Using a single-standard, a research team identified that all 21 soft contact lenses (SCL) they reviewed meet the standards for ultraviolet blocking and visible light-absorbing properties, according to a study published in Optometry and Vision Science. The study also confirmed that back vertex power, which determines lens thickness, affects UV transmissibility.
The open, prospective material study sought to determine the spectral transmittance of UV-A, UV-B, and the visible spectral range of various hydrogel and silicone hydrogel contact lenses with and without UV blockers. Researchers measured UV and visible light transmittance of SCLs using the standard. They analyzed339 SCLs with UV blockers (stenfilcon A, somofilcon A, narafilcon A, senofilcon A, senofilcon C, etafilcon A, nesofilcon A) and 489 lenses without UV blockers (delefilcon A, lotrafilcon A, lotrafilcon B, comfilcon A, balafilcon A, samfilcon A, asmofilcon A, nelfilcon A, omafilcon A, hilafilcon B, ocufilcon D, hioxifilcon A, omafilcon B) with the following back vertex powers: ±1.00, ±2.00, ±3.00, ±4.00, ±6.00, −8.00, −10.00, and −12.00 D. A total of 21 lens brands were investigated in the back vertex power (BVP) range of −12.00 to +6.00 D, and three SCLs were measured per BVP 25 times.
Researchers found that all UV-absorbing labeled test SCLs meet UV protection class 2, with senofilcon A, senofilcon C, and narafilcon A meeting the higher UV protection class 1 level. They discovered a statistically significant difference in UV transmittance (280 to 380 nm) between SCLs with a positive BVP (+1.00 to +6.00 D) and SCLs with a negative BVP (-1.00 to -12.00 D), both without (P =.04) and with UV filters (P =.02).
Study limitations include the measurement of a very narrow 6mm area of corneal diameter.
“Lenses with increased center thickness absorb more UV radiation,” according to the report. “Further studies may use a modified measurement setup with a larger aperture than 10 mm. It would also be worthwhile to examine the UV absorption of the contact lens over the complete corneal area and limbal area because UV radiation may damage inner ocular tissues like the crystalline lens as well as limbal stem cells.”
Kapfelsberger A, Eckstein J, von Ahrentschildt A, Bischoff JD, Marx S, Sickenberger W. Ultraviolet and visible transmittance of soft contact lenses with and without ultraviolet blockers. Optom Vis Sci. 2021;98(11):1270-1278. doi:10.1097/OPX.0000000000001796