RU2055518C1 - Method and device for measuring refraction of eye - Google Patents

Abstract

FIELD: ophthalmology. SUBSTANCE: method is based upon two point light sources, which are disposed at line being perpendicular to main optical axis of eye. Images of light sources are brought into contact onto eye bottom by varying distances between eye and sources. Refraction is determined from the relation given in the description of the invention. Device has two point light sources, which are mounted onto hard base. The device is provided with linear metric scale for measuring and changing distance between the sources. When measuring characteristics of astigmatism, the base is mounted onto rotatable disk, provided with a scale. The scale is calibrated in angular degrees. Axis of the base is perpendicular to the plane of light sources. EFFECT: improved precision. 2 cl, 2 cl, 5 dwg

Description

 The invention relates to medicine, in particular to the determination of clinical eye refraction by the subjective method.

 A known method based on the testimony of a researcher about changes in his visual acuity when selecting corrective lenses using tables C.S. Golovin and D.A. Sivtsev. However, when using this method, sets of optical lenses are required, a special test frame, and a large length of room is necessary. In addition, the determination of eye refraction by this method requires a significant investment of time and is tiring for the subject.

 A known refractometer containing a test object and an optical system consisting of a movable optical component (1) located on the axis of the collimator lens. However, such a refractometer is difficult to manufacture, expensive, and requires the use of sophisticated optics.

 Closest to the claimed is a method for the study of refraction of the eye (2), adopted as a prototype. The method consists in presenting to the patient a test object on the screen in the form of a point luminous spot from a laser beam. The image is focused on the retina using spherical lenses, while physiological astigmatism is diagnosed when the patient perceives the image in the form of a point, and pathological astigmatism in the form of a line. The disadvantages of this method include the use of sets of test optical lenses, the need for complex and expensive optical-electronic equipment.

 The purpose of the invention to exclude the use of sets of optical glasses, complex optical-electronic equipment.

(1) где R рефракция глаза;
l расстояние между источниками света;
L расстояние между источниками света и глазом;
D_зр диаметр зрачка.This goal is achieved using two point light sources, which are placed on a line perpendicular to the main optical axis of the eye, vary the distance between the eye and light sources or between light sources, achieving visual contact of their images on the fundus, and the refraction of the eye is determined by the formula
R

(1) where R is the refraction of the eye;
l distance between light sources;
L is the distance between the light sources and the eye;
D _{sp the} diameter of the pupil.

 The device consists of two point light sources mounted on a rigid base with the ability to move them and a linear metric scale for measuring the distance between the light sources.

 To take a picture of astigmatism, the base is mounted on a rotary disk with an axis perpendicular to the plane of the light sources, with a scale graduated in angular degrees.

The features that distinguish the proposed method from the prototype are:
the use of two point light sources located on a line perpendicular to the main optical axis of the eye;
variation of the distances between the eye and light sources or between light sources until their images in the fundus come into contact;
determination of eye refraction according to the formula (1).

Distinctive features of the proposed device are:
two point light sources with a measuring scale between them;
rotary dial with a scale graduated in angular degrees.

 To prove formula (1), we carry out the following reasoning.

 Consider a parallel beam of light parallel to the main optical axis of the eye. With emmetropia, the focus is on the fundus: with myopia in front of the fundus; with hyperopia after it. Therefore, with any anomalies in the refraction of the eye from a parallel beam of light, a light spot forms on the fundus, the size and shape of which depend on these anomalies.

 However, the subject himself cannot determine the size of the light spot.

 For simplicity of reasoning, we replace the eye with an equivalent circuit and we will consider myopia (the focus is located in front of the fundus) of Fig. 1.

(2) где D_зр диаметр зрачка;
F фокусное расстояние эквивалентной линзы;
d диаметр светового пятна на глазном дне.The distance from the surface of the fundus to the center of the equivalent lens
M

(2) where D _{sp the} diameter of the pupil;
F is the focal length of an equivalent lens;
d diameter of the light spot on the fundus.

 Next, we tilt the parallel light beam at an angle α / 2, which is equivalent to moving a point light source located at a distance L from the eye (L >> M), at a distance l / 2, perpendicular to the main optical axis of the eye, until the light spot is displaced on the fundus at a distance d / 2 (figure 2). After that, “take” one more parallel beam of light and reject it by an angle α / 2, which is equivalent to moving another point light source by l / 2.

(3)
Подставим значение d в (2), получим
M

(4)
Начнем "сдвигать" точечный источник света, находящийся на главной оптической оси, из бесконечности к глазу до тех пор, пока его изображение не совпадет с глазным дном (фиг.3).Two light spots appear on the fundus, in contact with each other. From the likeness of triangles, we find
d R • tgα R •

(3)
We substitute the value of d in (2), we obtain
M

(4)
We begin to "shift" the point source of light located on the main optical axis from infinity to the eye until its image coincides with the fundus (Fig. 3).

(5) где К максимальное расстояние, которое может аккомодировать глаз.According to the lens formula

(5) where K is the maximum distance that the eye can accommodate.

(6)
Величина рефракции, т.о.Substituting in (5) from (4), we obtain

(6)
The amount of refraction, i.e.

(7)
Рассуждения для случая гиперметропии аналогичны и приводят к тому же результату.R

(7)
The arguments for the case of hyperopia are similar and lead to the same result.

 Therefore, by placing two point light sources at a distance L >> of the diameter of the eyeball and shifting (pushing) them until the edges of the light spots touch the subject, we determine the amount of eye refraction by formula (1).

 To take a picture of astigmatism, the light source rotates around the main optical axis of the eye, determining the amount of refraction in various directions.

 Figure 4 shows a device for determining refraction of the eye; figure 4 a device for capturing a picture of astigmatism.

 SMN-9-60-2 1 microlamps mounted on the base body 2 with a slit 3 along which microlamps can move along the guides are used as light sources. A metric scale 4 is applied along the slit, with the help of which the distance between microlamps is measured. To take a picture of astigmatism, the base-case is mounted on a rotary disk 5 with a scale graduated in angular degrees 6. The disk is mounted on a stand with a pointer 7.

 To test the method with these devices, more than 20 patients with various refractive errors were examined in parallel with the generally accepted methodology (the book "Eye diseases" edited by T.I. Eroshevsky and A.A. Bochkareva M. "Medicine", 1977, p. 78-79).

 The accuracy of determining refraction by the proposed method was not inferior to the standard.

 The method and device are simple and cheap and can be widely used for regular monitoring and self-control of people prone to abnormal refraction due to large visual loads.

Claims (3)

1. The method of determining eye refraction, based on the analysis of scattering circles on the fundus from the light source, characterized in that the subject is simultaneously presented with two point sources of light, which are located on a line perpendicular to the main optical axis of the eye, vary the distance between the eye and light sources or between light sources, achieving visual contact of their images on the fundus, and eye refraction is determined by the formula

where R is the refraction of the eye;
l is the distance between the light sources;
L is the distance between the eye and the light source;
D _{z p} - the diameter of the pupil of the subject.  2. A device for determining refraction of the eye, containing a point source of light, characterized in that it is equipped with a second point source of light, while both point sources of light are located on a line perpendicular to the main optical axis of the eye, and mounted on a rigid base with the possibility of their mutual movement along the specified line, and the base is equipped with a linear scale for measuring the distance between light sources.  3. The device according to claim 2, characterized in that the base is mounted on a rotary disk, which is located in a plane perpendicular to the main optical axis of the eye, and is equipped with a scale graduated in angular degrees.

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