The recent influx of contact lenses containing ultraviolet (UV) filters has prompted some patients to inquire about using these as protection after PUVA therapy, rather than coated prescription glasses, sunglasses or UV opaque protective goggles. But as Suliman Otman, M.D., M.S., a clinical research fellow at the Welsh Institute of Dermatology at Cardiff University, England, discovered, UV-blocking contact lenses are not suitable eye protection for people receiving Psoralen in combination with UVA light.
For the general population, eye protection from damaging UV light is important, but for PUVA patients, additional protection from UVA during the first 12 to 24 hours after treatment is essential to prevent cataract formation from solar UV.
"There is a surprisingly wide variation between lenses, with a range of UVA protection factors from 2.06 to 159.48," Dr. Otman says. And to compound the quandary, he adds, "You can't adequately judge (the product) from the package information. Today's options make it difficult to choose."
Dr. Otman tested the use of 30 different UV-blocking contact lenses in 120 PUVA patients over a three-year period. Specifically, he studied two samples of each contact lens and measured each twice - once with the concave surface facing up and once with the convex surface facing up. He measured the transmission at 5 nm intervals between 290 nm and 400 nm, using the SPF 290 (Optometrics), which consists of a filtered xenon arc lamp, sample holder, integrating sphere, monochromator and photomultiplier detection. From the individual monochromatic protection factors, he measured across the UV spectrum and calculated the average UVA protection factor, as well as the sun protection factor (SPF). From this data, he calculated the various protection factor parameters.
"Surprisingly, we found all of the contact lenses showed some lessening of some parts of the UV spectrum between 290 nm and 400 nm," he says. In addition, the shapes of the monochromatic protection spectra - which illustrate the magnitude of protection (MPF) at each ultraviolet wavelength - were very dissimilar.
Some provide protection Dr. Otman also found that FreshLook lenses (CIBA Vision) maintained UVA protection factors of 20 or more even at the longest wavelengths, while still providing protection factors of 200 or more at narrow-band UVB wavelengths.
These may be useful in eye protection for treating vitiligo on the face with eyelid movement, as well as for PUVA patients who already wear contact lenses, Dr. Otman notes. However, these lenses provide protection for only the cornea and lens, leaving the eyelids uncovered.
Only two lenses showed UV-blocking characteristics that meet the suggested limits for sunglasses used for patients on systemic PUVA, and both use phemfilcon A as the hydropolymer. A lens using lidofilcon hydropolymer had less protection, but significantly more than the other two lenses tested.
"There are many different hydropolymer materials used in contact lenses, and each has very different UV filtering properties," Dr. Otman says. "There seems to be no way for either wearers or clinicians to determine the UV protection of any particular make or model of contact lens.
"It is important for dermatologists to realize that the UV-protective claims for many contact lenses are not based on a single, agreed standard such as the 'UV 400' label scheme," he says. While there are now contact lenses with UV protection that equal good UV-protective sunglasses, they do not protect the eye beyond the pupil, according to Dr. Otman. Still, he says, "They would provide better retinal protection than many open-style sunglasses at specific UV wavelengths."
His conclusion is simple: UV-blocking contact lenses are not suitable eye protection for PUVA patients.