JPH09224908A - Target for eidoptometry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a target which provides accurate eidoptometry results by a general inspection without any element to be judged by difference in small/ large sizes and has no directivity by forming black rings whose target units are independent and a composite ring having an independent black circle inside the black ring. SOLUTION: Edoptometry targets are constituted by a combination of four target units in total, for example, three independent black rings and a composite ring 2 having an independent black circle 2b inside the black ring 2a. The independent black rings 1 have doughnut shapes of Randolt ring without any break, the outer diameters of this black rings 1 and the outer diameter of the black ring 2a of the composite ring 2 are set to the same size, and the areas of the independent black rings 1 and the black part of the composite ring 2 are set to equal. The arrangement state is so set that the adjoining interval of the four target units which are positioned in the equal distance from an intersection point of orthogonal lines and have the centers on the orthogonal lines have the same interval to the target units.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optotype used for a visual acuity test.

[0002]

2. Description of the Related Art The Landolt ring, which is a reference target, is well known as a target for visual acuity test that has been commonly used. The Landolt ring has cuts at any of the top, bottom, left, and right of the ring, and it naturally has directionality. In addition to Landolt's rings, character and numerical targets are also used supplementarily, but when considered as figures, they all have directionality.

[0003]

As described above, in the Landolt ring which is used as a reference target, in addition to the character target and the numerical target that are used as auxiliary targets, the targets that have been conventionally used are Also has directionality, and therefore, even if the targets that represent the visual acuity at the same stage have the same size in the Landolt ring, the identification threshold value varies depending on which target is determined. Not only does the judgment result differ in one step, but this fluctuation is large especially when there is astigmatism.
It is not uncommon for some targets to be easier to determine, even though it is difficult to determine which one has higher visual acuity in two or three steps. That is, the determination result changes as the direction of the target changes. For this reason, in order to accurately measure visual acuity using the Landolt ring, it is necessary to seek judgment for multiple targets that have different directions in one visual acuity stage, and to investigate the highest stage that can correctly determine more than half of them. However, the inspection took time and was troublesome.

Therefore, in order to measure the visual acuity more easily and more accurately, the inventor uses a non-directional visual target to at least theoretically determine the visual acuity. I have been earnestly researching what I cannot make a mark.

As one measure, after examining the graphic properties of the numbers from 0 to 9, the number is set to 3 based on a certain law.
We developed and commercialized a visual acuity chart that uses a combination of each of them as one optotype, but the direction has not completely disappeared, and there is the drawback that it is not suitable for children who do not know the letters well. It was

In order to solve these difficulties, the inventor has
In Japanese Patent Application No. 7-271287, we provided an improved target consisting of a combination of a circle with a white central part and a circle with a black part as a whole, but for the subject, an element to judge the white circle and the black circle by the size difference Due to the relationship, there is a possibility that the value may be theoretically higher than the visual acuity due to the Landolt ring when there is a certain degree of regular astigmatism.

Therefore, the object of the present invention is to:
It is an object to provide an optotype without directivity that can obtain an accurate visual acuity measurement result by a single examination without the factor of judging by size difference.

[0008]

In order to achieve the above object, the inventor basically employs a circle as a figure having no directionality as a target unit, as in the previous application. However, when two types, a white circle and a black circle with the inside filled in, are used as the target units, the problems described above were added and improvements were made to this, and an independent black ring and an independent black ring Two types of composite rings having black circles are used as the target unit.

That is, in the optotype for visual acuity test according to the present invention, the optotype unit is composed of an independent black ring and a composite ring having an independent black circle inside the black ring. It is characterized by combining at intervals.

As for the shape, the independent black ring has a donut shape without the break of the Landolt ring, and the outer diameter of the black ring of the composite ring combined with this is equal to the outer diameter of the independent black ring,
It was concluded that it is appropriate to set the areas of the black parts of the independent black ring and the complex ring to be equal.

The size of the new visual target at each visual acuity stage is repeated as a result of a basic experiment to find a size at which the discrimination threshold is equal to that of the Landolt ring. It was concluded that it is appropriate for the visual target corresponding to the above to be 56% of the outer diameter of the Landolt ring in the outer diameter of the independent black ring.

When an independent black ring and a composite ring each having an independent black circle inside the black ring are combined at appropriate intervals and used as a single target, the probability of accidental probability is high. It is halved and it is thought that accuracy is lacking. In order to prevent this defect, three or more optotype units are arranged vertically and horizontally at regular intervals, and
It is desirable to use a combination in which only one is a black ring or a composite ring as one target. However, when the number is 5 or more, the chance value is low, but on the other hand, there is a problem in that it takes time for the examinee to respond and the area of the target is too large. It can be said that 3 or 4 optotype units are preferable for the purpose of quickness and accuracy of examination.

If the spacing between the independent black ring and the composite ring having an independent black circle inside the black ring is arranged vertically and horizontally, if the space is made too small, the optotype unit next to the black ring will affect the distance. While the premise of simply distinguishing each one is broken,
If the interval is set larger than necessary, there is a problem that the area of one target is too large. In the case of an optotype using four optotype units, as a preferable interval, the adjoining intervals of four optotype units having the center on the orthogonal line at the same distance from the intersection of the orthogonal lines have the same interval as the optotype unit. It is desirable to arrange as many as possible for quick and accurate inspection.

