What Are Low Vision Optical Devices?
Low vision optical devices, such as magnifying reading glasses, magnifiers, and small telescopes, are different from regular glasses and magnifiers.
Since low vision optical devices are task-specific, your doctor may prescribe different devices for different tasks. One device can be used for reading the newspaper, another for watching TV, another for spotting bus numbers or street signs, and still another for watching a football game or a play.
Some doctors recommend starting with one device to see how you manage, and adding additional devices as you become used to working with the device you have. It is extremely helpful to both you and your doctor if you can make a list of the tasks or activities that are most important to you and share that information with him or her.
The low vision service is incomplete unless you've been taught how to use the devices that have been prescribed for you. After you've been prescribed a low vision device, such as a magnifier, it's important to learn how to use it when you get home.
Low vision optical devices can be grouped into two basic categories:
- "Near" optical devices for activities such as reading, sewing, writing, and crafting
- "Distance" optical devices for activities such as attending movies and sporting events; reading street signs and price tags; and identifying numbers on buses and trains.
"Near" Optical Devices
"Near" devices are for close work, such as reading and sewing. The most common devices in this category include:
The simplest device for reading is the stand magnifier. When placed on the page, this type of magnifier is automatically in focus for reading.
The advantages of stand magnifiers are:
- They are inexpensive and readily available
- The focusing distance is set by simply placing the magnifier on the page
- They are helpful for individuals with poor motor control
- They can be used in combination with regular eyeglasses.
- Some stand magnifiers come with built-in lights.
The disadvantages of stand magnifiers are:
- Book bindings may present a problem, as the magnifier may not remain in a stable or fixed position
- They can block the reading light and reduce the amount of illumination that reaches the page.
- They can be bulky and are not as portable as smaller hand-held magnifiers.
The hand-held magnifier is especially useful for shorter-term "spot" and single-word reading, such as looking up numbers in the telephone book or reading price tags.
The advantages of hand-held magnifiers are:
- They are usually inexpensive, portable, and readily available.
- They have the most "normal"appearance of any low vision optical device.
- They are available in a variety of shapes, sizes, and magnification strengths.
- You can vary the distance at which you hold the magnifier from your eyes, depending upon your lighting and reading needs.
- Some hand-held magnifiers come with built-in lights.
The disadvantages of hand-held magnifiers are:
- They require steady hands and good motor control.
- Higher power (or stronger) magnifiers allow you to read only a few letters at a time.
- Your reading speed will likely decrease.
- Stand magnifiers without built-in lights require supplemental lighting for best vision.
- Finding and maintaining the correct focus is sometimes difficult.
Magnifying Reading Glasses
Magnifying reading glasses allow an individual to read for longer periods of time. They are also called "microscopes" because they produce magnified images of small words and objects.
The advantages of magnifying reading glasses are:
- You can read several words at one time.
- You can read with both eyes if your prescription is a lower-powered one.
- You can read for longer periods of time than with hand-held and stand magnifiers.
- Both hands can be kept free while reading.
- You are probably familiar with reading glasses already.
The disadvantages of magnifying reading glasses are:
- A higher magnification power can require a very close reading distance, which can be tiring and frustrating for some individuals.
- Training is usually required to use magnifying reading glasses effectively.
- Finding and maintaining the correct focus can be difficult and require practice and experimentation.
- Your neck, arm and shoulder muscles can become fatigued if you read for longer periods of time.
- It's possible to experience eyestrain and headaches initially.
- It's important to experiment with selecting and positioning appropriate lighting.
Distance Optical Devices
"Distance" devices are best for activities such as television viewing, a visit to the movies/theater, attending a sporting event, and bird watching.
The most common type of distance optical device is the hand-held telescope, also called a "monocular" because it is used with one eye and has a single eyepiece.
The advantages of hand-held telescopes are:
- They are inexpensive, small, and portable.
- Thay are available in a range of magnification powers.
The disadvantages of hand-held telescopes are:
- They provide a very limited field of view and are best for "spot" viewing, such as reading street signs.
- Walking or moving about while looking through the telescope is not recommended because depth perception and balance are affected.
- They require steady hands and good motor control in order to focus the lens.
- Even slight hand movements or tremors can affect the clearness of the image.
Note: Monocular telescopes also come in clip-on versions that attach to eyeglass frames and leave both hands free.
Spectacle-mounted telescopes are permanently attached to the lens of your eyeglasses.
The advantages of spectacle-mounted telescopes are:
- They can be monocular (for one eye) or binocular (for both eyes).
- They leave both hands free and are more stable than hand-held telescopes.
- They are available in a range of magnification powers.
The disadvantages of spectacle-mounted telescopes are:
- They are the least "normal" looking of any low vision device.
- Walking or moving about while looking through the telescope(s) is not recommended because depth perception is distorted and balance is affected.
Bioptic telescopes are mounted on the upper part of each eyeglass lens. This placement allows the user to look through the bottom half of the lens while walking and then stop and look through the telescopes to read a sign or identify a person. In some states, under strictly specified conditions, bioptic telescopes can be used while driving.
Telemicroscopes have an extra removable lens cap that fits over the end of the telescope and allows the user to focus closer for reading or other near tasks.
The telemicroscope, in contrast to magnifying reading glasses, allows users to work at a more "normal" or "arm's length" working distance, which is also helpful when playing card games, knitting, or using the computer.
It's important to remember that the benefits of optical devices can be enhanced by combining them with non-optical devices (such as lighting), to increase illumination and contrast and reduce glare.
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