Sunglasses can protect your eyes from damage caused by UV radiation. The best eyewear brands produce a wide variety of photoprotective lenses. When choosing glasses, it is important to know the shape of your face:
oval face: square or “cat” glasses
round face: square glasses
square face: round glasses
Triangular face: “aviator” glasses
The bigger the glasses, the more protected the eye area is. The lenses can be polarized (great for driving or water sports) or tinted (dark lenses for mountain biking, yellow lenses for cyclists and golfers, and gray lenses offer the best vision). Good glasses can protect the eye from 99 to 100% of solar radiation. If unprotected the eyes may be susceptible to developing cataracts or macular degeneration
However, it must also be noted that a 2009 study published in the Journal of Investigative Dermatology by Sharon Moalen states that wearing sunglasses would somehow favor the development of melanomas; wearing glasses, in fact, the brain registers a lower amount of sunlight, and the body is induced to produce less melanin therefore the result is that the skin is less protected and the risk of developing skin cancer increases. This problem could be solved with the use of pinhole glasses that naturally reduce sunlight. These devices have a pyramidal distribution of small cylindrical holes (one millimeter deep) capable of blocking a large part of the oblique light rays that reach the retina out of focus. Such glasses protect the eyes from excessive exposure to light and in some cases can replace sunglasses, but they do not have UV screens. They should not be used for driving, for fast movements, in dangerous situations or when there is not enough light. Instead, they are recommended for reading, watching television or a computer screen and to get your eyes used to light again.
For information on these glasses, you can download an online user manual by Loredana De Michelis: Il vizio di rifrazione, il metodo Baters e gli occhiali stenopeici