To see another day.
Not only can eye injuries reduce an individual's fighting capability to nil, but in many cases can also cause irreversible damage. According to American statistics ten per cent of injured soldiers can be expected to present eye injuries, while other sources state that 90% of those could have been avoided had the victims been wearing suitable protective eyewear.
However, providing the soldiers with eye protection devices is good enough, because if they are not good-looking and trendy only few will wear them. Thus while protection, optical performances, wearability. integration with sighting equipment and durability remain decisive parameters in a choice, design now heavily cuts into the equation, especially as glasses are worn for much longer periods of time than goggles, which are mostly used during operations.
Numerous, if not too many, standards are available to establish the minimum protective levels for eyewear. Among those are Nato and American military standards, although one document that is always kept in consideration by most manufacturers is the one issued by the American National Standard Institution and Industrial Safety Equipment Association (Ansi/Isea).
While Nato Stanag 2920 defines the testing procedures for a wide range of equipment, the Stanag 4296 rule establishes eye protection criteria for the individual soldier and states, * protection must be offered against small fragments resulting from the explosion of a typical HE-shell or mortar at a distance of 30 metres with a typical weight of 325 mg and a speed of 215 m/s *. Comfort, weight, mist and field of vision considerations follow, the field of view requirement being 80[degrees] on both sides *for optimum use of peripheral vision *.
Compatibility with protection items aimed at defeating nuclear light and heat flash, NBC agents and laser radiation is also required. In addition, Stanag also requires compatibility with sighting and telecommunication systems. In the American forces, MIL-DTL-43511D is based on the 0.22 calibre T37 shaped projectile with a weight of 17 [+ or -] 0.5 grain (1102 mg [+ or -] 32 mg) at a speed between 168 and 171 metre/sec. However, this ballistic parameter is far from being sufficient for a goggle or eyewear to be accepted in the military.
A series of other optical and mechanical tests also take prismatic deviation, refractive power, luminous transmittance, optical density, optical distortion, haze, ultraviolet transmittance, chromacity, abrasion, coating adhesion, weathering and chemical resistance into consideration. Another standard, the MIL-PRF-31013 uses for ballistic tests a 0.15-calibre 5.8-grain (376 mg) projectile at 201 to 207 metre/sec.
At any rate and as mentioned above, the most widely considered reference standard for eye protection remains the Ansi/Isea document Z87. On 13 April 2010 a new version, the Z87.1-2010, was issued with the principal aim to shift from the previous categorisation that was organised by type of protector, towards a hazard categorisation, thus helping users to select the appropriate protection.
Other changes have also occurred: the new standard envisages an extended side protection - products are now either impact or non-impact protectors (the basic and high-impact categories have been abolished as well as those of primary and secondary protectors) - and additional product testing such for special environments have been added.
Impact rated protectors must withstand a series of tests including, inter alia, high mass impact, resistance to a pointed projectile weighing 500 grams dropped from a height of 1.27 metres, high velocity impact, resistance to a 6.35 mm steel ball travelling at 46 metre/sec and so forth.
Lens mountings must also pass high mass and high velocity impact tests. Following the adoption of the 2010 release, the markings have also been updated (as summarised in the table below).
Turning to the lenses themselves, the most widely used material is the bisphcnol type of polycarbonate plastic using moulding materials conforming to ASTM D 3935. With weight always a concern in the military (as well as in other fields such as sports), glass and plastic lenses have been replaced by polycarbonate types. Not only arc these thinner and lighter, but they also are ten times more impact resistant and provide 100% protection against ultraviolet light.
Developed in the 1970s for space applications, this material is now standard issue for ballistic glasses. Highly flexible, polycarbonate lenses are made by injection moulding and are scratch-resistant through a surface hardening treatment. Another material used for ballistic lenses is NXT, a materiel developed in the early 1990s in America specifically for military purposes by Simula Technologies (since then acquired by Armor Holdings, now part of BAE Systems). Used for example in Apache windshield panels, NXT lenses are obtained by casting, a process that reduces internal stresses and thereby guarantees high optical homogeneity and mechanical stability. According to Simula Technologies data, NXT impact resistance is 34.8% higher than polycarbonate and ten per cent lighter.
