may surface as residual astigmatism, and the astigmatism may even increase. Therefore, when prescribing contact lenses, not only nearsightedness and farsightedness but also astigmatism in the subject's eye must be carefully considered.

For contact lens prescription, first, the shape of the cornea of the eye to be examined is measured with an instrument called an ophthalmometer or keratometer, the base curve is selected and the amount of corneal astigmatism is determined, and then an objective refraction test is performed using a refractometer, etc. It is common to screen for total eye refractive power and total astigmatism, and then perform a subjective refraction test and final determination of the base curve using the trial lens method.

Regarding the selection of the trial lens necessary at this time, conventionally, the examiner first refers to a separate table etc. based on the average radius of corneal curvature obtained with an ophthalmometer or autokeratometer, and first selects a looser lens. Starting from 100%, the contact lenses are gradually changed to tighter ones to determine which contact lenses suit the eye being examined. However, according to this method, the time and effort required to finally determine an appropriate contact lens are a considerable burden on both the examiner and the subject.

In order to solve this problem, it is known that an ophthalmometer or autokeratometer has a built-in table of contact lenses according to the average radius of corneal curvature, which is selected and printed out using an internal computer. This device has a function to switch between soft contact lenses depending on the degree of corneal astigmatism.

[Problems to be Solved by the Invention] However, in the conventional example described above, a lens is selected as the optimal lens without taking residual astigmatism, that is, the degree of lens astigmatism into consideration, and the examiner cannot clearly recognize the existence of residual astigmatism. That is, if there is a display means that displays the anterior segment image of the subject's eye as well as ocular refractive power measurement information including ocular refractive astigmatism and corneal shape measurement information including corneal astigmatism, the examiner can see the anterior segment image. Knowing that the eye to be examined and the device are aligned, it is possible to clearly recognize the presence of residual astigmatism by determining the consistency between the degree of refractive astigmatism of the eye and the degree of corneal astigmatism, which is impossible in the conventional example.

An object of the present invention is to provide an ophthalmological measuring device that solves the above-mentioned problems of the conventional method, and its gist is to project a light beam onto the fundus of the eye to be examined, detect the reflected light from the fundus, and measure the eye refractive astigmatism. a first measuring means for detecting ocular refraction measurement information including;
a second measuring means for projecting a light beam onto the cornea of the eye to be examined and detecting the corneal reflected light to detect corneal shape measurement information including corneal astigmatism; the first measuring means and the second measuring means; In an ophthalmological measuring device, the ophthalmological measuring device has a lens selection means for selecting a lens suitable for the eye to be examined, including a contact lens, based on the measurement information, and eye refractive power measurement information including the eye refractive astigmatism along with an anterior segment image of the eye to be examined; There is a patent that further comprises a display means for displaying corneal shape measurement information including the degree of corneal astigmatism, and the display means functions as the lens selection means.

[Example] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows an optical system showing an embodiment of the present invention. During corneal shape measurement, visible light emitted from a ring-shaped strobe 1 is directed to a collimator ring lens 2 facing the subject's eye E.
A circular slit 3 provided in the slit 3 is illuminated. The slit 3 is located on the focal plane of the ring lens 2 when viewed in a cross section including the optical axis, and the slit 3 is optically located at an infinity point, so that the light projected from that infinity point is illuminated. The cornea Ec of the optometrist E is illuminated. Since the surface of the cornea Ec is like a convex mirror, it creates a corneal reflection image of the slit 3, and this corneal reflection image reflects only near-infrared light through the objective lens 4, and rejects light of other wavelengths. It passes through a dichroic mirror 5 that transmits light, is reflected upward by a dichroic mirror 6 that reflects visible light and transmits infrared light, is reflected to the right by a beam splitter 7, and then passes through a multiple diaphragm 8 and a prism 9. It is deflected and reimaged onto a one-dimensional position detection element io made of a CCD (charge coupled device).

The multi-hole aperture 8 is, for example, 5 as shown in FIG.
The prism 9 also has an opening 8a to 8e.
It has five elements 9a to 9e as divided by dotted lines corresponding to elements 9a to 8e, and each of these elements 9a to 9e
has a cross-sectional shape as shown in Figure 2 (bl).

