Not All Vision Devices Are “20/20”
Vision Safety and Full-Face Respirator Masks
Imagine first responders, fire fighters, law enforcement officers, hazmat team members, or any industrial or chemical workers responding to an emergency or precarious job situation. They are wearing protective clothing; they are on the scene; and then they don their full-face respirator or gas mask. Now imagine that one of the first responders requires glasses. The respirator mask has the responder’s prescription spectacle kit installed inside. Unfortunately, once the device is in place, the responder sees images that are blurry and wavy. His eyesight is impaired. His performance is compromised; perhaps his life is even at risk.

AWARENESS AMONG INDUSTRIAL HYGIENISTS According to OSHA, 5 million workers in the U.S. are required to wear respirators in over one million workplaces. Respirators protect workers against all sorts of hazardous and harmful elements including gases, dusts, smoke, vapors, sprays and other toxins. Many of these respirators include the full-face respirator mask. For workers who require corrective eyewear, prescription spectacle kit inserts must be specially designed, with specially engineered optical frames, to fit and function inside the mask. The prescription insert may not just be an option but also a vital necessity.
However, not all prescription inserts are created equal. If certain optical considerations are not applied, then temporary poor, unstable vision results. Many of the IH professionals I have worked with over two decades have been unaware of this issue. They sent their worker to an eye care professional with a spectacle kit frame in-hand to have lenses placed in them. Until they understood the optical variances between regular prescription glasses and prescription inserts, the differences never crossed their mind. Most safety professionals, not just IH professionals, hold the same misconception. In many cases, the worker’s performance can be affected simply due to poor vision.
JOHN A. STEWART is vice president of SafeVision LLC in St. Louis, Mo. He can be reached at Send feedback on this article to
COMPLEX, HIGHER PRESCRIPTIONS Workers with low to moderate prescriptions are not the primary concern. The ones at greater risk are those with more complex, higher prescriptions. According to the Vision Council of America, approximately 75 percent of adults use some sort of vision correction. Of those, about 65 percent wear eyeglasses, of which close to 45 percent have higher-than-normal, complex prescriptions.
Since many eye care professionals rarely deal with spectacle kit inserts, they become stumped as to why the patient is having difficulty seeing out of their mask given that the lenses are an exact match to the wearer’s eyewear prescription.
To ensure the safety of the worker, IH and safety professionals should learn the differences between normal prescription glasses and spectacle kit inserts.
First, prescription spectacle kit inserts are designed to fit inside the full-face respirator mask, without the aid of normal earpieces (temples). This is important because normal eyewear earpieces will break the seal on the rubber portion of the mask, allowing toxic fumes, chemicals, or smoke to get inside. To pass fit-testing, spectacle kit inserts must be designed to suspend inside the mask without the aid of normal earpieces.
The challenge is not necessarily with the design of the mask but with the prescription lenses. Since the spectacle kit sits farther away from the eye than normal glasses, and since most prescription eyewear is prescribed and fabricated for normal eyewear, the “vertex” can become the nemesis. Vertex is the distance the lens sits from the eye. Those with a complex or high prescription—45 percent of the eyeglass-wearing population, according to The Vision Council—can simply move the glasses away from their eyes and notice a significant difference in their vision.
This change in vision is due to the worker’s prescription, which is refracted for normal eyewear and vertex distances, generally 9–13 mm away from the eye. A typical spectacle-kit insert sits farther away from the eye, minimally 15–19 mm. If adjustments aren’t made for the change in distance, the wearer will experience significant vision issues for at least 15 to 30 minutes, a time period that can be crucial for first responders.
A second consideration is the base curve of the insert. If it deviates significantly from the curvature of the face shield, distortion may occur. The prescription lens base curve can be adjusted to more closely match the curvature of the facemask, which reduces distortion.
Third, workers with bifocals require special consideration. The internal design of each full-face mask and its nose cup will determine the type and positioning of the bifocal. Many eyewear professionals don’t have the internal mask measurements. Instead, they apply standard bifocal measurements; some even choose what are known as “progressive no-lines”—a type of lens intended to provide smooth transitions between near, middle, and far distances. The bifocal then becomes inefficient since the nose cup interrupts most of its functionality. Each mask has its own bifocal positioning measurements.
The American National Standards Institute has established optical guidelines to help IH professionals and safety directors improve worker safety with spectacle kits (ANSI Z80.1-2015, Standards for Principle Optical and Geometric Tolerance). These guidelines can help safety supervisors ensure that their workers’ masks are both functional and compliant.
Another standard (ANSI Z87.1-2015, Occupational and Educational Personal Eye and Face Protection Devices) recently addressed safety concerns related to prescription lens carriers. According to ANSI 787.1-2015 Section 6.3.3, prescription spectacle kits behind Plano (non-prescription) protectors “shall meet the same impact requirements as other Rx devices if the Plano protector, in this case full face respirator face shields, is impact rated.”
The carrier’s lenses (spectacle kit inserts) must be marked with the manufacturer’s logo only. No other Z87 markings are required.
Advances in lens technology include new super-thin high-ballistic lenses, which are ideal for prescription inserts. These lenses are thinner than traditional safety lenses, lighter, stronger, and safer, with much improved optics. FULL-VISION FUNCTIONALITY FOR EMERGENCY RESPONDERS If proper measurements are taken at the outset to manufacture the proper insert spectacle, emergency responders can avoid the 30-minute period of vision correction.
Working with spectacle kits is a separate specialty. IH professionals who currently have a relationship with a safety eyewear firm may wish to ask about their expertise in this area or seek out a company with a history of providing this service. Many companies use their safety eyewear provider for standard prescription safety glasses but call on a specialist for prescription spectacle kits.
Ordering the proper prescription eyewear for spectacle kits doesn’t require the employee to see an eye care professional. All the spectacle kit provider needs is a copy of the employee’s prescription with pupil distance measurement (PD).
The right provider will have all the necessary internal dimensions and measurements for each full-face mask. They can provide a complete pair of compliant prescription spectacle kit inserts ready for use without the temporary vision adjustment period. And they can help first responders, chemical workers, and hazmat employees with high or complex vision issues immediately perform all job requirements, which might make the difference between success and tragedy.
RESOURCES 20/20: “The Real Details of Vertex, Tilt, and Wrap” (March 2015).
The Vision Council: “US Optical Overview and Outlook” (PDF, December 2015).