SU41636A1 - Instrument for the examination of visual acuity - Google Patents

Description

When studying changes in the functional activity of the eye and its influence under the influence of work (visual fatigue), as well as in evaluating the effectiveness of measures to combat eye fatigue and improve vision conditions, one of the main methods is to study visual acuity.

However, the methods of measurement commonly used for this purpose with the help of a table of letters, viewed from different angles of view, are not sensitive enough; They allow us to investigate the sharpness of vision only statically, without taking into account changes in time, and, moving from one row of letters to another, we have a change in angular size by 0.1, while under the influence of work there come more subtle abnormalities that require gradations About 0.01.

The solution of this problem is feasible using the proposed device.

On the proposed drawing shows schematically a General view of the proposed device in a partial vertical-median section.

The proposed device consists of two chambers, blackened from the inside. In small

(U

Chamber 2 is placed an electric lamp with a point body glowing. The light rays are collected using a lens system 4, after which they exit through the diaphragm 5 into the large chamber 1, where a displacer is installed in their path; a screen 6 of transparent glass, on which a Landoldt ring 7 of copper foil is glued. Due to such a device, the image of the ring is projected on the screen 8 of milk glass. The distance between the two screens can be adjusted using the rack 9, which allows the size of the ring projected on the glass 8 to be resized. Rotation of the lever 10 allows you to change the direction of the rupture of the ring. The double aisle 11, placed outside the chamber 1, gives readings characterizing the dimensions of the projected ring, calculated for visual acuity: the upper scale when testing the sight at a distance of 5 m (with accommodation off) to a lower distance of 30 cm (with accommodation on). The scale is illuminated by the same light source by directing a portion of the rays through an articulated tube 12 provided with an optical system.

I 10

The subject invention.

1. A device for examining visual acuity, consisting of two cameras, in one naz of which a light source with a lens system and a diaphragm is installed, characterized in that, to investigate visual acuity, in the path of the rays, the second

The camera 1 is equipped with a transparent screen movable by means of a knob 9 with a Landoldt ring 7 glued on it, the image of which is projected on the screen 8 made of milk glass. 2. The form of execution of the device indicated in Clause 1, characterized in that lever 10 is used to change the direction of the ring.