Eye Effects in Calgary & Didsbury
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What Does Your Sunglasses UV Rating Really Mean?

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When choosing sunglasses, most people choose based on style and how they look. Don’t get us wrong – fashion is important. But what’s even more important is the protection of your eyes from harmful UV rays. Luckily, there is a way to accomplish both – if you know what to look for.

What Are UV Rays? A Science Lesson

Simply put, electromagnetic radiation is solar energy that is emitted by the sun. There are seven types of energy in the electromagnetic spectrum:

  • Gamma Rays
  • X-rays 
  • Ultraviolet light (UV rays)
  • Visible light 
  • Infrared light 
  • Microwaves 
  • Radiowaves 

Each type of energy is measured by differing wavelengths and energy levels and do very different things. For example, visible light allows us to see the world, while infrared radiation enables us to feel the warmth of the sun. 
And while there are some slight positive benefits to UV rays – it provides us with Vitamin D and has been shown to improve mood – its harmful effects are hard to ignore. In fact, it has been proven that 65% of melanomas are caused by UV radiation exposure

Types of UV Rays

  • UVA rays make up about 95% of the sun’s UV rays. These rays penetrate and affect cells deep in our skin layer, causing premature wrinkles and cancer
  • UVB rays make up less than 5% of the sun’s UV rays. They are stronger but affect cells in the top layer of the skin. They are the main cause of sunburn 
  • UVC rays have the shortest wavelength range and are blocked by the earth’s atmosphere

Often times we talk about how harmful UVA and UVB rays are to our skin but gloss over what it is doing to our eyes. 

UV Rays & Our Eyes

Similar to how UV rays penetrate our skin in different ways and at different depths, the same is true of our eyes. According to The Government of Canada, our eye absorbs light in three different ways. 

Harmful Effects

Our eyes are an extremely sensitive organ and any overexposure to UV radiation can be extremely dangerous. Although resilient, if our eye cannot repair itself after exposure, the following can occur:


Overexposure to UV rays has been linked to cataracts, a condition where the normally clear lens of the eye becomes cloudy and opaque.

Eye or Eyelid Cancer

UV rays have been linked to certain types of eye melanomas, such as intraocular melanoma and squamous cell carcinoma of the conjunctiva.

Keratitis (Corneal Sunburn)

Overexposure to UVB rays can quickly cause the cornea to burn. Also known as snowblindness, this condition is very painful and occurs often in our Alberta climate because of the sun’s intensity and reflective nature off of snow and ice.
If eyes are overexposed to UV radiation, the front portion of the eyes can be damaged. If visible light is too bright or intense, or if you stare directly at the sun, even briefly, the retina can be damaged, causing permanent loss of vision. UV radiation, along with wind and drying of the eye, may cause snow blindness, an uncomfortable but temporary condition.

Sunglasses: Screen Your Eyes

As optometrists, we can’t overstate the importance of protecting your eyes from harmful UV rays. And the best way to do this is to wear sunglasses as often as possible, even in cloudy weather.
When choosing sunglasses, they should have a rating of at least UV 400. This will block up to  99-100% of UVA and UVB rays, as ultraviolet radiation has a wavelength range from 100 to 400 nanometers. 
Any rating less than this will put your eyes at risk. Luckily, every pair of sunglasses we offer has complete UV protection. This includes our huge range of brands, including designer sunglasses and photochromic (transitional) contact lenses and eyeglasses. 
Come see us today at our Calgary or Didsbury locations. Our expert staff will find you a pair of sunglasses that look great and protect your vision. 

Written by Dr. Rod Adams

Dr. Rod Adams is a graduate of the University of Alberta and the University of California at Berkeley School of Optometry. Dr. Adams has been in private family practice since 1997. During this time, he has developed a strong interest in pediatric optometry and laser corrective surgery options.
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