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.

Four-visual stereoscopic visual mark

The principle of four-visual stereoscopic visual mark inspection is the same as that of two-visual stereoscopic visual mark. After binocular polarization separation, multiple sight marks are used to quantitatively simulate collective parallax, so as to quantitatively analyze the lowest binocular parallax that can induce stereovision.

Four-visual stereoscopic visual mark is a linear sight mark with the same length in the upper, right, lower and left directions, and the spacing of each group of lines increases in turn according to the upper, right, lower and left directions, which is called the inspection group sight mark. There is a circular dot shaped sight mark in the center, and the plus sign, five pointed star, square and triangle sight marks are respectively set in the upper, right, lower and left directions, which are called reference group sight marks. After the examinee passed through the polarization auxiliary lens, the four sight marks seen by the left and right eyes were divided from the upper, right, lower and left pairs of double lines, and the double lines seen by the left and right eyes were single lines with slight differences in position (as shown in the figure).

Four-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 four-visual stereoscopic visual mark.

4) Ask the subject to look at the reference group's visual targets with both eyes, and distinguish whether the upper, right, lower and left detection visual targets are fused into single linear visual targets (as shown in the figure), and whether they are convex compared with the reference group's visual targets.

At the time of detection, the set parallax of each component visual target image seen by both eyes occurs. The four sets of binocular visual targets form a single line image with four bulges. The greater the set parallax is, the greater the bulge is. The bulge increases in order of up, right, down and left.

Compared with the reference group, if the four groups of double line vision markers all form four convex single line images, the stereoacuity of both eyes of the subject is ≤ 1 '; If the upper lines fuse into a single linear visual target image, but do not show bulge, the stereoacuity of both eyes of the subject is greater than 1 '; If the upper line and the right line merge into a single linear visual target image, but do not show bulge, the stereoacuity of both eyes of the subject is greater than 2 '; If the upper, right and lower lines are fused into a single linear visual target image, but do not show bulge, the stereoacuity of both eyes of the subject is greater than 5 '; If the four groups of double line visual targets are fused into single line visual target images, and no bulge is displayed, the stereoacuity of both eyes of the subject is greater than 10 '.