WHAT IS THE RIGHT MAGNIFIER ?
On selecting a magnifier, it is a good idea to begin with identifying the exact purpose for its use (e.g., reading the newspaper, reading medicine labels, or watching television). Once you have specified the task, categorize the undertaking based on two criteria: the duration of viewing and, the distance of viewing. Distance and duration are the two device criteria, more than anything else, that determine the task appropriateness of a given magnifier design.
Distance refers to the space between the viewer and the object that is to be seen. This distance bears dramatically on the type of magnifier design required. Distance is categorized as follows:
Near tasks – usually engaged in at a “reading” distance (usually 50cm or closer), these tasks include reading, writing, eating, etc.
Intermediate tasks – usually engaged in at about arm’s length 50cm – to 100cm) these tasks can include viewing a computer monitor, reading sheet music, playing cards and other hobbies and handicrafts.
Distance tasks – any visual task that is not near or intermediate (usually 6′ or more). These tasks are dominated by watching television, reading indoor and outdoor signs, watching sporting events, etc.
This refers to the time period for which you will be using a given device to accomplish a given task. In low vision, it is simplest to think of tasks as follows:
Short-term spotting tasks – engaged in for a maximum of only a few minutes at a time, these tasks include reading menus, reading price tags, writing return addresses on envelopes, reading street signs, etc.
Extended viewing tasks – engaged in for a longer period of time, these include reading books, newspapers or magazines, watching television, writing letters, etc.
The grid table graphically depicts the relationship between the Distance and Duration of the visual task desired and the design category of magnifying devices best suited.
Distance and duration identify the visual goal and will quickly narrow the range of devices most appropriately suited. The magnifying power required, as well as the need, or desire for illumination, will then further pinpoint the range of options.