The Eye Protection Factor (EPF) is a scientifically applied solar rating designed to help people compare the efficiency of sunglasses in protecting the eyes from the harmful effects of radiation. EPF is to non-prescription sunglasses what the Sun Protection Factor (SPF) is to sunscreen. The EPF rating is based on frame coverage, ultra-violet (UV) protection, blue light protection and infrared protection, or the ability to shield the eyes from heat. The final EPF rating is a result of averaging the scores of these four factors known by the acronym FUBI:
- Frame coverage
- UV protection
- Blue light protection
- Infrared protection
Frame coverage is an important factor, as light that can reach the eye without passing through the lenses increases exposure. UV rays can cause sunburn and skin cancer, but they can also burn the eyes, resulting in cataracts and other visual problems. Recent research indicates that blue light, or high energy visible (HEV) light, might contribute to macular degeneration, or loss of vision detail. Protection from infrared was included as part of the EPF rating because the eye purportedly processes lightwaves differently if the surface of the eye increases in temperature. This isn't usually an issue unless an individual works in close proximity to a heat source, such as a blower's torch.
In averaging the overall EPF rating (~70-100), more weight is given to UV protection than to blue light protection, as UV rays are more damaging. Accordingly, the blue light rating carries more weight than the infrared rating. Sunglasses that have a final EPF rating in the mid to upper nineties have scored well.
The FUBI EPF website lists tested sunglasses along with their EPF scores. Though voluntary, some hope this standard becomes as widely adopted as the SPF standard. The most recent non-prescription sunglass standard to be adopted in the US was the American National Standards Institute (ANSI) Z80.3-2001. This 2001 standard does not require sunglasses to quantify how much UV light is blocked, nor does it require a test for transmittance of blue light. It also does not take frame coverage into consideration.
Sunglasses made in accordance with ANSI Z80.3-2001 are not necessarily adequate, unless they significantly exceed it. The EPF rating provides more information to consumers, allowing wiser choices to be made based on quantitative scientific testing methods.