Prescription Safety Eyewear: Are you protected?

Polycarbonate versus CR39 plastic lenses

With 1 in 4 people requiring prescription eyewear, choosing the right provider for your safety prescription glasses is key. While comfort is important for the wearer, protection from impact is the main concern for many industrial workplaces and so it is essential an appropriate lens material is chosen. The choice of safety glasses should ensure all colleagues are receiving the same level of protection, prescription lenses or not.

What difference does it make during an impact?

Link to impact video for different lens materials

uvex provide a choice of metal, plastic and wraparound frame styles in single vision, bi-focal or varifocal lenses. These lenses are manufactured from polycarbonate for its exceptional impact resistance. Polycarbonate lenses conform to EN166 F and are thinner and lighter than other materials and naturally block out 100% of the sun’s UV rays.

Polycarbonate (PC)

  • Organic material with very high breaking strength
  • Inherently soft allowing it to absorb impacts, ideal for safety eyewear
  • Mechanical strength class "F" (45 m/sec)
  • About 20-25% thinner than plastic or glass lenses
  • Requires scratch-resistant coating for durability
  • Only limited resistance to chemicals and therefore not suited in combination with frameless safety spectacles

CR39 (Plastic)

  • Lightweight organic material
  • Very good optical performance even for high prescriptions
  • Suitable for working with chemicals and paints / varnishes
  • Mechanical strength class "S" (falling ball test)
  • Good scratch resistance due to hard layer (optional)
  • The middle of the lens should always be thicker in order to meet the requirements for tensile strength

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Polycarbonate Lens Impact Test

An alternative material to polycarbonate is CR39 (Columbia Resin 39), a plastic polymer commonly used in the manufacture of eyeglass lenses. Unlike polycarbonate, CR39 requires a UV coating to be added to protect eyes from the sun’s harmful rays. A UV filter is extremely important, especially if you or your employees work outside.

Although commonly used by high street opticians in prescription safety eyewear, CR39 only offers increased robustness conforming to EN 166S similar to that of toughened glass. Many high street prescription safety lens ranges start with CR39 and only ‘upgrade’ to polycarbonate upon request. This is not common knowledge and many wearers assume they are protected just like their peers.

CR39 Lens Impact Test

It is important to note that CR39 is ideal for everyday glasses and Visual Display Users (VDU) but it's not suitable for workplaces where impact poses a risk.

For uvex safety is paramount. Ensure your prescription safety glasses will perform should the unthinkable happen by checking the lens on your glasses to see what markings it has. This information will be either at the top of the lens or on the side. Look for the letters S or F; if you can see an S your glasses are likely to be CR39.

Check your prescription eyewear

Safety prescription glass lenses will have markings to:

  1. identify the manufacturer (in uvex’s case W)
  2. state the optical quality e.g. a 1, and 
  3. the impact strength e.g. S or F

This information will be either at the top of the lens or on the side (see diagram). Look for the letters S or F: if you can see an S your glasses are either CR39 or toughened glass, if it is F then they are polycarbonate. For industrial workplaces with a risk of impact, polycarbonate lenses should be selected.

This information will not be visible on VDU/office spectacle lenses.

Our top tips:

✔ Establish the requirements of the prescription wearer and the hazards they are exposed to
✔ Dispensing opticians serve as the first point of contact for selecting eyewear and rectifying problems
✔ Choose an eyewear manufacturer with nationwide coverage
✔ High street prescription safety offers often start with CR39 and only ‘upgrade’ to polycarbonate upon request
✔ If you buy from a high street optician, don't assume the glasses have the same impact protection as safety eyewear users
✔ Ensure you explain to the optician the hazards you are exposed to at work
✔ Ensure you know which lens material your glasses will be made from

Next steps

If you have any questions or concerns about the material used for your prescription safety lenses, contact our prescription department who will be happy to help.

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