Optical Devices Video
Having trouble with this video? Try one of these:
This is a transcript of a video about optical devices that can be found in the online course Bridging the Gap and in the CareerConnect Virtual Worksites.
Narrator: Optical devices, such as the magnifiers and telescopes shown here, enable people who are visually impaired to magnify images they need to view.
There are many different types of magnifiers available in a variety of sizes, shapes, and magnification powers, and they fall into three broad categories: handheld, free-standing and spectacle-mounted.
As this demonstration shows, users must position handheld magnifiers over viewing material at the distance needed to bring images into focus. Some users find this difficult or fatiguing and fare better with a stand magnifier.
Free-standing magnifiers have a built-in stand that allows users to place the magnifier on top of the viewing material. This avoids the need to hold the device at a specific distance to keep the image in focus.
In the third category, magnifiers are mounted in or onto spectacles, and users such as the one shown here wear them just as they would a regular pair of eyeglasses.
While magnifiers are used for close viewing, telescopes and binoculars are used for intermediate and distance viewing. There are two basic types of telescopes. They can be either handheld or mounted on eyeglasses.
There are three key points to remember about magnifiers and telescopes: The first is that these devices need to be prescribed by a low vision specialist. The second is that as magnification increases, the field of vision decreases. And the third is that higher degrees of magnification often require additional lighting. Let’s look at these points in more detail.
The most important point is that these devices should not be purchased at drug stores and other retail outlets. It’s essential that people who are visually impaired obtain optical devices prescribed by an eye care professional who specializes in low vision or from a clinic that specializes in the evaluation and treatment of their condition. These specialists have a great deal of experience in working with people who are visually impaired and can prescribe the optical devices that will best help the user.
People, who simply go to a drug store, or their regular eye doctor, are often not provided with the most appropriate magnifier or telescope to meet their individual needs. While most eye care specialists are excellent doctors, few have had the opportunity to specialize in working with people with low vision. Conversely, recommendations based on a low vision evaluation carried out by a specialist, will ensure that users select the appropriate devices for completing particular tasks.
The second point to remember is that as the degree of magnification increases, the field of vision decreases. Field of vision is an important consideration. Take reading, for example. High-powered magnifiers will allow users to see only a few letters before having to move the magnifier to the next word. Low vision specialists will help users to achieve the best combination of power and field of vision, depending on what kinds of tasks users wish to accomplish.
For example, a specialist may recommend the use of a handheld magnifier for reading the phone book or price tags in a store. But if users find it difficult or tiring to use a handheld magnifier for extended reading, the specialist may recommend a free-standing magnifier. A specialist may recommend a bar magnifier that allows users to view one line of text at a time, as opposed to a page magnifier that covers a larger area. The power of a page magnifier is low and likely to be of limited assistance to most people who are visually impaired.
Handheld and stand magnifiers range in price from around $5 to $100. Telescopes start at around $50 and can cost up to several thousand dollars when they’re mounted in eyeglasses and designed for an individual’s specific needs.
Some users will choose a combination of optical and non-optical devices in order to achieve the best results and we look at non-optical devices in another of the video segments in this series.