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| Inspired by the book What's New, Cupcake? |
The majority of the sun's energy can be classified as either visible light (that we see), infared radiation (that we feel as heat), and ultraviolet radiation. Ultraviolet radiation has a shorter wavelength and more energy than visible light. There are 3 categories of UV rays: UV A, UV B, and UV C.
- UV C rays have the shortest wavelength (100-279 nanometers) and the most energy of the three. We don't hear much about UV C rays because they are, for the most part, blocked by the ozone layer.
- UV B rays have a slightly longer wavelength (280-314 nm) and are partially filtered by the ozone layer. This is the category of UV radiation that is linked to sun burns and skin cancer. In terms of the eye, most UV B rays are absorbed by the cornea (the clear part of the front of the eye).
- UV A rays have the longest wavelength (315-380 nm) of the three. Though they are lower in energy, UV A rays penetrate the skin more deeply than UV B rays and are thought to contribute to premature skin aging and wrinkling, as well as skin cancer. Most of the UV radiation that we are exposed to is UV A. Unlike UV B, UV A rays can pass through the cornea of the eye, potentially causing damage to the lens and retina.
- Beyond UV, research is being done on the effects of the sun's high energy visible (HEV) radiation, or blue light. Some studies suggest there is a possible association between exposure to large amounts of blue light and the development of macular degeneration, a disease in which the tissue of the back of the eye that is responsible for your central vision (the macula) is damaged, thus leading to vision loss.
- In the short term, intense exposure to UV radiation while unprotected can cause a condition called photokeratitis. Also known as snow blindness or UV keratitis, photokeratitis is essentially a sunburn of the eye. The symptoms usually begin a few hours after exposure, and they include pain, redness, tearing, and light sensitivity. It is a temporary, but very unpleasant, condition.
- The most dangerous effects of UV radiation occur over time. Because damage from UV radiation is cumulative, it is important to develop good sun safety habits early on in life. Here are some examples of conditions that are thought to be linked to long-term UV exposure:
- A pterygium is a benign growth of the conjunctiva (the tissue covering the white part of the eye) that extends onto the cornea (the clear part). Surgical removal may be advised if the pterygium interferes with vision. A pinguecula is a similar finding, but it is confined to the conjunctiva and does not extend onto the cornea. It appears as a yellow-ish raised nodule on the white of the eye.
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| Pterygium |
- Exposure to UV radiation is thought to play a role in accelerated cataract formation (clouding of the lens) and retinal damage.
- Beyond that, skin cancer can also develop on the eyelids or on the skin around the eyes. The Skin Cancer Foundation reports that eyelid skin cancer accounts for 5-10% of all cases of skin cancer, with basal cell carcinoma being by far the most common.
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| Basal cell carcinoma |
- Protect the little ones! Kids spend a lot of time outdoors, and the lenses of their eyes allow more UV radiation through to the back of the eye when compared to adults. As mentioned before, UV damage is cumulative, so be sure to start protecting the eyes early! The Vision Council reports that 25% or more of an individual’s lifetime exposure to UV radiation occurs before age 18.
- Check the labels. Whether you are looking for sunglasses for yourself or your kids, be sure to purchase sunglasses that block 99-100% of UV A and UV B rays. The darkness of the lens is not an indication of how much UV-blocking action you have, so be sure to check the labels. The label may read 100% UV protection or UV 400 (meaning it blocks rays shorter than 400nm).
- Talk to your optometrist and optician about your outdoor activities. There are several options available in terms of prescription sunglasses, so your best bet is to speak with your eye care professional and determine which is best for your lifestyle. Polarized lenses are designed to reduce glare and reflections off of surfaces like water, snow, or pavement, so they are an especially good choice for boaters, fishers, and skiers. If you wear prescription glasses, there are coatings that can be placed on the front and back of lenses to block UV radiation and reflections. Additionally, you can opt for photochromic lenses (Transitions is a well-known brand) that darken on exposure to UV. There are clip-on/magnetic sunglasses that can attach to your glasses as well. So many options!
- Contact lenses that block UV radiation are available. The Food and Drug Administration (FDA) puts UV blocking contact lenses into two classes: Class 1 UV blockers absorb over 90% UV A and over 99% UV B radiation, and Class 2 UV blockers absorb more than 70% of UV A and more than 95% of UV B radiation. Ask your optometrist about what options are available for you. Wearing contact lenses that help block UV radiation does not replace the need to wear sunglasses, as contact lenses do not cover the whole eye and do not protect the eyelids.
- Last but not least, wear a wide brim hat to minimize the amount of exposure your eyelids and eyes have to harmful UV radiation. Wrap-around sunglasses help in this regard too, as they are more fitted to the face and prevent peripheral rays from reaching the eye. Be sure to take precautions even if it is not particularly sunny outside. While peak sun hours are between 10am and 2pm, it is believed that the eyes receive the most UV exposure in the hours directly preceding and following this time period, due to the angle of the sun in relation to the eyes.
Enjoy the summer season safely!
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