Just as there are different styles and shapes of sunglasses, there’s a wide variety of lenses to choose from. Each of these differ in the way they protect your eyes from the damaging effects of the sun. To get the right pair of sunglasses with the right lenses for your specific lifestyle, here is a brief description of what’s available:
Blue-blockers block blue light or high energy visible light. This type of light has been liked to age-related macular degeneration – a disease that gradually destroys sharp, central vision and is the leading cause of blindness in Americans 60 years and above. These lenses are recommended for skiers, boaters, pilots and hunters.
Polarized lenses and anti-reflective coatings cut reflected glare – a blinding light that reflects off snow, water, concrete or glass. This type of light is annoying and forces your eyes to work harder. Polarized lenses block glare and are good for driving and outdoor activities in the snow or water. However, these sunglasses can make reading liquid crystal displays difficult.
Polycarbonate lenses are normally found in sports goggles. This type of lens is impact and scratch-resistant but not necessarily scratch-proof. It provides adequate protection from ultraviolet (UV) light and will protect your eyes from injury since this is the same material used in aircraft windshields Polycarbonate lenses are lighter than glass lenses but 50 times stronger.
Photochromic or photochromatic lenses change from dark to light depending on the surrounding light. They adapt to changing lighting conditions and may react to temperature as well. They become darker outdoors and lighter indoors. Early models were made of glass but you can now get polycarbonate and plastic photochromatic lenses.
“The active ingredient that causes the lenses to transform is called silver halide and is mixed evenly throughout the lens. This means the whole lens will change when exposed to light. It also means that if a particularly strong prescription is made, the strongest, thickest part of the lens will be darker than the thinner parts. Also, if there is a large difference in prescription between the two eyes, the lens with the stronger prescription will be darker than the weaker one,” explained Liz Martinez DeFranco, an instructor in the opticianry program at Interboro Institute in New York City.