(Photo by Tim Jaynes, Staff)
Wearing sunglasses is not only a source of comfort and fashion, but it protects the eyes from harmful Ultraviolet A and Ultraviolet B rays.
The sun, strongest between 10 a.m. and 2 p.m., is more dangerous to the eyes than what many realize. Some scientists believe long-term exposure to UVA and UVB rays can increase the chances of developing certain eye diseases such as benign growths on the eye's surface, cancer of the eyelids and skin around the eyes and photokeratitis, a temporary but painful sunburn of the cornea.
"The ozone thinning in the atmosphere has caused increased exposure to ultraviolet (UV) rays from the sun," cautioned Dr. Dan Obermark, O.D. "UV exposure can cause cataracts and retinal degeneration so protection with sunglasses is very important."
With the countless choices of sunglasses on the market today, personal preference reigns. However, it is recommended to purchase sunglasses that provide at least 98 percent protection from both UVA and UVB rays.
"A UV meter is used to measure the transmittance or absorption of ultraviolet rays and can usually be found at most offices which have large optical labs," noted Dr. Steven Barnett, O.D.
There are various colors to choose from including gray and brown which many people prefer because they distort colors the least.
"The number one selling tint is gray," said Barnett. "Gray lenses filter light equally across the color spectrum therefore they do not affect color vision. Most people desire seeing natural colors, but some prefer brown tints which enhance the reds and greens and diminish blues. I recommend brown or copper tints when patients have cataracts because blue light causes more glare problems in these patients and the brown tint filters more blue light."
Copper or brown tints are also believed to be good at blocking the blue light commonly found in diffused light such as from a cloudy day. Amber can improve both contrast and depth perception.
Yellow or amber tints are described as high intensity for maximum sight performance during low light driving such as night riding, overcast, hazy or fog conditions.
"Shooters like the yellow tint because it enhances contrast sensitivity and enables them to see their target better," added Barnett.
Rose tints help block blue which improves contrast, offering maximum light and glare protection. This tint also improves road visibility and is soothing to the eyes.
However, Obermark pointed out that many people don't understand the UV protection is not the tint. "When we apply sunscreen to our skin we cannot see it," he gave as an example. "The same is true for UV filters in sun lenses. When considering buying sunglasses, 100 percent UV protection is a must."
There are also different kinds of lenses to consider.
"Polarized lenses block reflections off of horizontal surfaces therefore allowing the surface to be seen clearer," said Obermark. "Anyone who uses their sunglasses for driving, boating, farming or skiing ought to consider polarized lenses. Another relatively new feature to sunglasses is Backside Anti-reflective treatment or AR for short. This keeps annoying reflections from interfering with your vision and allows you to see better."
Blue-blockers block blue light and usually have amber or yellow lenses. Researchers are unsure whether or not blue light is harmful but these are the most popular among skiers, hunters, boaters and pilots.
Photochromic lenses adjust to their level of darkness based on the amount of UV light they're exposed to.
When it comes to durability the Food and Drug Administration requires all sunglasses to be impact-resistant. However, not all of them are made of polycarbonate which is reportedly the most impact-resistant sunglasses material, making it ideal for people who play sports or wear sunglasses on the job.
"You absolutely get what you pay for," said Obermark. "We recently were able to acquire some Nautica brand sun wear with polarized, backside AR, 100 percent UV filter lenses and provide them for under $50. This is an excellent opportunity for patients to see how a quality lens works for about the same cost of a budget pair of sun wear."
"In most cases you do get what you pay for in sunglasses," agreed Barnett. "Many of the economy discount sunglass lenses are either warped or show refractive power which reduces visual acuity as well contrast."
Children and teens especially need protection as they typically spend more time outside and the lenses of their eyes are more transparent than those of adults, allowing more UV radiation to reach the retina, the light-sensitive layer at the back of the eyes.
Also, the effects of UV radiation on the eyes are cumulative so it's important to develop good protection habits early in life.