by Dan Roberts
with supporting information by
Roy Cole, O.D.
(Updated February 2, 2018)
What is the best kind of lighting for visually-impaired people? Is one kind of lamp better than another? These are two of the most-asked questions in a subject field that can be confusing at best. The bottom line is that people should use the lighting that works well for them.
To help with that decision, here is some basic information about what is available, followed by criteria and recommendations for the safest and best reading/task lamps currently available for individuals with low vision.
Types of Lighting
• Full Spectrum. The closest to actual sunlight, covering the entire range of colors and peaking in the blue light spectrum. Blue light is responsible for glare, and some studies have shown that intense exposure to it may be harmful to the retina over time.
• Incandescent. Most commonly used until around 2010 in the form of a light bulb in table or desk lamps. With a yellowish correlated color temperature (CCT) of about 2800K (Kelvin), this was very safe for the retina. It was not, however, good for contrast, accurate color perception, or economy.
• Tungsten-halogen (or simply “halogen”). A bright “warm white” light (about 3200K), which is good for enhancing contrast. Tungsten lamps are good for use where a lot of light is desired, but the heat intensity of the lamp can be hazardous and uncomfortable when used in task lamps.
• Fluorescent. Bright and economical, this type of lighting is seen most often in public places. Modern fluorescent tube lamps and “compact fluorescents” are usually in the upper “warm white” range (about 4500K), so they are bright and safe for the eyes.
• LED (light emitting diode). Efficient, durable, and small, LED lighting is initially expensive, but much longer lasting and cheaper to run than other light sources. The wider, brighter, and closer the field of light, the more potential risk it carries for the retina. A small array of white LEDs in a task lamp can provide good, safe lighting. In fact, the U.S. Department of Energy states in its 2013 “Optical Safety of LEDs” fact sheet that the proportion of blue emissions by LEDs “is not significantly higher…than it is for any other light source at the same CCT.”
Roy Cole, O.D. (retired director of Vision Program Development, Lighthouse Guild) offers the following suggestions for choosing the best lighting.
For task lighting, the lamp (bulb) should be in an adjustable fixture, and the distance of the light source from the page is as important as wattage. The further away the lamp, the less illumination on the page, and the closer, the more illumination. In fact, if you double the distance, you need a light source 4X as strong to keep the same brightness on the page. Triple the distance, and you will need 9X as strong a bulb, etc. This is referred to as the “inverse distance squared rule.” So adjust the distance of the lamp for optimal visibility.
To reduce the heat of the bulb, use a lamp with an internal reflector (a double shade). This reduces the heat significantly, and allows you to have the lamp closer to the face than you would with a single shade (especially one made of metal).
Here are some other guidelines from Dr. Cole:
If one eye is better and used for reading, position the lamp on that side of the body, slightly to the side. What you don’t want is the light reflecting from the page into your eyes. To check this, turn the light off, place a mirror on the page being read, and see if the lamp appears in the mirror. If it does, re-position it. It should still be close to the page, and to the side of your face, but now perhaps at a slightly greater angle. (Of course, too much of an angle will also reduce the brightness on the page, so you have to find the optimal position for you.) You also want to adjust the light so there are no shadows on the page.
A typoscope is a black card with a slot cut in it to expose the line being read as you move it down the page. This will help to reduce the glare reflecting off the page and improve the apparent contrast of the print.
Glare
Glare from reflective surfaces can be a hindrance for people whose eyes are not capable of modulating light, due to retinal disease. Blue blocking glasses can help by cutting down the haze which surrounds bright objects (caused by blue light waves, which are very short and easily scattered.) Polarized sunglasses will help to reduce glare, especially if the light is reflecting off of a flat surface that is in front of the viewer (eg. a body of water, snow, or a wet road.) The reason for this is that light reflected at a particular angle is “plane polarized” (in the horizontal direction). Polarized lenses transmit light only in the vertical direction, thus removing the reflected horizontal light.
Blue blocking lenses and polarized sunglasses may be purchased commercially, or optometrists can add blue-blocking tint or polarization filters to prescription lenses. Adding tint to prescription glasses can, however, create a safety issue, since the tint will diminish vision in low light. A better option is to wear tinted blue blocking “fit-over” sunglasses that can be removed when not needed.
Suggestions for Better Lighting
Here are some additional suggestions for improving lighting in the home and workplace:
• Place the light directly where you need it. Swivel lamps are preferable, as they can be raised or lowered in order to direct the light.
• Aim the light directly on the task at hand.
• Install dimmer switches for controlling the amount of light in the room.
• Install under-cabinet lighting for tasks in the kitchen or work areas.
• Install extra lighting in places where it may be difficult to move around, such as hallways and stairs.
• Install light switches in accessible locations.
• Install switch plates that are lighted or contrast with wall color.
• Install preset light timers in difficult areas.
• Watch television in a lighted room. It is easier on the eyes. Be sure, however, that the light isn’t placed where it will cause glare or reflection off of the screen. This can be easily checked with the television screen dark.
Recommended Low Vision Reading/Task Lamps
Based upon the above information, here is a list of criteria for choosing the brightest and safest lighting for reading or doing close work.
First, an LED light source is recommended for comfort, safety, and economy. In order of importance, these are the specifications to consider:
- Correlated color temperature (CCT) range of 3000K-4,800K (“warm-to-neutral white”) for eye safety and best contrast
- Color rendering index (CRI) of at least 80 for good color perception.
- Brightness range of 1000-2000 LUX at 12 inches (30 cm)
- Dimmable to alleviate eye strain
- Easily adjustable fixture to prevent glare
- Easy location and operation of fixture controls
- Coverage diameter of at least 12 inches (30 cm) at a distance of 12 inches (30 cm)
- Cost comparable to similar products
- Sturdy construction for safety and durability
- Transparent and educational advertising
After an extensive market survey of low vision task lamps in 2018, the following products have been found to satisfy virtually all of these criteria.
Company: Berryessa Designs
Product Line: Allievo, Elegance, Joseph, Julia*, Elaine*
Models: Desk or Floor*
2018 Cost: $160-$375
Comments: Color Temperature: Warm White (Available in 3400K, 3700K & 4100K)
Company: Dr. Lite
Product Line: Angel Study Light, Clarity Craft Light* with Magnifier, Halo Computer Light*
Models: Desk and 2-in-1 Desk or Floor*
2018 Cost: $240-$300
Comments: Magnifying lens diameter=5” (Clarity only).
Color temperature fixed at brightest and safest level.
Company: Trond
Product Line: TROND
Models: Desk or 2-in-1 Desk or Floor
2018 Cost: $30-$70
Comments: Adjustable color temperature (safest below 5000K)
Company: Sunvalley Brands
Product Line: VAVA
Models: Desk or 2-in-1 Desk or Floor
2018 Cost: $70
Comments: Adjustable color temperature (safest below 5000K)
For more about the science of lighting for low vision, see “Artificial Lighting and the Blue Light Hazard” on this site.