How To Protect Your Eyes From UV Radiation

Summer is officially here and it’s that time of year again when we are spending more time outside enjoying the warm weather. We’ve all heard that we should wear sunglasses to protect our eyes when we are outside, but what exactly are we protecting our eyes from? We know that UV radiation can cause sunburn and skin cancer, but how does it affect the eyes?

As professional optometrists in Calgary SW, we want to educate the public on how UV radiation can impact our eye health and choosing the right sunglasses. Keep reading to learn more about how you can prevent serious eye health issues from UV exposure.

What is ultraviolet (UV) radiation?

First, it is important to understand what UV or ultraviolet radiation is. Both UV and visible light are components of the electromagnetic spectrum that includes radio waves, microwaves, infrared radiation, x-rays and gamma rays.

One unit of measurement used to quantify these various forms of radiation is the wavelength measured in nanometers (nm):

The visible light spectrum spans from 400 to 700 nm

  • UVA spans from 320-400 nm
  • UVB spans from 280-320 nm
  • UVC from 220-280 nm

The smaller the wavelength, the more energy the wave has. It is this increased energy that contributes to UV radiation’s ability to damage human tissue. Most of the radiation that reaches the Earth from our sun is in the form of infrared (heat), visible light, and ultraviolet light. Our atmosphere filters out all of the UVC and the UV radiation that does reach the Earth - approximately 95% is UVA and 5% is UVB.

Due to ozone-depleting substances, more UVB radiation reaches the Earth’s surface now than prior to the use of these substances. However, these substances have now been banned and the Earth’s ozone layer is recovering, which is good for our eye and skin health.

Protecting your eyes from UV radiation

When considering how to protect our eyes from ultraviolet radiation, understanding how and where we get our exposure to UV radiation is important. You may have heard that the peak exposure time of our skin to UV radiation is between 10:00 AM and 4:00 PM. However, research has shown that for our eyes, the peak exposure times are different.

Typically, the eyes’ peak exposure times are between 8:00 - 10:00 AM and 2:00 - 4:00 PM when the sun is not directly overhead. Also, because we typically avoid looking directly at the sun, our eyes receive more scattered or reflected UV radiation than direct UV radiation. The amount of scattered or reflected UV light in our environment is high because the shorter the wavelength of the radiation, the more it is reflected or scattered by the atmosphere and various surfaces.

In fact, the sky appears blue not white because the blue light, which is the shortest wavelength of visible light, is scattered more than the other colours of light. UV radiation is reflected or scattered from particles and molecules in the air, off the edge of clouds, and by surfaces such as snow, water, concrete and wood.

UV radiation can even reflect toward our eyes from the back of our eyeglass or sunglass lenses. Some antireflection coatings put on eyeglass lenses to reduce glare and increase the transmission of visible light through the lens actually increase the amount of UV radiation reflected from the back surface of the lens toward the eye by up to 50%. Therefore, even when we are facing away from the sun or when we are in the shade, our eyes’ exposure to UV can be high.

The risk of UV radiation exposure to our eye health

UV radiation exposure can cause or contribute to a variety of health issues for the human eye, including:

  • Sunburn of the eyelids
  • Skin cancer of the eyelids - Three common forms of skin cancer of the eyelids are basal cell carcinoma, squamous cell carcinoma, and melanoma. Skin cancer is the most common cancer in Canada. 5-10% of total skin cancers occur on the eyelids.
  • Photokeratitis - Damage to the corneal and conjunctival epithelial cells that causes the death of these cells. Photokeratitis causes symptoms of eye pain, redness, eyelid swelling, light sensitivity, tearing, and blurry vision. These symptoms usually begin 1-12 hours after excessive UV exposure.
  • Pinguecula - A degeneration of conjunctival tissue due to exposure to sun, wind, or noxious chemicals. The conjunctiva is the thin, transparent tissue covering the sclera or white part of the eye. When this tissue starts to degenerate, it becomes raised and opaque. It can also become inflamed, which is a condition called pingueculitis.
  • Pterygium - A degeneration of the conjunctiva that has progressed to the point where the thickened tissue has grown over the cornea. The cornea is the clear dome on the front of the eye that we see through. If the pterygium grows so far over the cornea that it starts to block light going through the pupil, then vision loss and glare issues can result.
  • Cataract - A clouding of the lens inside the eye.
  • Age-related macular degeneration - A degeneration of the part of the retina called the macula. This is the part of the retina we use when we are looking directly at something and that allows us to see the most detail. Macular degeneration causes damage and death to a layer of retinal cells called the retinal pigment epithelium (RPE.) These cells are critical to keeping our photoreceptor cells healthy, and without healthy photoreceptors, we lose the ability to see.
  • Choroidal melanoma - A tumour of a layer of the eye called the choroid. There is no conclusive evidence that UV light contributes to choroidal melanoma, but we do know that UV exposure does cause skin melanomas. Both of these tumours are cancer cells called melanocytes.

With this long list of negative effects of UV radiation on the eyes, it makes sense to do what we can to protect our eyes from exposure to this radiation.

Optometrist-recommended eye protection

Wearing UV 400 or 100% UV blocking sunglasses is important all year round, - even on cloudy days or when in the shade. These sunglasses should be as large as possible to cover as much of the skin around the eyes as possible. They should also fit as close to the eyes as possible to limit the amount of UV radiation that gets to the eyes around the frame. Sunglasses that wrap around the face prevent more UV radiation from reaching the eyes than flat sunglasses.

Also, the antireflection coating being used on your lenses can impact the amount of UV radiation reaching your eyes as discussed above. The good news is that some of the newer AR coatings that come with UV protection are designed to reflect the UV radiation that reaches the front of the lens and absorb most of the UV radiation that reaches the back of the lens.

Recently, a helpful system for describing UV protection in eyeglass lenses has been developed. This is called the Eye Sun Protection Factor (E-SPF.) E-SPF is similar to the SPF factor we are all familiar with. This number indicates the amount of UV protection that the lenses provide compared to not wearing any lenses. Just like the SPF factor, the higher the number, the better the protection.

Be sure to ask your eye care provider if the sunglass lenses you are buying have an E-SPF number. If you have questions or concerns about protecting your eyes from ultraviolet radiation, feel free to call our clinic to book an appointment with Dr. Doig or Dr. Chorel for an assessment and recommendations.

Thank you to the Canadian Journal of Optometry, Volume 79, no. 2, article Sun Safety and the Eyes for providing much of the information in this blog.

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