Development of a Sun Protection Factor for contact lenses (CL-SPF).

Summary

Using standardized SPF methods, spectrophotometry, ray tracing, and in vitro cell assays, the authors propose a contact lens SPF (CL-SPF) that maps lens UV-block performance to familiar SPF categories. Class 1 UV-blocking lenses reached CL-SPF ~60–66 (SPF 50+ equivalent), while non-blocking lenses offered CL-SPF ~1–2. Geometry-dependent sunglass gaps and higher conjunctival UV susceptibility underscore that lenses protect mainly the cornea.

Key Findings

• Measured UV transmission of 15 contact lenses and 3 spectacle materials; derived CL-SPF using standard in vitro SPF methodology.
• Non-UV-blocking lenses: CL-SPF 1.0–2.0; Class 2 blockers: 12.3–24.8 (≈SPF15); Class 1 blockers: 59.6–66.2 (≈SPF50+).
• Ray tracing showed sunglasses’ ocular protection varies with solar angle and head orientation; average 76%–89% light reduction depending on tint.
• In vitro assays indicate ocular surface cell damage profile similar to skin, with conjunctival cells more UV-susceptible.

Clinical Implications

Eye care professionals can use CL-SPF to communicate UV protection, recommend Class 1 UV-blocking lenses for high-risk patients, and emphasize that contact lenses do not protect exposed conjunctiva/sclera—necessitating sunglasses and hats.

Limitations

• In vitro and modeling study without clinical UV exposure outcomes.
• Limited product set and lab conditions may not capture real-world wear environments.

Future Directions

Prospective studies linking CL-SPF categories to clinical photoprotection outcomes and development of standardized labeling across manufacturers; evaluation of combined strategies (CLs + sunglasses/hats).