January 17, 2007
Over the last few decades, Federal regulations have set up safety requirements for eyeglasses in order to protect the consumer. All lenses must have a certain degree of impact resistance; the thicker the lens, the safer it will be. Different lens materials require different thickness in order to meet these standards. Glass lenses are the most breakable and therefore must be thicker than plastic. This is why we rarely utilize glass lenses; the weight is usually uncomfortable to wear all day.
In addition, even with the thicker lens, glass can shatter, possibly causing serious eye injury. Even plastic, although much safer, can crack into sharp edges. A plastic material called polycarbonate is recognized to be the safest lens material available. Where a projectile can crack plastic and shatter even safety glass, polycarbonate will simply deform at the point of impact. This is why we recommend polycarbonate, especially for children who wear their glasses all or most of the time. The additional advantage of polycarbonate is that they are lighter and thinner, and block nearly 100% of harmful UV rays. UV rays have been associated with cataracts changes to the surface tissues of the eye. With changes in the ozone layer, the long-term effect of ultraviolet exposure is almost certainly going to become more of a factor in eye care.
Regardless of how sturdy you believe your glasses are, there are certain occupations and activities for which normal dress frames are simply inadequate. Most sports, and any contact sport, demand the use of prescription goggles. They are designed to fit close to the face to insure protection from the sides. An elastic band secures the goggle, rather than metal or plastic temples that can bend or crack when hit. In addition, a rubber nose guard helps reduce the risk of injury. Some sport goggles are specially to fit under a helmet, making them especially useful for football players, motorcyclists, etc. Of course, polycarbonate lenses are required as well.
Goggles are of special importance in racquet sports. A racquetball is just the right size to fit into the eye socket, just small enough to get past the orbital bones around the eye socket that normally protect the eye from injury. Even if you do not require prescription eyeglasses, racquetball and squash players should always wear protective eyewear.
Industrially approved safety glasses are more like regular eyeglasses. They will tend to be larger to afford better eye protection. The frames are thicker and often will come with side shields. Welders, especially arc welders, require specially coated or tinted lenses to block infrared light (the opposite end of the spectrum from ultraviolet), which will penetrate deep into the tissues of the eye. Never weld without eye protection!
Sports goggles and safety glasses are not designed to be pretty. They're safe and practical, and have an important niche in an active life.