Prepared By: Mary N. Harrison, Professor, Consumer Education

Choosing Sunglasses

Teacher’s Guide

Prepared by: Mary N. Harrison, Professor, Consumer Education

University of Florida

Situation:

Sunglasses are an important consideration for those living in the Sunshine State. Days are long and the sun is bright. For people who spend time outdoors, particularly around water and sand, sunglasses are a must. Many drivers depend on sunglasses to overcome the glare from the highway and other surroundings.

In the 1920s, military aviators donned green-tinted glasses to cope with high altitude glare. At first the idea caught on slowly, but soon it accelerated, and now most people are aware of the need for sunglasses.

Sunglasses are now considered a fashion item as well as a functional one. Advertisers equate the use of sunglasses with glamour. High priced sunglasses carry the name of prestigious fashion designers. For example: which are you more likely to find in the stores, sunglasses by Liz Claiborne or the Mayo Clinic?

As the public becomes better informed about the long term effects of over exposure to sunshine, emphasis is being placed on the use of sunglasses. Some sunglasses claim to protect the user from ultraviolet light. Others claim to block the blue segment of visible light, invisible infrared rays or a combination of these.

Sunlight and Vision

Sunlight contains light-rays of varying wavelengths known as UV rays. Some of these are visible to the eye as light while others are invisible. Wavelengths are measured in nanometers (billionths of a meter). The shortest wavelengths are believed to be the most dangerous. Studies indicate ultraviolet light does the most damage to the eye. The shortest wavelengths (called UVB) are believed to be the most dangerous. Although the longer wavelengths of the UV band (called UVA) can do damage, they do less detrimental harm than the UVB rays.

The human eye has a transparent covering over the iris (colored part of the eye) and pupil (dark center of the eye). This covering is called the cornea. The cornea absorbs the UV rays. It is susceptible to damage from UVB and especially from wavelengths shorter than 295 nanometers.

The cornea, under normal conditions, can repair damage to itself from UV. However, when subjected to prolonged exposure under bright conditions, it can’t adequately protect itself, and recent studies indicate the lens can be damaged. This can result in some types of cataracts (clouding of lens that interferes with vision).

The lens acts as a filter absorbing the UVA and any UVB not blocked by the cornea. It protects the light sensitive retina at the back of the eye. Some medical authorities believe that exposure to bright light over many years may age the retina and contribute to the development of macular degeneration, a disease that causes blindness in older people.

Unfortunately, eyes exposed long-term to the sun’s rays may not be able to recover. Although these vision problems may become evident in later life, the damage that causes this problem starts early in life. You get most of your lifetime exposure to UV rays before age 25.

Spending a few hours in bright sunlight can delay the eyes' ability to adapt quickly to nighttime or indoor light levels. This can make driving at night after spending a day in the sun more hazardous. The sun's brightness and glare interfere with comfortable vision and the ability to see clearly by causing squinting and watering of the eyes. Wide-brimmed hats and caps can block about 50% of UV radiation from the eyes, but eye doctors say that is not enough protection.

Objectives

Program participants will:

• Learn the importance of using sunglasses.
• Learn the types of sunglasses and how they relate to individual needs.
• Learn to determine the quality indicators in a pair of sunglasses.
• Select well constructed and distortion free sunglasses for personal use.
• Compare quality and cost and will select good quality for a reasonable price.

Concepts To Teach

Sunglasses are treated with a chemical to absorb UV rays. Tests on sunglasses indicate that any sunglasses that blocked 75% of the visible light reduce the UV adequately for most people. Sunglasses range all the way from very inexpensive to designer glasses that cost hundreds of dollars. Most of the glasses sold today will give adequate protection from UV radiation. However, there are differences in the quality of frames, workmanship, and type and color of lens.

Standards

In 1986, the American National Standards Institute developed voluntary standards for manufacturers of nonprescription sunglasses, which are divided into three types: cosmetic, general-purpose, and special purpose. The standards included limits on the transmission of UVB and UVA. They are:

• Cosmetic glasses must block at least 70% of the UVB.
• General purpose must block 95% of the UVB and most (60%) UVA.
• Special purpose must block 99% of the UVB and most UVA. (For skiing, mountain climbing, white beaches and bright sun, other outdoor sports and people taking certain medications).

The American Optometric Association, the American Academy of Ophthalmology and Prevent Blindness America recommend that sunglasses block 99% to 100% of UV radiation. The label should read either UV 400 or 100% UV protection.