5 separated by this multi-hole aperture 8 and prism 9.
The corneal reflection images are combined at the position of the detection element 10 in the relationship shown in FIG. In FIG. 3, sb represents a corneal reflected image obtained by forming and separating an image reflected by the cornea Ec by the objective lens 4, and 10a to 10e are detection elements, respectively, and apertures 8a to 8e, a prism It corresponds to each of elements 9a to 9e. As a result, the coordinates of five points in the corneal reflection image sb are detected, and the simultaneous equations are solved by substituting the coordinates of these five points into the general formula of the quadratic curve, AX2-13xy+cy"+DX+EY+F=0. Find the coefficients A to E by
General formula of ellipse, (x xol” / a” + (y y012
/ b2= Matadashi, x=Xcosθ−Y sinθ
The astigmatism axis can be calculated from the angle θ by transforming the ellipse into y==X sin θ+Y cos θ, deriving the radius of curvature of both the main warps of the cornea Ec from the major axis a and the minor axis of the ellipse.

On the other hand, in the case of refractive power measurement, as shown in FIG.
2 to illuminate the fundus projection chart 13. As shown in FIG. 4, this chart 13 is provided with three slits 13a to 13c in three meridian directions that form an angle of 120 degrees with each other. light emitting diode 11
The light further passes through the relay lens 14, forms an image on the fundus illumination diaphragm 15, passes through the perforated mirror 16, passes through the guichroic mirror 6 because it is infrared light,
Only the far-infrared light passes through the dichroic mirror 5, and is further imaged on the pupil of the eye E to be examined via the objective lens 4, thereby illuminating the fundus Ef.

The image of the chart 13 created by this far infrared light is the relay lens 1
4 and is once formed into an image, and projected by the objective lens 4 so as to be conjugate with the fundus of the emmetropic eye.

The reflected image from the decoy bottom Ef passes through the objective lens 4 again, passes through the dichroic mirror 5.6, forms an image, and is reflected downward by the perforated mirror 16. A diaphragm plate 17 is disposed near the perforated mirror 16, and this diaphragm plate 17 has six apertures 17a to 17f each consisting of an annular transmitting portion, as shown in FIG. The openings 17a and 17d, 17b and 17e, and 17c and 17f correspond to each other and form one channel. 6th
The image is formed as shown in 15A and 17A in the figure, and the chart 13
The image is separated into a projection optical system and a measurement optical system.

The light beam divided by the aperture plate 17 passes through the imaging lens 18, is separated by the prism 19, passes through the mirror 20 and the cylindrical lens 21, and is condensed in the transverse direction of the detection element 22. The image is formed on 22c. The prism 19 has six elements 19a to 1.9f as shown in FIG. 7 (bl indicates the cross-sectional shape of the prism 19).

The images separated in this way are focused in the longitudinal direction of the images by three cylindrical lenses 21a to 21c and formed on detection elements 22a to 22c, as shown in FIG.
Fundus images Pa-Pf correspond to the openings 17a to 17f.

If the eye E to be examined is an ametropic eye, the light ray that exits from the fundus Ef and exits at a single point above the pupil will be emitted at an angle that corresponds to the refractive power, so an optical system like the one in this example is used. By doing so, the distance between the two fundus images P on the detection element 22 changes depending on the refractive power of the eye E to be examined.

Therefore, if the relationship between the distance between the two fundus images P and the refractive power is determined in advance, the refractive power in the three radial directions can be measured, and each refractive power can be substituted into the following equation, D=A sin (2ω + θ) + B. The spherical power, astigmatic power, and astigmatic angle can be calculated using The variables D and ω represent the refractive power and the radial angle, respectively, and the constants A, B, and θ represent the degree of astigmatism, respectively.
Corresponds to the average refractive power and astigmatism axis.

The alignment between the eye E and the instrument is achieved by using near-infrared light emitted from a light source (not shown) from the anterior segment of the eye, which is emitted from the objective lens 4 and reflected downward by the guichroic mirror 5.
This can be done by forming an image of the anterior eye on the television image pickup tube 24 using the television relay lens 23, and displaying the anterior eye image on a television monitor attached to the main body or provided separately.

Furthermore, an eye refractive power measurement target 25 is movably provided above the beam splitter 7 together with an illumination light source 26 , and the fixation target 25 illuminated by the illumination light source 26 is exposed via a relay lens 27 and the beam splitter 7 . The eye to be examined E is gazed at by the optometrist E, and the eye E to be examined is fixed.

