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James Stuart Wolffsohn, Thomas E Drew, Rachel Walsh, Hannah Bartlett, Anna Sulley; Can a Contact Lens Sun Protection Factor (SPF) be Derived?. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4659.
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To determine whether the sun protection factor (SPF) of soft contact lenses can be appropriately determined using the in-vitro methodology adopted for skin suncream lotion products.
Illumination from a deuterium arc lamp (DT-mini-2-GS, Ocean Optics, Florida USA), with output from 200nm to 1000nm with a spectral profile similar to that of the sun, was passed through soft contact lenses and the change in spectrum measured with a spectrometer with the same spectral range (CCS200, Thorlabs, Germany). The light filtration of the centre of -3.00D powered etafilcon A, nelfilcon A, hilafilcon B, nesofilcon A, narafilcon A, lotrafilcon B, delefilcon A and senofilcon A contact lenses were assessed. The spectral profile reduction was converted to a SPF using the erythema action spectrum and the irradiance of the source at each wavelength compared to monochromatic absorbance of the contact lens over the 280-400nm wavelength range.
Soft contact lenses with minimal ultraviolet (UV) blocking properties (nelfilcon A, lotrafilcon B, delefilcon A and hilafilcon B) were calculated as having an SPF between 1 and 2 (average 1.4 ± 0.4 SPF). Lenses classed as having class 1 (narafilcon, senofilcon) or 2 (etafilcon, nesofilcon) UV blocking according to the American National Standards Institute (ANSI) and International Standard Organisation (ISO), had a significantly higher SPF (p < 0.001) with values greater than 50.
UV blocking contact lenses have a high SPF as assessed by in-vitro methodology developed for skin sunscreen lotions. In addition, Class 1 and Class 2 blocking contact lenses also have UVA blocking properties, which is minimally accounted for when deriving the SPF (principally UVB). Therefore it seems that while skin SPF does provide some relative information regarding the UV blocking properties of contact lenses, it does not take into consideration all of the relevant factors for comprehensive UV eye protection.
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