Sunglasses 101

"There are many situations here in the Okanagan where the use of sunglasses will enhance comfort and provide eye health benefits as well."

- Dr. Joel Casey

One of the many great things our patients tell us after laser vision correction is how nice it is to be able to wear non-prescription sunglasses. Some people even have multiple pairs so they can choose which ones match certain fashions or sports. A greatly expanded array of choices are offered in non-prescription sunglasses. Some of the key considerations are:

UV protection – Sunglasses should block 99 to100 percent of both UVA and UVB light. A “UV 400” label indicates that 100 percent of UVA and UVB light are blocked. The price of the sunglasses does not necessarily indicate how much UV light is blocked. Even inexpensive sunglasses can provide good UV protection.

Lens color – Lens color is a personal preference. Color does not affect ability to block UV light. “My personal favorite sunglass lens is brown polarized,” says Dr. Joel Casey. “The brown color seems to enhance contrast and make green colors more vibrant. Polarized lenses decrease reflections from horizontal surfaces such as water, roads, and snow.”

Lens transmission - This refers to how much visible light passes through a lens. A dark lens has lower transmission. Like lens color, this also does not correlate with the amount of UV light blocked. Degree of lens transmission is a personal choice based upon comfort and the type of conditions in which the sunglasses will be used. Sunglasses used when walking on a glacier should be darker than those worn for fashion.

Specialty lenses - Polarized lenses decrease transmission of light reflected from flat surfaces and are a favorite for fishing to make it easier to see into water. They are also great for driving to cut glare from roads and dashboards. Photochromic lenses are triggered by UV light to turn lighter or darker depending on the level of UV light conditions. Gradient tints are darker at the top of the lens and lighter at the bottom. Mirrored lenses decrease transmission by reflecting light from the surface of the lens.

Lens materials - Sunglasses lenses can be made from either glass, or CR-39 or polycarbonate plastic. Traditionally, glass lenses have the best optics and are the most scratch resistant but suffer from being heavy and may shatter upon impact. They are most often found in fashion styles. Polycarbonate lenses are a better choice for sports sunglasses as they are the lightest, most impact resistant and can be manufactured with a greater curvature or wrap but they are more prone to distortion and scratching. CR-39 plastic lenses are the most commonly used lenses as they are the most economical.

Frame Styles – There is a huge array of frame styles to match every fashion taste and sports specific function. Non-prescription sunglass lenses can be made with greater curvature allowing frame styles to also have more curvature or “wrap”. This gives greater protection from UV light coming in from around the sunglasses.

Cost - The price of sunglasses does not relate to how well they block UV light. Even an inexpensive pair of sunglasses can protect eyes from UV light as well as a high priced brand name style. Price influences the optical quality of the lens with higher priced lenses usually having less distortions, hard coats to prevent scratching, and anti-reflective coatings to decrease glare from light reflected off lens surfaces. In addition, price is usually evident in the quality of the frame.

Overexposure to UV light from the sun can create problems for your eyes. Sun damage can cause conditions such as photokeratitis (sunburn to the cornea), cataracts (clouding of the inner lens of the eye), pterygium or pinguecula (yellowish tissue deposits on the white of the eye next to the cornea), macular degeneration (deterioration of the central vision area of the retina), and even skin cancer on the eyelids.

"There are many situations here in the Okanagan where the use of sunglasses will enhance comfort and provide eye health benefits as well," said Dr. Joel Casey. "Information suggests that protecting the eye and surrounding tissue from UV light exposure is extremely important. The choices for non-prescription sunglasses make using them convenient, economical and most important . . . fun!”