A visual aid is any device or equipment that can improve or improve the visual ability of patients with low vision. Similar to hearing AIDS, hearing AIDS can make people with poor hearing hear sounds that they could not hear before, while people with low vision can see things that they could not see or could not see clearly before.
Noun explanation:
Myopia AIDS, also known as magnifying glasses, are used by patients with low vision to observe objects at close range. You should put the object you see on its object distance, and you can see the magnified vertical virtual image of the object, and put it near the apparent distance of the human eye.
It can have many structures, such as: hand-held magnifying glass, which can change the object distance according to the difference of human eyes, making observation more convenient; The frame magnifying glass fixes the object distance, which can free up both hands to work; Magnifier with light source can improve illumination in the dark and enhance brightness and contrast; Glasses-type visual AIDS can choose different varieties according to the different eyesight of human eyes, and the field of vision is larger. The magnification of the near-used visual AIDS is generally 2-6 times.
Refer to the above content: Baidu Encyclopedia-Visual Teaching Aids