Further, one end of the fiber 28 serves as a fixation target for corneal shape measurement, and a prism 9 is located at the emmetropic eye position of the fundus Ef of the eye E to be examined.
A light emitting diode 29 that emits visible light is arranged near the other end. When measuring the shape of the cornea, the light emitting diode 29 is turned on and the fiber 28 arranged at the center of the prism 9 emits light, so that the eye to be examined E
A clear bright spot can be observed, and the eye E to be examined is fixed. Note that, depending on the type of fixation target 25, by moving the fixation target 25 to the eye refractive power measurement position measured by this device, it can also be used as a same visual target for corneal shape measurement.

FIG. 9 is a block circuit diagram of the electric control circuit, and the same reference numerals as in FIG. 1 represent the same members. here,
Corneal shape signal processing circuit 3 that inputs the signal of the detection element 10
0, an eye refraction signal processing circuit 31 that inputs the signal of the detection element 22, a microprocessor unit (hereinafter referred to as MPU) 32 that performs arithmetic control, a read-only memory (hereinafter referred to as ROM) 33, and a first A random access memory (hereinafter referred to as RAMI) 34, a second random access memory (hereinafter referred to as RAMII) 35 that stores information about contact lenses, and a table that stores a table corresponding to the average radius of corneal curvature of contact lenses. A rewritable electrically eraseable read-only memory (hereinafter referred to as EEROM) 36 and a corneal shape signal processing circuit 3o
and the eye refraction signal processing circuit 31, both circuits 3o, 3
1 switching control is performed, and the measurement switch 37 and light source 1 are also controlled.
1. An interface (hereinafter referred to as IF) 39 connected in parallel with the strobe drive circuit 38 connected to the ring-shaped strobe 1; and an input device 40 for manually inputting data when editing a contact lens table; A serial interface (hereinafter referred to as SIF) 4 is connected as necessary to a display 41 that displays selected contact information.
2; a printer 43 that prints out the measurement results and selected contact lens information; and a printer 43 that prints out the measurement results and the external silver information output from the television camera 24 and prints them on the television monitor 4;
A video random access memory (hereinafter referred to as VRAM) 46 which is connected to a mixer (hereinafter referred to as MIX) 45 and which stores measurement results are connected to an internal bus 47 in parallel.

When performing a measurement, first, adjustments are made while viewing the external silver, that is, the anterior segment image of the eye E to be examined, which is displayed on the television monitor 44, and then the measurement switch 37 is pressed.

Then, the strobe drive circuit 38 is activated by a signal from the IF 59, and the ring-shaped strobe 1 emits light. A corneal reflection image formed by this light emission is focused on the detection element 10, and the signal output from the detection element 10 is waveform-shaped by a corneal shape signal processing circuit 30, and then an amplifier (not shown) and an A/
It becomes a digital signal amplified by a D converter and is stored in RAM.
It is stored in l34. Next, the light emitting diode 11 is caused to emit light to project the chart 13 onto the fundus Ef, and a reflected image from the fundus Ef is formed on the detection element 22. Detection element 22
The output signal is waveform-shaped by the eye refraction signal processing circuit 31,
The digital signal is amplified by an amplifier and an A/D converter (not shown) and is stored in the RAM 134. When the reflected image signals from the cornea Ec and the fundus Ef are taken into the RAM 134, the MPU 32 calculates corneal shape information such as maximum radius of curvature, minimum radius of curvature, average radius of curvature, Corneal astigmatism, astigmatism axis angle, and eye refractive power information such as spherical refraction, eye refraction astigmatism,
Calculate the astigmatism axis angle and store the result in VRAM46, MIX
45 and is displayed on the television monitor 44. continue,
Contact lenses that correspond to the average corneal radius of curvature are EER
It is selected from the table input into OM36.

FIG. 10 shows an example of the screen of the television monitor 44, in which the image of the anterior segment of the eye E to be examined is projected on the upper part of the screen, and the various corneal shape information and eye refractive power information described above are displayed on the lower part. It is now displayed. As a result, the examiner sees the anterior segment image and knows that the eye to be examined E and the device are aligned, and clearly identifies the presence of residual astigmatism by determining the consistency of the degree of refractive astigmatism of the eye and the degree of corneal astigmatism. can be confirmed.

FIG. 11 is a diagram displaying contact lenses from various companies classified by the average corneal radius of curvature AVH. For example, for each average corneal radius of curvature AVH, hard contact lenses are from companies A to D, and soft contact lenses are from companies E to F. An example of a company registered as a company is shown below. Now, if the calculated average corneal radius of curvature AVR is 8.56 mm, the row indicated by the arrow - in FIG. 11 will be selected.

