JPS6025202Y2 - Astigmatism test chart - Google Patents

Description

[Detailed description of the invention] The present invention relates to the display of radiation on an astigmatism test chart, and particularly relates to an astigmatism test chart in which the bar lines arranged in a radial pattern are made into broken lines, gradually tapered, and the intervals are gradually narrowed. It is related to.

Although there are various tables for testing astigmatism (astigmatism charts), the radiation astigmatism test chart is the most common and widespread.

The type of radiation astigmatism test chart has radiation (solid lines) placed at 10 degree intervals, and a different color is attached to the outer frame of each 30 degree, allowing the examinee to judge whether the lines are dark or light based on the color. A device that can be easily adjusted using a finger (Ishihara type astigmatism chart)
There is also a system in which the radiation is made into a broken line so that patients with astigmatism can distinguish shades more accurately and clearly (Nakajima type astigmatism chart), and there is also a system in which a black target is displayed on a white background. hand,
Methods such as a white optotype on a black background (over-the-head astigmatism test chart) have been considered, but test results may vary due to the slow reaction of some subjects and the fact that the chart itself is difficult for the subject to read. They tended to lack trust.

In other words, whether the radiation is a solid line or a broken line, it is the same thickness and is drawn all the way to the center, so the density of the line near the center is high, and the line is drawn in black on a white background. appears as a black bulge toward the center, so for patients with astigmatism, the shading of the lines becomes apparent and can be clearly distinguished only in the peripheral areas of the chart.

If the lines are the same thickness and are pointing toward the center, it is not possible to extend the line to the center, so efforts have been made to draw the line as close to the center as possible while leaving the area around the center white.

However, although the difference in shading generally appears in a straight line, it tends to become unclear near the center, and it becomes unclear whether the line that connects it and where is peculiar. .

The Nakajima astigmatism chart using the dotted line has great utility value from the viewpoint of making the characteristics of light and shade obvious.

However, the length of the dashed line and the length of the space (and the pitch)
, and the same thickness was used, so the same drawbacks as mentioned above were suffered.

The purpose of the present invention is to provide a new astigmatism test chart that eliminates the drawbacks of conventional astigmatism test charts. Since it is a broken line, the difference in shading can be recognized more clearly than in the conventional method, so even subjects with a somewhat poor reaction or those with mild astigmatism can easily distinguish the direction of shading.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is a plan view showing the entire astigmatism test chart according to the present invention.
In contrast to the colored number displays 30 arranged at 0 degree intervals (numbers 1 to 12 are colored 180 degrees symmetrically), the central part 11 of the table is a circular blank space, which is traditionally Compared to the table below, it is smaller and more ferocious.

Although the radial dashed lines 20 are spaced at 10 degree intervals in this embodiment, they may be spaced at 15 degree intervals as in the Nakajima astigmatism table described above.

FIG. 2 is an enlarged reference view of the broken line 20, and the trapezoidal blocks 21a''g forming the broken line are black trapezoids with a width of 2 degrees, and each successively moves toward the center with its width T1 length P-
5 and its interval (width of the blank space between blocks) Sl are made small, and the ratio of T:S:P is kept constant, that is, in a similar shape.

Therefore, the closer you get to the center, the smaller T, S, and P become, so the density of lines near the center is the same as the density of the periphery, making it possible to further reduce the blank space in the center, and The inspection sheet is uniform regardless of the ratio of blank areas to lined areas.

Since the present invention has the above-described configuration, when a subject with astigmatism uses the wooden surface as an optotype, lines connecting specific colors and numbers will appear noticeably darker or lighter.

The result of using broken lines is that lines that feel dark are connected and appear close to solid lines, while lines that feel light are clearly distinguishable as broken lines, making the difference clear.

However, with the conventional one, everything near the center looked like a solid line.

On the other hand, the one of the present application faces toward the center while maintaining the clear difference, so reading is easy and reliable.

Therefore, it has the practical effect of being able to obtain test results with relatively high accuracy even when the test subject's response is slow or there is weak astigmatism.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the entire astigmatism test chart according to the present invention, and FIG. 2 is an enlarged reference view of broken lines. 10: Astigmatism test chart, 11: Astigmatism test chart center, 20: Broken line, 21a”g: Trapezoidal block, 30: Colored number display,
T: Width of broken line, S: Spacing between trapezoidal blocks, P: Pitch (
Trapezoid block first child S).

Claims (1)

[Scope of utility model registration request] In a radiation type astigmatism table formed by laying lines radially at equal angles over 360°, the lines are made into broken lines 20, and trapezoidal blocks 21 forming the broken lines are formed in order to taper toward the center 11 of the table. , and are similar in shape, and are characterized by being successively shorter at a constant rate.