Type of Lens

Most sunglasses manufactured today have plastic lens. This enables the lens to be light in weight, tough in strength and resistant to breakage. Most plastic lens has the color added as an ingredient of the plastic. When color is added as a coating, scratches can ruin the finish. There are six general types of sunglass lenses:

Plain lens

• These sunglasses are tinted with color spread evenly over the entire lens. They come in several different colors. Any of the colors will block out the invisible UV rays. However, the color of the lens will affect the color of what you see. Neutral grey and sage green have the least change in colors. The darker the tint the more visible sunlight will be blocked out. Most of these sunglasses screen out from 60 to 97 % of the sunlight.

Gradient lens

• Gradient lens can be either single or double gradient, though most are single. A single gradient lens is darker at the top than at the bottom. They are good for a car trip because they cut light from the road and sky but let you see what is going on in the car. They are bad for the beach where light bounces off sand and hits the glasses from below.

Polarized lens

• These lenses are made by placing a layer of polarizing material between two layers of glass or plastic. They do an excellent job of blocking reflections and glare from flat surfaces such as water and pavement at certain angles. They can provide added comfort and better vision for those who do a lot of driving or boating. For certain sports such as golf, polarization has the potential to cause a loss of visual information that may reduce performance. Polarization may not be the best choice for all situations, and should not be used for certain activities such as piloting an airplane. They can be handy in allowing fishermen to see deeper into the water.

Photochromic lens

• Photochromatic lenses are an ideal choice for those not wanting to carry a separate pair of sunglasses along with their regular eyeglasses. These lenses are made of light-sensitive material that automatically darkens when exposed to outdoor sunlight and lightens in indoor light. Step outside and they darken in about 30 seconds. Step inside and they lighten in about 5 minutes. They tend to darken more in cold weather than hot. Also, car windshields interfere with the darkening process, making photochromic lenses less effective for driving.

Polycarbonate lenses

• Polycarbonate lenses are a must for sunglasses worn for sports and activities that are potentially hazardous at work and around the home. These lenses provide excellent impact protection, but are not a substitute for occupational or sports safety eyewear. Polycarbonate lenses are especially tough but scratch easily. Be sure to look for ones with scratch-resistant coatings.

Mirrored or flash lens

• “Flash” is a colored mirror-like finish on lens. These shades don’t perform any better than regular ones. They reflect some of the light rather than absorbing it like most sunglasses. These lenses are easily scratched, so if you like them, look for ones with a scratch-resistant coating - and take good care of them.

Sunglass Lens Tints

Colors added to sunglass lens help absorb light as it passes through them. There are several different colors of lens tints to choose from. Your choice of color may depend on a combination of personal taste, style and purpose, but there are a few important color-related benefits to consider.

For general use, the colors green, grey, yellow, or brown are recommended in order to minimize color distortion.

Gray is a popular choice as it allows us to recognize and perceive colors more naturally and reduces brightness.

Brown and amber tints reduce glare, including the glare created by the blue frequency in sunlight, which can make things appear hazy. Brown and amber tints distort colors more than gray tints do. Brown and green lenses tend to enhance contrast.

Yellow tints reduce the haze from blue light better than browns, so they really sharpen up the view. Orange and yellow lenses have excellent contrast enhancement and depth perception, but tend to distort colors. Yellow lenses tend to be a favorite choice of golfers and shooters.

Green tinted lenses reduce glare and help filter out some of the blue light. They provide good contrast between objects.

Rose colored lenses might be a good choice if you participate in water sports or other outdoor activities, because they provide good contrast for objects viewed against blue or green backgrounds. Red lenses cause significant color distortion but are good for low-light conditions.

Blue or purple lenses are chosen mainly for style and fashion purposes, as they offer no real benefits to vision.

Cost of Sunglasses

Price is not a gauge of UV ray protection or of lens quality. Sunglasses range in cost from low cost to expensive. Designer glasses are usually among the most expensive. Studies have found that some higher-priced sunglasses have poor quality lenses or inadequate UV ray protection, while some relatively inexpensive sunglasses are quite good in both categories. Almost all protect your eyes from UV ray radiation.

Some sunglasses may not have sturdy frames or lenses that are securely fastened into the frame. However, you can buy a well made pair of sunglasses for a modest price. Price may influence construction but it is not an assurance of quality. There are variations in the quality of sunglasses in all price levels. A recent study by an independent consumer testing agency found that all of the glasses that it tested, screened out 70% or more of UVB rays. That is enough to make them adequate for most people.

Since sunglasses are considered to be a “medical device” they are regulated by the Food and Drug Administration (FDA). A regulation requires they be “impact resistant” and safe. Thus, they don’t break or shatter easily and are safe to use.

Most young people buy inexpensive sunglasses for several reasons. They do not take very good care of them, thus the glasses need to be replaced often when lost, scratched or bent out of shape.