The main market for military protective eyewear remains North America, thus it is not a surprise that most producers are based in that region. The US Army Updated Authorized Protective Eyewear List (Apel) for Military Combat Eye Protection contains overall some 15 different models of eyewear both for users with prescription lenses and without, and goggles.
The most widely used military spectacle in service today is probably the Sawfly, manufactured by Revision in Vermont. A purpose-built military spectacle with interchangeable lenses that provides unrivaled protection against ballistic, ultraviolet and laser threats. Over 2.5 million sets of Sawtlys have been fielded in seven countries including the United States, Canada, the Netherlands, Germany, Belgium, Denmark and recently Great Britain. This number should increase, as Sawfly spectacles are being delivered to Austria, Portugal, India, Singapore. Kuwait and Korea.
Available in two sizes, the Sawfly features interchangeable lenses (clear, solar and high contrast). An Rx carrier for prescription lenses snaps into the Sawfly spectacle, this carrier is also compatible with Revision's Desert Locust goggle. Selected for use by the United States, Switzerland, Denmark, the Netherlands and Portugal, the Desert Locust features a wide field of view especially in the inferior arc and on the sides.
Available with the same versions of lenses as the Sawfly, the Desert Locust is available in an Extreme Weather version, which features a fleece lined gasket and thermal lenses, and in a Fan version equipped with a three-speed fan system powered by an AA battery, that provides optimal fog protection in extreme conditions. In December 2010 a similar system was added to the Asian Locust, a version of the Desert Locust specifically designed to match the Asian face morphology.
Looking at future improvements, Revision continues to investigate new laser eye protection technologies, its Special Projects Applied Research Centre has been busy in numerous research topics that vary from new and improved laser dyes and non-linear approaches, combining coatings, dyes and optical limiters which, in combination, are expected to provide broad-range eye protection and high luminous transmittance.
In the context of Britain mentioned above as one of Revision's customers, the manufacturer has also received an order for its new Bullet Ant goggles which together with the Sawflys amount to a [pounds sterling]3.4 million deal. The Bullet Ant is equipped with interchangeable high performance anti-fog and anti-scratch Ocumax-coated lenses and provides ballistic protection against medium-energy fragmentation, sand, wind and dust. Like the Sawfly, the goggle can accommodate prescription lenses through the use of the Rx Carrier device.
ESS (Eye Safety Systems), which in late 2006 became part of Oakley, itself part of the Luxottica Group, provides its Ice (Interchangeable Component Eye-shields) in the Ice-2 and Ice Naro (smaller and narrow fit) to US forces and numerous others. They feature 2.4-mm polycarbonate high impact-lenses in clear and smoke-gray versions, although high-definition yellow lenses as well as rose copper lenses are also available.
The British Forces in Iraq and Afghanistan adopted these spectacles known as Ice-3. The latest ESS add-on to the Apel list is the Crossbow, which Advanced Clear Zone Flowcoal treatment eliminates fog and prevents scratches. For soldiers who wear ear cup protection or communication headgear ESS designed the Crossbow Suppressor, which features ultra-thin temple arms to minimise interference with ear protection devices. All these products are compatible with Rx prescription lens inserts.
As for goggles, the company flagship product is the Profile, with 2.8-mm lenses which also accepts Rx inserts and is provided with tear-off lens covers that allow quick full view re-establishment when goggles are splashed by mud. Clear, smoke-gray and high-definition yellow lenses are available, as well as laser protective lenses. While prescription inserts are becoming more and more used, some soldiers still prefer to maintain their prescription eyewear, and ESS produces two models which are authorized to be used over spectacles - Land Ops and Vehicle Ops - both part of the Striker series.
ESS is continuing to work with helmet manufacturers in order to improve goggle/helmet integration, while it is also working on soft facial armour solutions to make them lighter, more breathable and easier to use with weapon sights. Such systems seem to interest the US Marine Corps; however as there is currently no standard, and getting the right configuration is far from an easy task.
Wiley, whose PT-1 and SG-1 are part of the Apel list (respectively in its eyewear and goggle sections), has recently added new products to its portfolio. The Saber Advanced eyewear features 3-mm Selenite polycarbonate lenses that are scratch-resistant and shatterproof, while an Ultra Foam brow bar prevents sweat and debris from reaching the eyes. The snaps can be removed and replaced with a tactical goggle strap when carrying out high-intensity operations. The Saber Advanced goggle is compatible with the Rx carrier.
