Any device that can help the patients with low vision to read and see is called a visual aid. Low vision aids can enable visually impaired people to see clearly what they could not see, which greatly improves the quality of life, study, and work of visually impaired patients, making them more confident and independent.
Optical Vision Aids
Optical vision aids are devices that can improve the level of visual activity with the help of optical performance. It can be a convex lens, a concave lens, a triangular prism, a flat mirror, or an electronic device. The lens can change the size of the target, and the degree of change depends on the refractive power of the lens; a triangular prism or a flat mirror can change the imaging position of the target on the retina.
There are many types of optical vision aids, such as those for distance use, eyeglass telescopes, monoculars, finger ring telescopes, etc., and those for near-use, such as glasses magnifiers, handheld magnifiers, and stand magnifiers. Various types of optical vision aids have their own advantages and disadvantages, and should be selected according to the practical principles of low vision patients.
How to choose the right optical vision aids?
1. The larger the magnification, the stronger the magnification ability, but it also makes the use more difficult. When matching glasses, it should be based on the conditions that can meet its needs, and try to choose the smaller magnification.
2. The shorter the working distance, that is, the closer the lens is to the eye, the larger the field of view and the larger the observation range. But the actual optimal distance depends on the distance at which the patient is most comfortable when reading.
3.The heavier the aid, the more inconvenient it is. Patients often use visual aids to read for a long time, so vision aids should not be too heavy. Plastic lenses are lighter than glass lenses, but their surfaces are easily scratched.
Non-optical Vision Aids
Non-optical vision aids do not use the magnifying effect of the optical system, but various devices that enhance visual functions by improving the surrounding environment. They can be used alone or in combination with various optical vision aids. Such as enlarged prints, high-intensity illuminators, guide dogs, white cane, and high-contrast objects, etc.
1. In many cases, people with low vision can get more help with non-optical vision aids.
2. The use of amplified materials does not require much high technology and cost, but it is very practical.
3. The larger the font size, the lower the reading efficiency. The font size is based on the principle that low-vision users can see clearly.
Electronic Visual Aids
Electronic visual aid is an electronic graphic magnification device, which transmits the read documents, pictures, observed objects, etc. through the photographic lens and sends the image to the screen for users to read. Users can adjust the size, contrast, brightness, and even the color of the projected image on the screen according to the degree of personal vision. Electronic vision aids are high-tech products that integrate professional technologies such as optics, ophthalmology, electronics, mechanics and ergonomics.
1. The magnification can be adjusted (4X ～ 60X magnification).
2. Reading distance has greater variability.
3. The brightness and contrast can be adjusted.
4. Improve the durability and efficiency of user reading.
5. Some CCTV vision aids are bulky and are not conducive to carry and transport.
Vision aid is only an auxiliary tool that can help patients with low vision, nothing more, it will not have any therapeutic effect, nor will it improve the vision itself, of course, it will not cause its own vision to deteriorate. Users can choose the right vision aids based on their needs.