Next, the degree of lens astigmatism Cr obtained by subtracting the degree of corneal astigmatism Ck from the degree of refractive astigmatism Cf and its axis angle AXr are determined by the following equation.

AXr = (1/2] jan-'((Cf 5in
2AXf-Ck 5in2AXk) / (Cf cos2AXf -Ck cos2AXk
) )Cr = (Cf 5in2AXf - Ck 5
in2AXk)/sin 2AXr where AXf is the axial angle of ocular refractive astigmatism, and AXk is the axial angle of corneal astigmatism.

Using the crystalline lens astigmatism cr and the ocular refractive astigmatism Cf obtained in this way, it is determined whether to select a hard contact lens or a soft contact lens.

Figure 12 shows the ROM3 for determining whether to select hard contact lenses or soft contact lenses.
3 shows a flowchart to be memorized, where L represents the type of contact lens, L=H is a hard contact lens, L=S is a soft contact lens, L=A
LL indicates that hard or soft contact lenses have been selected. Further, F is a flag indicating whether or not astigmatism can be corrected, and F=O means that correction is possible, and F=1 means that astigmatism cannot be corrected. Furthermore, A is a value indicating the magnitude of astigmatism that determines the selection of contact lenses, and is usually 2 to 3.
A geobuta is input, and this value can be changed using the input device 40.

Next, to explain the procedure for creating this flowchart diagram,
If Cr≦A and Cf≦A, both the lens astigmatism Cr and the eye refractive astigmatism Cf are small, and the corneal astigmatism Ck is also small. Therefore, when a hard contact lens is used, the corneal astigmatism Ck is corrected and the astigmatism depends on the lens astigmatism Cr, but since the lens astigmatism Cr is small, there is no problem. Further, when a soft contact lens is used, corneal astigmatism Ck is not corrected, but since the ocular refraction or astigmatism Cf is small, this also poses no problem.

If Cr≦A, Cf>A, lens astigmatism C
Since r is small and the eye refractive astigmatism Cf is large, the corneal astigmatism Ck is large, and the corneal astigmatism Ck can be corrected with a hard contact lens. Therefore, Cr≦A,C
When f>A, hard contact lenses can be used <L=H.

If Cr>A and Cf≦A, the lens astigmatism Cr is large and the eye refractive astigmatism Cf is small, so the corneal astigmatism Ck and the lens astigmatism Cr cancel each other out,
A soft contact lens may be used to preserve the degree of corneal astigmatism Ck, and in this case, L=S.

If Cr>A, Cf>A, lens astigmatism C
Since r and ocular refractive astigmatism Cf are both large and corneal astigmatism Cr is small, it is inappropriate to correct astigmatism with contact lenses. However, it makes sense to prescribe contact lenses to correct spherical refractive power, and if Cf≧Cr at that time, the degree of corneal astigmatism Cr is small but has surfaced, so hard contact lenses can be used. If Cr>Cf, corneal astigmatism is considered to be correcting lens astigmatism, so soft contact lenses may be used to avoid removing this effect.

That is, if Cr>A, Cf>A, Cf≧Cr, then L=H, Cr>A %Cf>A %Cr
> Cf, then L=S.

The above results are shown in a flowchart as shown in the above-mentioned FIG. 12, and FIG. 13 shows an example of the output results of the contact lenses determined in this way and finally selected. Figure 13 (a) shows the case where L = ALL, where both hard and soft contact lenses can be used, and (b) shows the case where L = H, where hard contact lenses are suitable, fc)
shows the case where F=1 and L=S for which soft contact lenses are suitable. In these examples, the suitability and disapproval are indicated by characters on the screen, but they may also be output in letters or the like. This output result can be output to a printer 43 or a television monitor 44. If necessary, it may be output to both the printer 43 and the television monitor 44.

At the same time, this output result is stored in the RAMll35. Then, if necessary, connect the display 41 to the 5IF 42 and press the switch 41a of the display 41 to
The information stored in l35 can be output to display 41 and used when prescribing contact lenses remotely from this device.

In addition, in this example, when selecting between hard contact lenses and soft contact lenses, lens astigmatism Cr
However, the flowchart could also be rewritten to start the selection from the corneal astigmatism Ck, then compare the lens astigmatism Cr, and finally the ocular refractive astigmatism Cf. good.

