Titmus stereoscopic examination chart is the most common measurement method in clinic, which is used to check the near binocular stereopsis of the examinee.

During the examination, the subject must wear matching polarizing glasses to play the role of local binocular vision separation. Generally, the inspection distance is 40cm. After wearing polarizing glasses, the subject forms binocular vision separation, resulting in parallax, and the stereoscopic vision can be known by observing the changes in the graphics.

The Titmus stereoscopic examination chart is divided into three parts. The "fly" chart with a maximum stereoacuity of 3000 ″ is used for qualitative examination of binocular stereopsis to judge whether there is binocular stereopsis function. If there is stereopsis, the fly is obviously floating on the reference plane, and if there is no stereopsis, the fly cannot be detected; Three lines of 400~1000 ″ stereoacuity "small animals" map, each line has 5 "small animals", one of which floats out, and the examinee is asked to point out which animal is raised during the inspection; There are 9 groups of 800~20 ″ diamond "bubble" diagrams of stereoscopic acuity. There are four circles in each group, and one of the four circles is different. After wearing polarized glasses, they are perceived to float due to the parallax of different visual acuity, which is easy for stereopsis to identify.

Operation steps:

① During the examination, the patient shall wear matching polarizing glasses and place the Titmus stereoscopic examination diagram at 40cm in front of his eyes for examination. If the patient has ametropia, they should wear corrective glasses, and then wear polarizing glasses outside the corrective glasses.

② "Fly" diagram is used to judge the presence or absence of binocular stereoacuity. Patients with binocular stereopsis can see that the "fly" is flying through polarizing glasses, because the stereopsis acuity of different parts of the "fly" body in this figure is different, and the wings seen are suspended on the examination book. During the examination, children can grasp the "fly" wings with their hands. The normal reaction should be to grasp on the plane of the chart. If the child grasps on the surface of the chart card, it means that there may be no stereoscopic vision, or the inspection requirements may not be understood and the intention may not be understood.

③ There are three rows of "small animals", i.e. a, B and C. There are five animals in each row, but only one of them has parallax, resulting in a three-dimensional sense. Ask the patient which small animal floats up and ask him to press it down. If the corresponding "small animal" can be pressed and held correctly, it indicates that it has corresponding stereoscopic acuity.

④ "Circle" diagram can accurately determine the stereoacuity of children, which is easy for most patients to understand. The sight mark is divided into nine diamonds, each diamond has four circles, and one of them will feel floating on the card due to the effect of cross parallax. The patient is required to press down the circles floating on the chart card in sequence until the result of two consecutive diamonds is wrong, and the stereoacuity is determined by the last icon judged to be correct.

During the examination, when wearing polarizing glasses and looking at the diamond shaped circle icon, it will be found that the lower circle in the first group is different from the other three circles, with an upward convex three-dimensional feeling. After taking off the polarizing glasses and looking carefully with naked eyes, it is found that the circle below is actually composed of two circles superimposed on the left and right. After wearing the polarizing glasses, the right eye can only see the left circle, and the left eye can only see the right circle. The lines of sight of the two eyes cross in front of the gaze plane, forming a cross parallax. The circle after the fusion of the two eyes forms a floating three-dimensional sense compared with the other three circles; At this time, if the examination chart is rotated 180 ° for inverted examination, the right eye will see the circle on the right and the left eye will see the circle on the left with polarizing glasses. The lines of sight of the two eyes cross behind the gaze plane, but do not cross in front of the gaze plane, forming a non crossing parallax. At this time, the binocular observation will find that the fused circle has a sinking three-dimensional sense relative to the other three circles; If the examination chart is rotated 90 ° and placed vertically for observation, the vertical parallax is formed because the circles seen by the left and right eyes are in the vertical position, but the stereoscopic sense disappears. Therefore, the vertical parallax cannot form stereoscopic vision, the horizontal parallax can form stereoscopic vision, the horizontal poor parallax can form the stereoscopic sense of the object moving near, and the horizontal non cross parallax can form the stereoscopic sense of the object moving far.