Some people who wear eye glasses, purchase sunglasses made to their prescription. These are somewhat expensive and should be handled with care. Others buy “clip on” sunglasses that can be attached to their eye glasses.

Sunglass Labels

There is no uniform labeling of sunglasses with regard to UV ray protection. Unfortunately, labeling is not required, so many sunglasses do not carry a label other than country of origin (where they are made). There are almost as many UV labels as there are sunglass manufacturers and studies have found many of the labels are misleading. Many optical offices have an instrument that can measure the amount of UV blocked, so if you are concerned about a particular pair of sunglasses, this may be a viable option.

Some glasses are labeled with useful information such as “meets ANSIZ80.3 General Purpose UV Requirements.” Glasses meeting these standards, block out 95% of UVB and 60% of UVA. Those labeled “Cosmetic UV Requirements” do not block out as much UV radiation. They do block out 70% of the UVB rays.

Anyone taking photosensitizing medications, (medications that make you sensitive to the sun) should select sunglasses labeled ANSI 80.3 Special Purpose UV Requirements. They block out 99% of UVB and most of the UVA rays. For the best protection from UV rays, the label should read either UV 400 or 100% UV protection.

Buying Sunglasses

Buying sunglasses can be complicated. There are currently no federal sunglass requirements regarding UV protection, light transmission levels or lens quality. The only federal regulation concerns lens impact resistance. Voluntary industry standards are not very strict. TheAmerican Optometric Association, the American Academy of Ophthalmology and Prevent Blindness America recommend that sunglasses block 99% to 100% of UV radiation. The label should read either UV 400 or 100% UV protection.

With careful shopping you can find sunglasses that you can afford and that will fit you. Consider these useful tips when choosing sunglasses.

The glasses should be comfortable to wear. Design, color and type should be based on your activities while considering complete protection from UV rays.

Lenses should be free of distortion and imperfections. Both lenses in a pair of sunglasses should have the same coloring. FDA and the American Optometric Association suggest a simple test to check for the refraction quality.

• Hold the glasses at arm’s length and so that you can see through them clearly. Look at a straight line such as the edge of door or its frame, while slowly moving the glasses across the line. If the straight edge appears distorted, or sways, curves or moves, the lens is not optically perfect. Check to see if the coloring is even, and neither lens is darker than the other. For gradient lens, makes sure the coloring lightens gradually in the same areas of both lens.

Consider the lens’s resistance to scratching. A thin coating can be applied to lenses to make them more resistant to scratches. Plastic lenses scratch more easily than glass lenses.

Test the lens reflection to light. Anti-reflective coatings reduce the reflection caused by light that hits the back side of lenses, keeping it from bouncing into your eyes.

Sunglass frames are made from plastic, base metals, titanium, aluminum and many other materials. The frames of sunglasses should be large, sturdy, and free of rough spots. Try on lots of frame types to compare their weight and to find out which ones feel the best. Frames should be comfortable, yet fit close enough to stay in place. Test the glasses by putting them on and lowering your head. The glasses should remain in place.

The lens should be large enough to cover the eye area. Look for sunglass lenses that wrap around to your temples to keep out more light and UV radiation out. However, keep in mind that the lens or frame should not block side vision. Sometimes temples can be adjusted for better fit.

Comparison shop for sunglasses. Inspect different brands and visit more than one store. If sunglasses are inexpensive you should inspect two or three of the same brand. Some glasses on the shelf may be bent out of shape, scratched, or have other damage.

Care

To keep sunglasses in good shape, don’t clean them when they are dry. You will

drag grit across the lenses and scratch them. Use liquid soap and water. Then dry

them with a soft tissue or soft lint-free fabric. Always store your sunglasses and

eyeglasses in a case.Remember smart consumers make wise buys. Choosing sunglasses

carefully will protect your eyes and save you money.

Suggested Activities

• Ask participants to bring their sunglasses to club meeting with them. Have them tell how and why they chose their sunglasses. Discuss how effective their methods of selection were.
• Conduct a poll among friends about their sunglasses and keep a record of their answers.
• Visit a drugstore, department store and discount store. Look at the types of sunglasses available. Look for labeling information. Compare the amount of information, the cost, and brand names. Compare costs of different brands within one store. Compare the same brand at 2 or more locations. Are there differences in the prices of the same quality and brands? How do designer glasses compare in quality and cost with unbranded and non-designer brands?
• Borrow sunglasses of various types, (plain lenses, polarized, photo chromatic, mirrored and graduated). Discuss preferences and have participants compare them.
• Present a demonstration on “choosing sunglasses” for your club or county event.
• Develop judging situations and have participants compare sunglasses; quality, type and price. Have them give reasons for their selections.

Sample Judging Situation