Assessing the sun protection offered by contact lenses

Researchers from Aston University have explored the potential for contact lens companies to provide “a more meaningful metric” of the sun protection provided by contact lenses.

Writing in BMJ Open Ophthalmology, the authors explained that while Sun Protection Factor (SPF) is used to rate the protection provided by sunscreen and some clothes, at present there is no equivalent communication tool for optical correction.

To investigate the feasibility of providing a similar measure within optics, researchers assessed UV transmission through 15 commercially available contact lenses and three spectacle lens materials.

They assigned the contact lenses to three categories: contact lenses without a UV blocker (equivalent to using no sunscreen), contact lenses with a Class 2 UV blocker (comparable to SPF15) and contact lenses with a Class 1 UV blocker (equivalent to SPF50).

The researchers also assessed the cellular damage profile of human corneal and conjunctival cells across the UV range, finding that the death of ocular surface cells has a similar profile to that of skin.

However, the scientists found that conjunctival cells are more prone to UV damage.

“A contact lens will only protect the area of the ocular surface it covers, which is limited to mainly the cornea and internal eye tissues,” the authors noted.

The scientists shared that providing an SPF measure would enable the contact lens industry to provide a “more meaningful metric” of the sun protection offered by their products to consumers.

“The present study shows that CL-SPF is a viable metric to communicate the protection from the transmission of UV that some CLs offer wearers,” the authors concluded.