Expiration dates are very important. They tell us when to throw away foods that are no longer safe to eat, when to replace medications and vitamins, when to buy new cosmetics, and even when to change the oil in your car. But what about sunglasses? Do they have an expiration date, or can they be worn indefinitely?
“The answer is not so simple. To protect your eyes effectively, sunglasses must be coated with special filters that absorb ultraviolet (UV) radiation. However, over time and with prolonged exposure to UV radiation, these filters show a gradual decrease in their protective effect,” says Dr. Anastasios-I. Kanellopoulos, MD, is an ophthalmic surgeon, founder and scientific director of the LaserVision Institute of Ophthalmology, and professor of ophthalmology at New York University.
Exactly when this reduction in protection will occur is not known exactly, because it depends on the frequency and duration of sunglasses use, as well as the intensity of UV radiation during use. A few years ago, scientists from Brazil published a study that showed that in a country as sunny as theirs, sunglasses lose their protective effect within two years of daily use for several hours (approximately 2 per day). news4health.gr.
“Think of sunglasses like sunscreen,” says Kanellopoulos. “They are as important to eye health as the sunscreen we put on our skin. But just as putting on sunscreen isn’t enough if one is going to be out in the sun all day, a pair of sunglasses for daily use over many months and years isn’t enough.”
What does this mean in practice? “The general rule is that the older the sunglasses, the more likely they are no longer adequately protecting the eyes,” the professor replies. – For this reason, a preventive check of their protective ability in the optics salon is recommended. Many of them have special devices that measure the degree of protection (what it is at the moment). If your sunglasses are absorbent, they will filter the entire UV spectrum, providing 99-100% UVA and UVB protection.”
An alternative solution for those who do not want to measure the UV filter of their glasses is to replace their sunglasses approximately every 2 years if you wear them every day, winter and summer, for a few hours outdoors.
However, you must be very careful when choosing a new pair of sunglasses. The price, design, and color of their lenses may be the main criteria by which we usually choose glasses, but none of them are the most important for protecting our eyes from UV damage.
“For sunglasses to be reliable, they must first and foremost claim to offer 100% UVA and UVB protection, or UV absorption down to 400nm,” says Kanellopoulos. – They should also be large and fit well on the face to protect the eyes and from UV reflections that enter the eyes from different angles. Therefore, the most suitable glasses are those that cover most of the face and also protect the eyes from the sides.
The color of the sunglasses lenses is essentially irrelevant. Darker glasses do not mean that they protect your eyes better than lighter ones. And vice versa, sunglasses without a good UV filter can be more damaging to the eyes because the dark environment they create causes the pupil to dilate, allowing more harmful UV radiation to enter.
Lens color only matters if you play outdoor sportssuch as golf. In such cases, you may need sunglasses with green, grey, brown, pink, or amber lenses as they increase contrast and make exercise easier.
Another factor that is not a measure of the quality of protection is the price of glasses. Expensive glasses don’t necessarily mean they protect, and cheap glasses don’t necessarily mean they don’t fit.
The fact, where do you buy sunglasses, not how much they cost. Therefore, be very careful when buying optics from street vendors, online, flea markets, etc. The best option is to buy sunglasses from specialized stores so that you know all their quality characteristics.
If you prefer sunglasses with polarized lenses, be aware that they reduce glare from smooth surfaces (e.g. asphalt, water, sand). But that doesn’t mean they provide UV protection. Therefore, even sunglasses with polarized lenses should have a special filter to maximize UV absorption.
In addition, sunglasses, no matter how reliable they are, cannot protect your eyes if you look directly at the sun, so never, ever do this,” concludes Mr. Kanellopoulos.