Frisby board stereogram consists of three transparent plastic boards, 1mm, 3mm and 6mm thick respectively. Each board is printed with four pairs of patterns. One of the four pictures prints some of the patterns on the front and some on the back. Because the board has a certain thickness, different parallax will be generated when the eyes observe from different angles, resulting in a three-dimensional sense.

Operation steps:

① It is not necessary to wear bifocal glasses for Frisby plate stereogram examination. Patients with direct naked eyes or refractive errors wear corrective glasses for observation. The examination distance is 40cm.

② During the examination, ask the patient to find out which of the four pictures is different from the other three. Because this examination method has some coincidence, it is necessary to change the orientation during the examination and conduct multiple examinations to ensure that the patient can really see the three-dimensional pattern.

③ Then the different stereoacuity can be calculated by the corresponding plate thickness and inspection distance. The closer the distance, the thicker the plate, the greater the stereoscopic parallax.

④ Starting from the 1mm thick test plate, ask the tested person to point out the stereogram of the four patterns on the test plate. If the tested person's stereoscopic vision function is normal, he can quickly and accurately identify the pattern and tell whether it is convex or concave. If it is impossible to identify, the 3mm to 6mm thick test plate can be replaced until the tested person can quickly and accurately identify or cannot identify.

⑤ Measure the distance between the eye and the test plate, and quantify the stereoacuity through the control table (60 ″ is normal). If the subject can recognize the stereogram in the 1mm thick detection plate within 80cm, the stereoacuity is the highest (15 ″); If the subject recognizes the stereogram in the 6mm thick test plate within 30cm, the stereoacuity is the lowest (500 ″).

Quantitative comparison table of Frisby plate stereogram