A series of new eyewear part, of the Black Ops collection, such as the Brick and the PM-17, is also available, while the Slay is expected to arrive soon. Following a US Government paper that indicated how prescription eyewear with acute face form angles (> 12[degrees]) and pantoscopic tilts with measured angles (> 18[degrees]) could induce distortion, headaches and dizziness, Wiley Talon demonstrated that it was able to meet the new stringent requirements thanks to its shield with near vertical pantoscopic tilt.
Smith Optics Elite Division is active in the tactical field, its Aegis eyeshield is available, among others, with polarised grey lenses to reduce reflected glare and to sharpen details. Such lenses are also available for all the company impact sunglasses collection.
In its goggle range. Smith Optics key product is the OTW (Outside The Wire) Rx-compatible system, also available in the Turbo Fan version which features a two-speed fan that silently evacuates moist air from inner lens. The fan is powered by two AAA batteries and is equipped with an auto shut-off system to preserve battery life, its on/off button can easily be operated with gloves and, according to Smith, it moves 50% more air yet is 40% quieter than competing sets.
Markings According to Ansi/lesa Z87-2010 Type of Description Marking for Other information Mark completed device (no replaceable parts) Impact impact rated Z87+ plano impact rated Z87-2+ Rx Non LG113 Z87 Z87-2 impact Lens clear none 493.8 type UV filter U and scale Scale ranges from 2 to 6, number with lenses marked as U6 providing the highest protection from far and near UV visible light L and scale Scale ranges from 1.3 to filter number 10, with lower numbers providing greater light transmission variable tint V special S purpose Use splash/droplet D3 dust D4 fine dust D5
In the goggles field, Arena produces two models, the Flackjack, which is included in the Apel, and the Mozambik. The latter adopts the company Optiwide lens geometry that, according to Arena, provides 25% greater peripheral vision compared to others, while the Razorback technology manages to deal with fogging, particulates and moisture.
Among the latest products proposed by Bolle of France, although part of the US Bushnell Group, is the Swat eyeglasses with 2.2-mm polycarbonate lenses that provide a V50 of 183 metre/sec for polarised lenses and 196 metre/sec for grey lenses, according to Stanag 2920 testing procedures. As for goggles, its X1000 set feature a double lens, an inside one 1.3 mm thick and an outside lens 3.0 mm thick, which provide a V50 of 272 metre/sec for the grey lens and 275 metre/sec for the clear lens, always to Nato Stanag 2920 testing methods.
Italy ranks amongst the major producers of eye protection frames. Apart from the Luxottica Group, which controls ESS through Oakley, it is thus not a surprise to find two medium-small Italian companies present on the military market. Ars Optical developed its Arsenik Tacti-caleyes series, which includes eyewear and goggles specifically aimed at the military market.
At DSEi 2011 the company will launch its new Space One model, with 2.2-mm polycarbonate high-impact lenses with adjustable nose pad and temple tips, and which weighs only 25.2 grams. As for goggles, the latest add-on is the Eagle, which is equipped with 2.8 to 3-mm thick Spektra Defence lenses made of polycarbonate treated with the Spektra anti-fog technology. Lenses are available in clear and grey versions, laser protective lenses being available on request, as well as Rx inserts for prescription lenses.
Lateral buckles prevent the rubber band to disfigure the lenses when a helmet is used, thus avoiding distortion, while the goggle is also fitted with a removable nose protection. Ars Optical products are in use with Italian Army units, and a new goggle is under development for special forces, as well as with numerous military and police foreign units.
Rudy Project developed the Guardyan, a modular system that transforms a sunglass into a goggle by replacing normal temples with a rubber band strap thanks to a quick lock system, adding a foam shield interface to keep out sand and dust. The main difference compared to the other products described in this article is that Rudy Project chose ImpactX NXT-based lenses instead of polycarbonate ones, the Guardyan being proposed with grey or photochromic lenses.
The same type of materiel is also used in the company-developed Kalybro tactical goggles; provided with hinged buckles for adapting the goggle to helmet and non-helmet use. The Kalybro is proposed with transparent and smoke black lenses, a laser protective lens is available on request.