Can High Index Lenses be Safety Glasses?

Safety glasses currently feature more options than ever before.

Can High Index Lenses be Safety Glasses?

Various tints, coatings, full prescription capability, and lens options like bifocal and progressives make customization of safety glasses a simple prospect. Attractive, modern frame styles serve fashion as much as practicality; streamlined frameware can be impact resistant and look great at the same time.

Another relatively modern development in the eyewear industry is the advent of high index glasses. Formed from a special composite material in either a glass or plastic format, high index material bends light a bit differently than standard glass or plastic material, a characteristic that allows it to accept deeper prescription curves while using less physical material. The result, especially for those who require a very strong prescription, is lenses that are significantly thinner and often lighter as well.

As with any product, high index lenses feature specific pros and cons. If you’re thinking about switching to them, the list below should be taken into consideration. High index lenses feature:

• The ability to form a high prescription using less physical glass or plastic
• Often lighter than standard plastic or glass (depends upon the prescription and the material used)
• Often are significantly thinner than standard plastic or glass
• Reduced edge size
• Allows for multiple single- and progressive-use designs
• Higher production cost than standard materials
• Potentially more chromatic aberration (Abbe value)
• More brittle and reflective (especially in glass form)

If you use (or plan to use) high index lenses in safety glasses, several of the above items are relevant. Yes, high index lenses can be used in safety frames and will qualify as rated safety glasses, but there are restrictions. For instance, to reach the impact-resistant standard required of the safety lens designation, high index lenses must have a minimum thickness of 3.0mm. Lenses below that level are too brittle to meet safety standards.