In the above description, the case where the corneal shape information is used to select a contact lens has been described in detail, but it is clear to those skilled in the art that the corneal shape information can also be used to select a spectacle lens. In other words, when corneal shape information is detected as having a very large degree of residual astigmatism, contact lenses cannot be used and eyeglass lenses are targeted, and the present invention can be used to take the residual astigmatism into consideration and create eyeglass lenses that are optimal for the eye to be examined. may be prescribed.

[Effects of the Invention] As described above, according to the ophthalmological measuring device according to the present invention, the examiner can recognize residual astigmatism and prescribe lenses suitable for the eye to be examined, including contact lenses.

[Brief explanation of drawings]

The drawing shows an embodiment of the ophthalmological measuring device according to the present invention,
Fig. 1 is a diagram of its optical configuration, Fig. 2 is a front view of the multi-hole diaphragm, (b) is a cross-sectional view of the prism, and Fig. 3 is an illustration of the relationship between the corneal reflection image and the detection element. Figure 4 is a front view of the fundus projection chart, Figure 5 is a front view of the aperture plate for measuring eye refraction,
FIG. 6 is a front view of the image formation state of the aperture on the pupil of the eye to be examined, FIG. 7(a) is a front view of the circular image separation prism for measuring eye refractive power,
(bl is its cross-sectional view, FIG. 8 is an explanatory diagram of the relationship between the fundus image and the light receiving element, FIG. 9 is a block circuit diagram of the electrical II+ control circuit, and FIG. 10 is an explanatory diagram of the display on the TV monitor. Fig. 11 is an explanatory diagram of the contact lens selection table written in the EEROM, Fig. 12 is a flowchart for selecting the type of contact lens, and Fig. 3 is an explanatory diagram of the output result of the selected contact lens. The symbol l is a ring-shaped strobe, 2 is a ring lens, 3 is a slit, 4 is an objective lens, 5.6 is a dichroic mirror, 7 is a beam splitter, 8 is a multi-hole aperture, 9.19
is a prism, 10.22 is a detection element, 11.29 is a light emitting diode, 13 is a chart, 15 is an illumination diaphragm, 16 is a perforated mirror, 17 is a diaphragm plate, 21 is a cylindrical lens, 24 is a television image pickup tube, and 25 is a fixed optotype, 26 a light source, 28 a fiber, 3o a corneal shape signal processing circuit, 31
is an eye refraction signal processing circuit, 32 is an MPU, 33 is a ROM,
34 and 35 are RAM, 36 is EEROM, 37 is a switch, 38 is a strobe drive circuit, 39 is an IF, 4o is an input device, 41 is a display, 42 is an SIF, 43 is a printer,
44 is a television monitor, 45 is a MIX, and 46 is a VRAM.

Claims (1)

[Claims] 1. A first method for projecting a light beam onto the fundus of the eye to be examined and detecting the reflected light from the fundus to detect eye refraction measurement information including eye refraction astigmatism.
a second measuring means that projects a light beam onto the cornea of the eye to be examined and detects the corneal reflected light to detect corneal shape measurement information including corneal astigmatism; the first measuring means and the first measuring means; and a lens selection means for selecting a lens suitable for the subject's eye, including a contact lens, based on the measurement information of the second measuring means. An ophthalmological measurement device comprising a display means for displaying refractive power measurement information and corneal shape measurement information including the corneal astigmatism degree, the display means functioning as the lens selection means. 2. The lens selection means calculates the degree of astigmatism of the crystalline lens, and compares the degree of astigmatism of the crystalline lens and the degree of refractive astigmatism with each other or with predetermined values, and selects a soft contact lens or a hard contact lens suitable for the eye to be examined. The ophthalmological measuring device according to claim 1, further having a function of selecting a contact lens. 3. The ophthalmological measuring device according to claim 2, wherein the lens selection means selects several types of lenses from registered contact lenses based on average corneal curvature radius information. 4. The scope of the present invention is that the lens selection means selects a lens whose range is further narrowed from among several types of lenses selected previously based on the degree of refractive astigmatism and the degree of corneal astigmatism as a second step. The ophthalmological measuring device according to item 3. 5. The ophthalmological measuring device according to claim 3, wherein the lens selection means is capable of editing registered contact lens information such as correction and addition. 6. The ophthalmological measuring device according to claim 2, wherein the lens selection means is capable of storing output results.