You have been researching and carefully surveying the market for sunglasses till the perfect specimen is found. Just when the compliments begin to pour in, and you’re congratulating yourself on the purchase of a lifetime, you encounter Mr and Mrs Parsimony – your average economy-driven couple bent on extolling frugal living. You are either with them, or against them. Sound familiar?
Many people view sunglasses merely as tools to block harsh light or glare from the brilliant sun; the concern of invisible ‘UV’ radiation is regarded a distant obscurity at best. The uninformed thus often fail to rationalise the expenditure of several thousands of rupees for a simple ainak and end up participating in the stout popularity of generic sunglasses being sold by local vendors.
• Ultra-violet or ‘UV’ rays are a kind of radiation from the sun, with UVA and UVB types being of concern. The former causes the most harm, as the latter is also absorbed by the ozone. With the depletion of the ozone layer, however, humans are being exposed to progressively increasing levels of UVB as well.
• UV radiation is most intense in spring and summers; less so in fall and least intense in winters. It peaks daily between 9am and 3pm. It increases significantly with altitude; is highest near the equator and is not absent in hazy or cloudy weather.
• UV rays can be absorbed from not only direct (ambient) sunlight but also reflected (incidental) sunlight, ie light, which bounces off surfaces such as water, snow and sand. Incidental sunlight is a far more significant source of UV exposure for humans than the direct sun.
According to ophthalmologists, persistent, exposure to UV rays is strongly associated with a variety of diseases of the eyes. This includes macular degeneration — the foremost cause of blindness amongst old people — skin cancer of the eyelids, and cataracts. Children, old people and those working outdoors are at most risk.
Wearing cheap generic sunglasses does not help — in fact, it can be severely counterproductive. The darker the tint on the lens, the more one’s pupils will dilate to allow in light. And with no UV blocking coating on the cheap sunglasses, one inevitably absorbs more UV radiation than if they were sunglasses-free.
What to do
• Find sunglasses that have UV blocking. According to the American Academy of Ophthalmology, you should buy sunglasses that block 95 to 100% of UVA and UVB rays.
• Don’t be fooled by colour or cost. Sunglasses that are darker don’t necessarily block more UV light — the shade of the tint doesn’t ensure protection (UV coating is an invisible layer) and neither does price. You should hunt for the label: “UV absorption up to 400nm” — which is equivalent to 100%. Be wary of sunglasses that claim to offer UV protection but do not state exactly how much.
• Explore convenient options. Transitions Optical, a US based firm specialising in high-tech eyewear, has introduced the first photochromic lenses — an adaptive type of lenses which darken upon exposure to UV radiation and reverts to clear when unneeded.
Special note: Children’s eyes are most vulnerable to UV radiation. The lens in a child’s eyes is more transparent than an adult’s and allows significantly more light in. Considerable evidence indicates that, in diseases of the eye that result from cumulative overexposure to UV radiation, upto 80% may accrue during childhood. With proper care, such diseases can both be delayed and prevented. Don’t neglect your child’s future by overlooking the use of protective sunglasses.
Lastly, for people living in low latitudes, be especially careful of this combination: overcast weather, snow-clad streets and high altitude. Case in point: Murree!
The authors are involved in a project called Scholars By Profession which intends to pioneer introducing graduate-level research to Pakistan. Please visit their Facebook page for further details.
Published in The Express Tribune, August 13th, 2012.