If traditional eyeglasses or contact lenses do not provide enough visual correction for a person to read printed material, he or she or a family member or friend will often purchase a magnifier. However, without a proper clinical low vision eye examination and guidance, few actually get the magnifier best suited to their needs.
In a two-part article, AccessWorld will report on the findings from a study of illuminated magnifiers conducted by AFB TECH in cooperation with the AFB Center on Vision Loss in Dallas. The study incorporates laboratory research and data collected from experts in the field of low vision, along with a survey of seniors with vision loss who use magnifiers. This project is being undertaken to provide relevant information to the increasing number of people with vision loss who are looking to acquire an illuminated magnifier. This information will enable consumers to become much better informed about these devices, and with the assistance of their professional eye care team, to select the magnifier best suited to their vision needs.
This first article in the series discusses the value of a proper clinical low vision examination, as well as several characteristics of illuminated magnifiers and why they are important to take into consideration when selecting an illuminated magnifier.
The Low Vision Examination
Once you have learned you have vision loss that cannot be completely corrected and could interfere with your everyday living, it is of the upmost importance to schedule an appointment with a low vision specialist. A low vision specialist is either an ophthalmologist or optometrist who is trained to conduct a special low vision eye examination.
The low vision examination includes a functional vision assessment to determine how your specific visual impairment affects your ability to perform everyday activities. The low vision specialist will assess your level of vision, prescribe and teach you how to use low vision devices, and recommend helpful services.
This may be a situation in which you need to be proactive. If it is not mentioned to you, ask your eye doctor about a referral to a low vision specialist. The low vision examination is especially important because it is customized to you and addresses your particular life situation. Depending on whether you are in school, in the workforce, or retired, the low vision specialist will work with you to help find ways to accomplish the tasks you need to perform.
In addition, the low vision specialist may recommend specialized reading training. This training can provide useful information and practice that will allow you to read faster and for a longer period. People with age-related macular degeneration (AMD), for example, benefit from eccentric viewing training. This training is important because AMD causes the loss of central vision. Central vision is, as the name suggests, the center of the visual field and normally provides the best ability to read print and see small detail. When this area is damaged, the person will need to use a magnifier to see small details in such tasks as reading or viewing photographs. For the person with AMD, it is important to train another area of the retina to function in place of the lost central vision. This training is called eccentric viewing training.
In combination, magnifiers and eccentric viewing training can greatly improve a person's reading ability and use of magnifiers. There are other conditions that also impair reading ability, and specific training for those types of vision loss can also improve the person's ability to use a magnifier.
Characteristics of Illuminated Magnifiers
The characteristics discussed in this article include the types of illuminated magnifiers, magnification levels, illumination levels, types of light bulbs, light color, battery life, size of the lens, and weight of the magnifier. The following are descriptions of these characteristics and a discussion of why they are important.
Caption: Many sizes and shapes of illuminated magnifiers are available.
Types of Magnifiers
There are two types of illuminated magnifiers: handheld magnifiers, which are lighter and more compact models designed to be held in your hand, and stand magnifiers, which are larger and designed to be placed on a flat surface. Handheld magnifiers offer greater convenience and portability, but often at a cost to illumination and battery life.
Stand magnifiers usually feature an enclosure around the lens and a light source that most handheld magnifiers do not, which has the effect of making the magnified area much brighter. In addition, they usually use larger batteries, and although larger batteries lead to a heavier and bulkier device, they extend the battery life of the magnifier. Stand and handheld magnifiers both have their advantages, and it is important for you and your eye care team to consider which of the two types better suits your needs.
Magnification level
Magnification level is an important characteristic when trying to determine which magnifier is most appropriate for a person's needs. The magnification level is usually stated on the packaging and is an important criterion for many buyers when purchasing a new magnifier. The magnification level can vary greatly among models and generally ranges anywhere from 2x (low) to 14x (high).
When comparing magnifiers, it is important to remember a higher magnification level does not necessarily mean a better magnifier. The ideal magnification is dependent on a person's eye condition. A higher level of magnification will increase the amount by which the magnified text is enlarged, but it also reduces the total amount of text viewable through the magnifier. Thus, the higher the magnification, the smaller the viewable area or field.
Illumination
A major feature of these illuminated magnifiers is their ability to brighten the magnified area via a light bulb built into the magnifiers. This feature can have the effect of increasing the contrast and brightness of the magnified area, making it easier to view, and while all these magnifiers can light up the viewed area, the total level of brightness, or illumination, can differ greatly from magnifier to magnifier. The illumination provided is a measure of the amount of light that passes through the magnifier. This value can range anywhere from 50 candelas per meter squared (low) to 5,000 candelas per meter squared (high).
