August 1, 2006 > Don’t Let the Sun Threaten Your Precious Vision

They are invisible, yet they are everywhere in the sunlight. We know they are harmful to our skin, but did you know they can also damage your eyes and hurt your vision? They are ultraviolet (UV) rays.

UV light is a form of radiation that comes from the sun. In the earth’s atmosphere, there are two types of UV radiation. UV-A rays are absorbed by the back part of our eye. They can harm our central vision by damaging the part of the eye called the macula. Even more dangerous are UV-B rays, which are mostly absorbed by the front part of our eye - the cornea and lens.

"UV rays can cause skin cancer of the face and eyelids. They are also a known cause of cataracts and damage to the cornea and are probably a contributing factor to the development of macular degeneration," says James Cohn, M.D., a Fremont ophthalmologist who is on the medical staff at Washington Hospital. "All of these are critical reasons why you should shield yourself from UV-A and B rays."

According to the American Academy of Ophthalmology, macular degeneration is the leading cause of vision loss among older Americans. Cataracts are a major cause of visual impairment and blindness around the world. Other eye conditions that may be caused by UV rays are pterygium (a growth on the white of the eye that can eventually block vision) and photokeratosis, or sunburn of the cornea.

Whether you are young or old, everyone is at risk of damaging their eyes when they spend time in the sunlight unprotected. Those who spend long periods of time working or playing in the sun are of greatest concern.

To protect your skin when you are outside, you should always wear a good sunscreen. The best way to defend your eyes from the damaging rays of the sun is to wear a wide-brimmed hat and UV-absorbing glasses. Always aim for 100 percent UV blockage of both types of rays by your eyewear. Besides prescription and non-prescription glasses and sunglasses, this includes contact lenses and lens implants. The product you purchase should state explicitly on the label how much UV blockage it offers.

Interestingly, the tint of your sunglasses has nothing to do with the amount of UV blockage they provide.

"Tint is more for comfort and style," explains Dr. Cohn. "Tint blocks out brightness, not UV rays."   

If you’d like to know how well your sunglasses are blocking out UV rays, most doctor’s offices - like Dr. Cohn’s - have a device that can measure this. Call your ophthalmologist to ask if they provide this service.

The fit of your glasses is also an important gauge of how well they protect your eyes from UV rays. The goal is to block out any UV rays that may leak in from around the sides of your glasses. So, wraparound glasses are best.

"If your sunglasses slip down your nose just half an inch, the amount of UV rays you are exposed to increases tenfold," Dr. Cohn warns.

Most people love to spend time in the sun. When you do, be sure to you give your eyes the best protection possible.