Why create the E-SPF ?
Why create a new UV protection index for eyewear?
The E-SPF index goes one step further than existing labels by integrating for the first time UV protection provided by both sides of a lens.
The commonly used “100% UVA/UVB” label does not provide full information on the overall UV protection of a lens*. Indeed it doesn’t take into account UV radiations reflected on the back of a lens, which can represent up to 50% of all UV received into the eye**.
* Existing mention “100% UV protection” refers to the lens’ UV cut rate for the transmission of UVA and UVB hitting the front side of the lens. This mention remains valid. Yet it does not integrate backside UV reflection, which can represent up to 50% of global UV exposure.
** Backside UV reflection importance has been recently emphasized (K.Citek 2008)