As with magnification level, it is important to note brighter illumination does not necessarily mean increased readability for everyone. Depending on a person's visual diagnosis, a specific level of illumination may be required.
Caption: A woman uses an illuminated magnifier to read a phone number from the yellow pages of the phone book.
The amount of illumination is not the only relevant quality of the light used in an illuminated magnifier. The type of light bulb and the color of the light also play a role in readability.
Type of Light Bulb
Three types of light bulbs are commonly found in illuminated magnifiers: LED bulbs (a moderately bright, low-power consumption bulb), halogen bulbs (a bright, high-power consumption bulb), and incandescent bulbs (similar to the style of bulbs commonly found in households, but much smaller). The type of light bulb used affects the level of illumination, the color of the light, the amount of heat given off by the bulb, and the battery life.
Most illuminated magnifiers use LEDs, with older models still supporting incandescent bulbs and some of the more expensive magnifiers using halogen bulbs. A 2005 study by Bryan Gerritsen and Robert Christiansen entitled, "Contrast Sensitivity Function Testing and Magnifier Lighting Preference," showed the lower a person's contrast sensitivity, the more likely he or she was to prefer halogen light bulbs, but there were still many people who preferred incandescent or LED bulbs. A drawback of using halogen bulbs is they usually require the magnifier to be plugged into a wall outlet to operate, making it less portable. LED bulbs, while not offering the same level of brightness, require less power to operate than either halogen or incandescent bulbs and can last much longer. So, it is important to realize not one type of bulb is best for everyone. Advice on which type of illumination is best for an individual is another benefit of a low vision evaluation.
Color of Light
The color of light emitted from the magnifier can play an important role in the readability of the magnified area. It is related to the type of light bulb used; LEDs normally give off a bluish light, incandescent bulbs give off a yellowish light, and halogen bulbs give off a yellow-white color. There is no one "best" option when it comes to the color of light, because it depends upon the needs of the specific person. Different people will respond differently to different-colored illumination.
Battery Life
Battery life is an important measurement for illuminated magnifiers for two reasons. It measures how long a magnifier will function before the batteries die and how much illumination is lost when weaker batteries are used. A drop in battery power often leads to a drop in illumination provided by the magnifier, which can result in decreased readability. After a magnifier is used for 24 hours, it is not uncommon for it to lose a third of its battery power and have its illumination drop by more than 50%. This measurement is also related to the type of light bulb being used; for instance, LEDs consume little power and can last for many hours before draining a set of batteries, while incandescent bulbs consume more power and will not last as long. Some magnifiers use AC adapters and need to be plugged into wall outlets to operate, so they cannot be operated by battery power.
Size of the Magnifying Lens
The size of the magnifying lens does not have any effect on its level of magnification, but is still an important measurement. A larger lens will allow you to view a larger area, but can be more difficult to move around the page or take with you. When you purchase a magnifier, it is important to determine the best size for the tasks you want to accomplish. If you plan on reading large documents, a larger lens may be more useful. However, if you need a magnifier only for spot reading, it may be more appropriate to choose a smaller lens. Lens sizes generally range from 1 to 3 inches in diameter for round illuminated magnifiers and 1 inch by 1 inch (small) to 3 inches by 4 inches (large) for rectangular illuminated magnifiers. Higher magnification lenses are usually smaller than low magnification lenses because they have to be much thicker. This makes creating a large high-magnification lens less practical for handheld use because it would be too heavy.
Weight
Weight is another important characteristic of magnifiers, particularly for magnifiers that need to be held above the viewed area. A heavier magnifier can be more difficult to hold or move around a page for extended periods. Even stand magnifiers, which rest on a flat surface, can be difficult to move around the page if they are particularly heavy. Although magnifiers rarely get heavier than 1 pound, this can still be a considerable weight when used often. Handheld magnifiers generally range from 3 to 7 ounces, while stand magnifiers are typically heavier and can range from 6 to 14 ounces.
By explaining the need for a clinical low vision evaluation from a qualified eye care professional and identifying the pertinent characteristics of illuminated magnifiers, we hope to begin building your information base about illuminated magnifiers.
In the next installment of this two-part article, we will discuss AFB TECH's optics lab, measurements we are in the process of taking of popular illuminated magnifiers, as well as the measurement procedures. We will also report on a survey of seniors who use illuminated magnifiers, to add valuable "real-life" perspectives on the benefits and limitations of these useful devices.
Caption: A woman uses an illuminated magnifier to read handouts from a meeting.
