Visual impairment which cannot be rectified in spite of medical and surgical operations and glasses or contact lenses is called insufficient vision. Although it is mostly accepted as visual acuity, in fact loss of contrast, ability of accommodation to light sensitivity or seeing objects as deformed can be included in this group.

Visual impairment can be congenital or occur due to an accident, aging, or a disease complication. It is for certain that this condition will cause a psychological breakdown in the individual. Particularly in slowly progressing cases, individuals experience a decrease in the quality of their daily and working lives. Apart from rehabilitating vision, individuals should be provided with psychological support.

Figure 1. Telescopic spectacles (left) and retinal prosthesis (right).

Although it is slight, people with visual impairment have the ability to see. These people complain about seeing the environment behind a smoke screen or matte glass. This vision does not fulfill the daily needs of these individuals. It may be possible to bring the impaired vision to the normal visual level by increasing it by various techniques and devices.

There are a number of auxiliary devices developed for people with visual impairment. A single device that converts vision to normal is not always the case. The devices must be tested by expert teams and then recommended to the people in need. Auxiliary devices for people with visual impairment can be divided into two groups: optical and non-optical ones.

The most typical example of optical devices is magnifying glasses. They are more powerful than normal glasses. When using them, the writing to be read should be taken quite close to the eye, otherwise the writing stays out of the focal point. This condition may first scare the person, but it is overcome in time. Magnifying glasses can be mounted directly to the glasses or added to the diopter value of the individual. These glasses have aspheric and telescopic types. The telescopic type has a coarser appearance but provides vision from a longer distance. The aspheric type seems more aesthetic but has a narrower field from a shorter distance. Another example of optical devices is magnifiers. They consist of two types: hand-type and desk-type. Some patients also get help from telescopes when they watch television or look at billboards in the open-air. Furthermore, a closed-circuit television system has been developed to help people with visual impairment. These reflect a magnified image of the material to be read into a television screen. The magnification rate and contrast can be adjusted and are easier to use than other devices. They are only used to read and look at the pictures.

Non-optical devices are products designed for people with visual impairment. For example, large-print newspapers, telephones with large keys, and high-contrast watch screens are included in this group. Some of these can be imported from abroad.