Sun exposure can damage eyes as well as skin. Ultraviolet radiation (UVR) can cause cataracts, degeneration of the retina, melanoma of the eye, and blindness. Sun protective eyewear can significantly reduce UVR exposure to the eyes. Sunglasses, eyeglasses and contact lenses that block 99-100% of UVA and UVB are types of recommended protective eyewear.
Sunglasses, no matter how little they cost, can provide excellent protection from UV rays. The percentage of the UVR filtered out by sunglasses is usually printed on the label. While there is no universal labeling of sunglasses in the U.S., look for those that provide 100% UVA/UVB protection. The label may also say something like "UV absorption up to 400nm" or "absorbs UV up to 400nm" which is equivalent to blocking at least 99% of UVA and UVB. Sunglasses are regulated by the FDA and must also comply with impact-resistant requirements and labeling regulations. They are tested with special transmittance equipment, not on human subjects like sunscreen.
Choose sunglasses that are close-fitting and large enough to shield your eyes from many angles to help block scattered, reflected, or refracted UV light. Darker lenses and polycarbonate, polarized, and blue-blocking lenses are not necessarily more protective. People who wear prescription glasses can have a UVR protective coating added to their lenses. Be sure to bring some sort of eye protection along with you on your vacation. If you forget to pack your sunglasses, check out the resort gift shop!