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Once upon a time, tints were easy. The lens material was glass and the choices were pretty basic…
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Clear
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Pink
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Yellow
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Green
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Grey
Clear for everyday use and of course for night driving. Pink if you worked in an office with fluorescent lighting or for post-cataract eyeglasses. Yellow for the sportsman. Green or grey for your sunglasses, if you wore them. Life was simple.
And then the Pittsburgh Plate Glass Co. gave us CR-39 (Columbia Resin 39).
I like to think that Sunshine Somebodyorother was tie-dying some t-shirts when her brand-new, lightweight plastic lenses fell out of their frame into the dye and voila! Custom tinted lenses were born! We could literally look at the world through rose-colored glasses, or purple-tinted lenses in a round metal frame, a la John and Yoko. Our Mothers were coming home from the Opticians with “blue on the top and pink on the bottom” cool new lenses. Life just got a little less simple, at least optical life got a little less simple.
The tint you can’t see for the light you can’t see
Ultraviolet light is not a good thing for eyes and skin. It makes things deteriorate, or degenerate as in age-related maculopathy (ARM) or macular degeneration. It can make things grow, like cataracts, pterygium or pinguecula. All eyes should be protected from UV damage, even patients with UV-absorbing lens implants. That’s right! Grandma needs sunglasses too!
Certain medications can make us more susceptible to UV damage, including sulfanomides, tetracyclines, diuretics, tranquilizers and oral contraceptives. Although the questions are sensitive, we need to know about these things when we’re designing the perfect lenses for our patients.
If you can’t see the tint, how do you know it’s there? Simply cover a plastic photochromic lens with the lens in question and expose it to sunlight. If the photochromic lens darkens, there’s not enough UV protection on or in the lens. Use the same test to prove to your patients that cheaply made sunglasses may look good, but can be bad news for their eyes.
UV Index
(US Weather Service, Environmental Protection Agency, World Health Organization) |
Exposure Level
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0 1 2 |
Low |
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3 4 5 |
Moderate |
| 6 7 |
High |
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8 9 10 |
Very High |
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11 and greater |
Extreme |
Choose the right tint for the right use
Pink was once the color of choice for post-cataract glasses and for office workers sensitive to fluorescent lighting. It does not affect the colors seen through it. Currently, pink (rose, flesh) tones are popular for cosmetic tints while the preferred treatment for glare control is the application of an anti-reflective coating.
Yellow is arguably the most controversial of tints. Many long-distance drivers swear by their yellow tinted lenses for comfort and increased visibility at night. However there are no definitive studies that draw that conclusion. Most studies report that there is no increase in visual acuity through yellow lenses, in fact visual performance is slightly worse than through no filter at all.
In certain circumstances, a yellow lens can darken a bright blue sky therefore increasing the contrast and making some things easier to see, like perhaps your golf ball in the deep rough.
A tinted lens of any color, yellow or otherwise is never recommended for night driving. The reduction in visual acuity (20/20 to 20/32) in dim light is significant enough without further reducing acuity (20/46 behind a tinted windshield at night) by adding even a slight tint (20/46 to 20/60 at night behind a tinted windshield with an 18% tint).
Green lenses transmit light on a curve that is very nearly the same as the color sensitivity of the eye. For many years it was the color of choice for sunglasses, beginning with sunglasses made for the military. Green tinted glass lenses demonstrate good absorption for both UV and IR rays.
Gray, or Grey if you’re British, is the most popular color tint for sunglasses. It does not distort the colors seen through it and is considered a neutral color. It is also the preferred color for people with red-green color deficiencies, since the ANSI requirements for sunglass and cosmetic tints are related to traffic-signal recognition.
Interestingly, brown and yellow lenses do not meet the ANSI standards for non-prescription sunglass lenses, but are readily available in prescription lenses. A normal person will not be troubled by those colors, but a color defective person (red-green color deficiency) would not be able to correctly identify traffic signals. That’s another piece of valuable information, like medications, that you should get from your patients.
Brown is a very popular sunglass tint in Europe. Brown tints share some of the same qualities as yellow tints, in that it reduces the transmission of blue light and enhances contrast on bright or hazy days.
Interestingly, the majority of “sport-specific” lens tints fall into the yellow-orange-brown family of colors, some polarized, some not. These particular families of colors filter blue light to enhance acuity and contrast. All are either polycarbonate or other mid- to high-index materials for safety.
Is it me, or do all those sport-specific tints have odd names? Some days, I miss Gray 88 or G-15.
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Primary Function and Shade |
Light Transmittance |
A cosmetic lens or shield (light)
More fashion than function |
Transmission of greater than 40% |
A general purpose lens or shield
Normal sunglasses |
Transmission of between 8% and 40% |
A special purpose lens or shield (very dark)
Very intense light |
Transmission between 3% and 8% |
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A special purpose lens or shield (strongly colored) Filters specific spectral colors |
3% minimum transmission |
--from ANSI Z80.3-2001
To polarize or not to polarize, that is the (heated) question
For the vast majority of wearers, polarized lenses are the best sun/glare protection available. They reduce fatigue while driving, reduce glare from water and snow or ice and they block UV. However, there are situations where polarized lenses can create hazardous situations.
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Some wearers may be sensitive to the stress patterns on car windshields. Polarized lenses may enhance those patterns, which are similar to the “cross” patterns seen on tempered glass lenses when viewed through a polariscope.
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Skiers who turn and lean may find that their ability to judge the constantly changing surface of the snow. Think black diamond, trees and ice patches at speeds topping 100mph.
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Golfers may find it difficult to judge the condition of a course. That’s probably why pro golfers seem to be wearing their sunglasses on the backs of their hats.
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Cars with LCD instrumentation. Polarized lenses may cause the display to disappear.
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Pilots may encounter several different problems with polarized lenses:
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Polycarbonate windshields may display distracting stress patterns
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Some cockpits may have polarized displays which may disappear with polarized lenses.
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Horizontally reflected light from oncoming aircraft is eliminated and the aircraft may not be seen as soon as it should be.
So polarized lenses are the best sunglasses for glare reduction and comfort, except when they’re not.
Finally, tints can be fun and they can be necessary. The key to helping our patients decide which lens, lens tint and/or lens treatment is to ask the right questions including medications, hobbies, occupation and driving habits. Our function as eyecare professionals is to know which combination of material, style, tint and treatment will satisfy those requirements. Oh, and by the way, tint samples fade with time so keep yours current to avoid promising one color and getting a slightly different one from your lab. If you do your own tinting in-house, that stuff doesn’t last forever. Change your tints regularly and keep a close eye on the temperatures in you tint unit.
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