Apabila cermin mata hitam itu digunakan untuk jangka masa yang lama, adakah kesan penapis UV beliau masih elok seperti dahulu?

If you have a favorite pair of sunglasses, you've probably used them for years. Do old sunglasses still protect the eyes from ultraviolet (UV) damage?

Kajian itu tidak secara langsung menjawab persoalan sama ada perlindungan UV semakin teruk. Satu-satunya cara untuk memastikan adalah dengan menguji cermin mata hitam anda.

Cermin mata hitam dengan perlindungan yang disyorkan akan menapis semua sinaran UV. Sinaran UV boleh merosakkan tisu permukaan mata, kornea dan kanta. Lama kelamaan, kerosakan UV boleh meningkatkan risiko katarak, degenerasi makula, dan penyakit mata yang lain. Keadaan ini boleh mengurangkan penglihatan anda.

A 2016 study from the University of São Paulo in Brazil looked at the tests to see if the UV protection of sunglasses is adequate. "This is not the same as testing whether the UV protection in sunglasses is going away," said Jeff Pettey, MD, assistant professor of ophthalmology at Moran Center University in Utah and a spokesman for the American Academy of Ophthalmology.

The researchers found that the Brazilian manufacturer's tests may underestimate the amount of UV exposure that can be caused to glasses over time. It's unclear if the findings mean anything for U.S. sunglasses testing. Brazil has a higher rate of UV radiation exposure than the United States.

While the study raises more questions than answers, Dr Petty says consumers shouldn't panic or rush to switch to their beloved shade. No one currently recommends using sunglasses in retirement.

In recent years, UV blocking technology has improved. Most sunglasses today have UV protection built into the lenses, not coated on them. If you're concerned about the age and safety of your sunglasses, you can test them at an optical store with a UV meter.

If you're ready to buy a new pair of sunglasses, Dr. Pettey offers these tips for choosing the most protective sunglasses: Look for a label that says "100 percent UVA and UVB protection" or "100 percent UV 400 protection." Choose a larger frame that covers the eyes and surrounding skin. Frames that wrap around the sides of the face provide maximum protection.