Sports Trader
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Know your gear


Eyewear = eye protection

By CARIN DU TOIT
August 2005

It is very important to look after one’s eyes. Everyone knows that — and therefore there is a growing demand for activity-specific eyewear amongst sport and outdoor enthusiasts. However, with so many different sunglasses on the market and each one promising to be the best of the best, the question is: which eyewear should a retailer stock to meet the needs of his customers?

Nowadays, there are lenses for every conceivable light condition and environmental factor, and a frame to go with each possible lens. It is near impossible to stock each one. Thus, focus on the eyewear that goes with the equipment or apparel you already stock — after all, the equipment already attracts a customer who participates in a certain sport.

The first step is identifying which sport and what dangers the sport presents with regards to one’s eyes.

In the active outdoor and sporting environment protection against eye injuries as well as environmental factors needs to be considered, advises Prof Jannie Ferreira of the Academy of Sports Vision, Department of Optometry, RAU in an online article Selecting Protective Eyewear for Sport.

Thus, by identifying the athlete’s exposure to the sun, wind, dust, or other environmental factors that might affect the eyes and interfere with performance, it will be easier to identify what type of lens, coating and other special frame requirements the athlete needs.

Ultra violet radiation

An absolute must for all eyewear is UV protection. UV (ultra violet) radiation is the spectrum of invisible light between 286 and 400 nanometre (nm). Its source is not only the sun, but also fluorescent light, xenon arc lamps and other sources of light.

UV is divided into three segments: UVA (320 – 400nm), UVB (286 – 320nm) and UVC (below 286nm). The cornea can filter out UV radiation below 300 nm. Constant exposure to UV radiation of 300 – 400nm could result in photochemical eye damage, which over time could result in the development of brown or sunshine cataracts (keratitis) and other eye health problems. It is estimated that 10% of all cataracts are caused by UVA and UVB exposure.

    » UVA is the least harmful and most commonly found type of UV light, because it has the least energy. UVA light is often called black light. Most phototherapy and tanning booths use UVA lamps.
    » UVB is the most destructive form of UV light, because it has enough energy to damage tissues, but not enough to be completely absorbed by the atmosphere. Most UVB light is blocked by the atmosphere, but a small change in the ozone layer could dramatically increase the danger of skin cancer, which UVB is known to cause. Combined with cold wind and snow, UVB has the potential to cause snow blindness (photokeratitis), a temporary but painful problem in the cornea of the eye, lasting 12 to 48 hours. There is some research that suggests that daily exposure to UVB in very bright sunlight over a period of many years may cause a gradual clouding of the lens of the eye, however, not everyone agrees on this.
    » UVC, the shortest wavelength of the UV rays, is almost completely absorbed in air within a few hundred meters.

Lens technology

One hears a lot about polarization and that it is good to have, but what is it and what does it do?

When you rotate a pair of polarizing sunglasses, you will find that they cut glare better in some positions than others. This is because when light reflects from water, asphalt, or other non-metallic surfaces, it becomes polarized — where the reflected light is usually vibrating more in one direction than in others. Horizontal surfaces reflect light that vibrates horizontally, and, vice versa. Polarizing lenses absorb the horizontally orientated glare, because the polarizers in the lens are vertically orientated. Polarization in a lens lets through light that is vibrating in one direction and absorbs light that is vibrating in all other directions, thus one sees a clear image.

Polycarbonate lenses are plastic lenses that are strong and impact resistant. Not only are these lenses thinner and weigh lighter than traditional plastic lenses, they have built in UV protection properties and are scratch resistant.

Less of the polycarbonate material is needed to provide the same amount of visual correction that a traditional lens offers. Thus, the polycarbonate lens is thinner and lighter in weight.

Polycarbonate lenses are impact resistant because they are flexible and gives slightly under pressure without breaking. These lenses are made out of the same material as bullet-proof glass.

When looking at the lens colour, it is useful to remember that the darker the tint, the more light it absorbs. A photochromic coating is often used for cycling or running eyewear, where one moves between shadows and the outdoor light is unpredictable.

The alternative to a photochromic coating is keeping multiple sunglasses for different light conditions, or to have interchangeable lenses that can be changed with the light.

Sports eyewear does not only protect the eyes from harmful elements, but they also enhance the sportsman’s ability to do the sport. Certain lenses can enhance certain colours, depending on the colour of the lens, for example teal lenses block out most colours and enhance yellow, which makes it perfect for a sport such as tennis, where one needs to concentrate on the yellow ball and do not need to see the other colours as clearly.

Others provide good contrast, which is good for a sport such as skiing, where one needs to see dents and rises in the surface.

Except for the lens and the coatings, there are other considerations to take into account. A pliable brow bar keeps the frame snug against the forehead. This eliminates perspiration and keeps debris from the eyes. If one needs to wear spectacles to see properly, no problem — fitovers are sunglasses that are designed to be worn over one’s spectacles.


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