[0014]

DETAILED DESCRIPTION OF THE INVENTION A description will be given below with reference to the accompanying drawings. FIG. 1 shows an example of an optotype for visual acuity test according to the present invention, which includes a total of four independent black rings 1 and a composite ring 2 having an independent black circle 2b inside one black ring 2a. It is composed of a combination of two optotype units. Independent black ring 1
Is a donut shape without the break of the Landolt ring, the outer diameter of the black ring 1 and the outer diameter of the black ring 2a of the composite ring 2 are equal, and the areas of the black portions of the independent black ring 1 and the composite ring 2 are equal. I am trying to become. In the arrangement state, four optotype units having the center on the orthogonal line at the same distance from the intersection of the orthogonal lines are arranged so that the adjacent intervals are the same as the optotype unit. That is, the adjoining interval of the target unit is twice the outer diameter of the target unit.

FIG. 2 shows an example of a base of a visual acuity table prototyped using this optotype. Landolt rings are arranged in two columns on the left side so that the visual acuity by only the Landolt ring can be measured. In this case, the highest stage that can discriminate both of the same stages is measured, and this is determined as the visual acuity by the Landolt ring. Because of the size, 0.1 and 0.2 are Landolt rings as they are, and 3 or more of 0.3 or more using this target.
The row also has three circles from 0.3 to 0.6. The arrangement interval in this case is also the same as in the case of four circles, and has a configuration in which two black rings 1 and one composite ring 2 are arranged in a mountain shape. The direction of the break of the Landolt ring is deliberately not to be common to the two stages. That is, if one of the cuts is above or below, the other is left or right. Diagonal cuts are not used. In each stage, the target has a size of 56% of the outer diameter of the Landolt ring in the outer diameter of the independent black ring 1.

In FIG. 3, (A) is a part of the prototype visual acuity table base, and (B) is a photograph taken by a camera of myopic astigmatism. Looking at the Landolt ring, it is easy to determine the "rightward cut" at the top, but it is difficult to determine the "downward cut" target below it. However, it is possible to determine the "rightward break" below it. In other words, it indicates a state in which it is possible to make a "jump over" decision. On the other hand, with this target, it becomes more difficult to read as it goes downward, indicating that it is suitable for the original visual acuity measurement. That is, it is possible to recognize the characteristic that the "jumping phenomenon" cannot occur when the target does not have directionality, and can occur when the target has directionality.

Even when the visual acuity is actually measured, for example, with the Landolt ring, it is difficult to determine the downward cut of 0.6, but the lateral cuts of 0.7 and 0.8 are correctly answered. The phenomenon of "jumping over" is sometimes experienced. This phenomenon is particularly remarkable when there is astigmatism, and it can be said in theory that such a "judgment of a smaller target more accurately" occurs. On the other hand, in the case of the new target, there is no threshold change depending on the direction,
At least in theory, such a "jumping phenomenon" cannot occur. In fact, even in the process of measuring visual acuity using prototypes, no such "jumping" was observed in the test using only this target, and this target is also superior in terms of the ease of the test. I confirmed that.

In order to confirm that this target is highly practical and useful, a visual acuity measurement value using only the new visual target and a measurement value using only the Landolt ring are compared using the prototype visual acuity table base. An experiment was conducted. Regarding the new visual target, we adopted a method of answering where there is only one compound ring.

When the results of the visual acuity measurement using only the Landolt ring alone and the results of the visual acuity measurement using only the new visual target were compared for 208 eyes, the results shown in Table 1 were obtained. Table 2 shows the same result in terms of distribution ratio.

[0020]

[Table 1]

[Table 2] As is clear from Table 1, when viewed as a whole, 63% of the measured values were in agreement. Originally, the visual acuity itself is continuous rather than stepwise, and considering that it tends to constantly fluctuate under minute conditions, it can be considered that one step of vertical difference naturally occurs. Therefore, if the difference between plus and minus one stage is regarded as common, 97% of the visual acuity by the new visual target
Shows that the result is similar to that of the Landolt ring.

The target can be used not only as a target for a visual acuity chart as shown in FIG.
It is needless to say that it can be used as a single optotype such as a liquid crystal type, and it is needless to say that it is not limited to an example in which it is printed on a base when constructing an eye chart.

[0022]

As described in detail above, the optotype for visual acuity test according to the present invention has an independent black ring and a complex ring having an independent black circle inside the black ring as a target unit, and this is suitable. It is a target that can be accurately judged even when there is astigmatism because there is no directionality, there is no "jump over phenomenon" in the visual acuity test, because it is combined at intervals and one of them is judged. is there. In addition, it provides an extremely reliable visual acuity test target that allows quick, accurate and easy visual acuity testing without the need for time-consuming explanations to the examinee and because it does not involve factors that make a difference in size. It was possible.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a visual acuity test index according to the present invention.

FIG. 2 is a front view showing an example of a visual acuity table base configured by combining a target and a Landolt ring.

FIG. 3A is a front view showing a part of the same visual acuity table base.
(B) is a front view of a photograph taken by a myopic astigmatism camera.

[Explanation of symbols]

1 ... Black ring 2 ... Composite ring 2a ... Black ring 2b
...... Black circle

Claims (4)

[Claims] 1. A target unit is composed of an independent black ring and a composite ring having an independent black circle inside the black ring, and the black ring and the composite ring are combined at an appropriate interval. A visual acuity test target. 2. The independent black ring is a donut shape without the break of the Landolt ring, and the outer diameter of the black ring of the composite ring combined with this is equal to the outer diameter of the independent black ring, and the black ring of the independent black ring and the black of the complex ring is independent. The optotype for a visual acuity test according to claim 1, wherein the areas of the parts are determined to be equal. 3. An optotype for visual acuity test according to claim 1, wherein three or more optotype units are arranged vertically and horizontally at regular intervals, and only one of them is a black ring or a composite ring. . 4. The target corresponding to a Landolt ring representing a certain level of visual acuity has a size of 56% of the outer diameter of the Landolt ring in the outer diameter of the independent black ring.
The visual acuity test target described.