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Vision plays a key role in the performance of many occupations. This is especially crucial for first responders such as firefighters and law enforcement professionals, chemical and hazmat workers, and others who must wear full face respirators and gas masks. Many require prescription inserts in order to see properly, maximize visual performance, and effectively do their job.
New optical requirements and safety values have recently been put in place with regards to these inserts. Many optical professionals, safety personnel, first responders and industrial consultants may not be aware of them. In fact, the performance of many who depend on optimum vision for on-the-job performance can be negatively impacted with ongoing vision issues. The good news is now those issues can be corrected.
Industrial hygienists need to be aware of these new requirements so they can recommend the proper procedures to secure a compliant and functional prescription spectacle kit insert for their workers. The byproducts are improved health, better safety, and an increase in productivity.
Why is this important? According to estimates (https://www.osha.gov/SLTC/respiratoryprotection/) 5 million workers in the U.S. are required to wear respirators in over a million workplaces throughout the United States. Respirators protect workers against all sorts of hazardous and harmful elements including harmful gasses, dust, smoke, vapors, sprays, and other toxins. Many of these respirators include the full-face respirator mask. For those that 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 be just an option but also a vital necessity.
The process of matching the appropriate Rx Spectacle Kit to the users need for optimum visual acuity can be complex. Many optical professionals do not understand this process. It begins when an employee is given a generic spectacle kit frame or insert designed for their mask. They are then instructed to take the insert to their eye care doctor to have their eye glass prescription ground and placed into the frame.
The lenses are made and delivered. The wearer is excited to see how their new Rx spectacle kit will work inside their mask. They insert the frame then don the device. Unfortunately, in too many cases, the first time they try the insert, they experience vision problems.
First time wearers will see images that appear to look wavy. The worker can feel dizzy. As they move their head everything seems to take a distorted form and shape. Complaints often follow to their IH or safety professional.
The IH professional instructs the wearer to go back to their eye care professional to analyze the problem. Their eye doctor looks at the lenses through a lensometer to verify prescription accuracy and verifies other measurements to be on the safe side. The patient is then told that everything seems to be accurate with their Rx inserts. The doctor is puzzled why their patient is experiencing vision problems.
In most cases the doctor tells the patient their eyes will eventually adjust to the lenses. The worker believes he/she was properly fit tested, with the current eye glasses prescription. Yet the inserts do not work well.
This is a common scenario in the eyewear industry. Many corporations, organizations, and municipalities will operate with inserts that are not up-to-par. Since the masks are not worn regularly they believe no adjustments are necessary. However, improper vision can be highly detrimental to first responders and others in high-risk situations.
In order to improve performance, prescription spectacle inserts should be considered a task specific occupational product. This should be in the same genre as specialized lens tinting for radiant light protection, non-conductive safety eyewear, Rx full field-of-vision eyewear for forklift and mobile equipment operators, or any other specialized eyewear engineered for specific occupational tasks.
Attention must be given to the internal design of the masks themselves and how the spectacle kit insert is positioned inside the mask. Understanding that relationship will help the wearer avoid vision problems, especially if the prescription is complex.
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 Tolerances) These guidelines, as they relate to Rx spectacle kits, fall into three categories; vertex distance, lens base curves, and bifocal type and positioning.
Vertex distance. Vertex distance is simply the distance the lens sits from ones eyes. Most prescriptions are based on standard vertex distance as prescribed for wearing normal eye glasses. However, Rx spectacle kit inserts, in most instances, are positioned further away from the eye than normal eyewear. This changes the correction of the prescription. And, depending on the complexity of the correction, or if there is a significant level of astigmatism power, it can require some time for the eyes to fully adjust to this difference.
The American Optometric Association estimates that it could take up to 30 minutes for ones vision to fully adjust to the difference in vertex distance. The vertex compensation calculation is standard ophthalmic knowledge, The Real Details of Vertex, Tilt, and Wrap. (https:www.2020mag.com/ce/ttviewtest.aspx?lessonld=111203). However, if the distance the insert sits from the eyes is unknown inside a given mask, then ones vision is altered until their eyes can adjust.
In many professions, where a full face respirator mask or gas mask in emergency situations is worn, one does not have up to 30 minutes for their vision to adjust. In an occupational or hazmat setting, poor or unstable vision will negatively impact safety and/or productivity.
The manufacturing of lenses to be worn with Rx spectacle kit frames requires a full knowledge of the internal measurements of a respirator mask and spectacle kit positioning. This is necessary to compensate for the difference in vertex distance. A slight adjustment of the prescription will need to occur to offset the vertex distance effect so there is no visual adjustment period. The wearer will be able to quickly obtain full visual functionality and safety.
Lens Base Curves. In many cases it is necessary for the prescription spectacle kit lens to be processed with a curvature closely aligned with the curvature of the masks shield. This will result in less glare and distortion.
Bifocal Type and Positioning. Not all bifocal types will function effectively inside a respirator or gas mask. And, because of the vertex distance issue, as well as the design of the nose piece inside the mask, positioning of the bifocal is critical. Improperly placed or positioned, like normal eyewear, the bifocal could impede vision or be cut off by the nose piece.
Understanding internal measurements, and how each insert is positioned in different full face and gas masks are the keys to hassle free, precise vision for a prescription spectacle kit.
Safety Values. ANSI Z87.1 has recently addressed Rx lens carriers, including Rx spectacle kits behind Plano (non-prescription) protectors shall meet the same impact requirements as other Rx devises if the Plano protector, in this case full face respirator face shields, is impact rated, ANSI/ISEA Z87.1 2015 Section 6.3.3.
The carriers lenses (spectacle kit inserts) must be marked with the manufacturers logo only, and no other Z87 markings are required.
IH and safety professionals should consider the new super-thin high-ballistic lenses which are ideal for Rx inserts. These high-tech safety lenses are thinner than traditional safety lenses, lighter, stronger and safer, with better optics.
Industrial Hygienists can improve their organizations safety and compliance by asking their safety eyewear provider if they understand and apply these new optical and safety requirements.
