Military Ballistic Performance
The various branches of the U.S. military have recognized for many years that eye injuries are an inevitable by-product of their many activities. This is true not just in combat situations, but in a variety of support activities on flight lines, in maintenance settings and in special operations. Protection is required for ballistic impact protection, chemical protection and for radiation protection from sunlight and high energy lasers. Over the past 5 to 6 years, the U. S. Army particularly has championed the use of high performance spectacles as general issue gear for all deployed personnel. There is an increasing selection of military ballistic rated safety glasses and goggles that have been approved and have seen extensive use in Afghanistan and Iraq where improvised explosive devices (IEDs) are a constant threat.
The Army specifies that protective eyewear comply with Military Standard 662 which outlines a number of ballistic fragmentation tests for different classes of products. The test consists of firing a special shrapnel simulating projectile at a specified velocity. The fragment is cylindrical and has an angled face that will burrow into the product. For ballistic spectacles, the fragment is 0.15 caliber and the velocity of the projectile is 650 +/- 10 ft/sec (440 mph). In this case, the test protocol specified is as “V0” (V-Zero). This means that no (zero) impact failures are allowed at the velocity specified. The spectacle is impacted once, at a point coinciding with the center of either the left or right eye. The lens cannot fracture, nor can the projectile penetrate to the eye. The impact energy of this test is about 7 times that of a ¼ inch steel ball traveling at 150 ft/sec.
One may wonder if this test is too extreme for eyewear meant primarily for industrial use. The way to look at this is the added level of protection and security afforded by products offering V0 impact performance. For example, the obvious impact hazard may be particulate generated by an operation such as grinding. The less obvious threat is the explosion of the grinding wheel which can send shards of material flying at speeds considerably higher than ANSI standards test. While many spectacles can meet the minimum performance of industry standards, higher performing products offer better protection to give you a fighting chance in case of unforeseen accidents. (No product is unbreakable or impenetrable given high enough impact energy, and additional protection such as goggles or faceshields may be necessary based on the workplace hazard assessment).
Additional protection will make sense, and certainly be appreciated, in other applications including EMS, law enforcement and homeland security. The proper combination of design, materials and controlled manufacturing processes will yield superior impact protection in products that are at the same time stylish, comfortable and a great value given the level of protection delivered.