The stereoscopic standards of the comprehensive optometer commonly include two-visual stereoscopic visual mark and four-visual stereoscopic visual mark, both of which are polarization standards. The built-in auxiliary lens of the comprehensive optometer shall be equipped with polarization auxiliary lens during inspection.

Two-visual stereoscopic visual mark

When both eyes look at the same stereo target, the convergence and divergence factors can make the gaze angle of the two eyes' line of sight to the target different, thus forming the binocular spatial image parallax, and the abnormal correspondence of the retina of both eyes caused by parallax is the root of depth perception.

Two-visual stereoscopic visual mark are a pair of lines with the same length vertically above and below, and there is a dot in the center of the upper and lower pairs of lines. After the subject passes through the polarization auxiliary lens, the right eye can see the upper left single line and the lower right single line, and the left eye can see the upper right single line and the lower left single line. During the examination, the subjects were asked to look at the central dot with both eyes at the same time to produce full fusion (as shown in the figure).

Two-visual stereoscopic visual mark

Results of right eye after polarization division

Results of left eye after polarization division

Inspection steps:

1) Complete correction of binocular ametropia

2) Both eyes are equipped with built-in polarization auxiliary lenses. Generally, the right eye is a polarizer with a polarization direction of 135 ° and the left eye is a polarizer with a polarization direction of 45 °

3) Show the two-visual stereoscopic visual mark.

4) Ask the examinee to look at the central dot shaped visual mark with both eyes, and distinguish whether the upper line is concave and the lower line is convex.

As there is a small parallax in the split vision single line visual target image seen by both eyes, there is a scattered parallax in the upper two single line visual targets, which has a tendency of scattered fusion image. With the central dot as the reference plane, the upper visual target is displayed as a concave single line image, and the stereoacuity is about 2.1 '; There is collective parallax between the two lower single line sight marks, with a tendency of collective image fusion. The central circular dot sight mark is used as the reference plane, and the lower sight mark is displayed as a convex single line image, with a stereoscopic acuity of about 1.1 '.

If it is compared with the central round dot visual mark, the lower line is fused into a single linear visual mark but does not show bulge, and the stereoacuity of the subject is greater than 1.1 '; If the upper lines fuse into a single linear visual target image, but do not show depression, the stereoacuity of the subject is > 2.2 '; If there is a delay depression in the upper line for more than 10 seconds during the examination, it shows that the upper part is still a double line visual target image, and the lower part is a convex single line image, suggesting that the subject can not mobilize the divergent fusion image in both eyes, and there is recessive esotropia; If the lower line is delayed for more than 10 seconds, it shows that the lower part is still a double line visual target image, and the upper part is a sunken single line image, indicating that the subject's eyes cannot mobilize collective fusion image, indicating that there is recessive exotropia in both eyes (as shown in the figure).

Results of binocular fusion

Recessive esotropia in both eyes

Recessive exotropia in both eyes