Spectral Evaluation of Eyeglass Blocking Efficiency of Ultraviolet/High-energy Visible Blue Light for Ocular Protection

Abstract

Significance: We investigated, for safety and awareness, ultraviolet and high-energy violet light-blocking protection provided by assorted types of eyewear. Ultraviolet and high-energy violet light-filtering efficiency varied and did not correlate with price or advertised claims. Standardization of methods and specifications for lens spectral transmission evaluation is recommended.

Purpose: Studies have linked exposure of high-energy visible blue light to effect and damage on retinal epithelial cells, photoreceptors, and ganglion cells. "Blue light" is more accurately differentiated into "high-energy visible blue-violet light" and "circadian rhythm blue-turquoise light." This study measured and compared spectral transmission of ultraviolet and high-energy violet light of low-, medium-, and high-priced sunglasses.

Methods: Sunglasses and lens blanks were obtained from the University of Texas Medical Branch Optical Shop and vendors. Groups were based on promotional, retail, designer sunglasses, or "blue blocker" lenses. The percent transmittance of ultraviolet/visible spectral scans (800 to 350 nm) was measured using an Agilent Cary 50 spectrophotometer. High-energy violet/blue light was defined as 400 to 450 nm.

Results: Promotional sunglasses (tinted polycarbonate) blocked 100% ultraviolet and 67 to 99.8% high-energy violet blue light. Retail sunglasses filtered out 95 to 100% ultraviolet A and 67% high-energy violet light. The tested designer sunglasses varied widely in their optical transmissibility with respect to their ultraviolet A and high-energy violet light-blocking properties, with some not blocking ultraviolet A. Clear and colorless Kodak Total Blue provided maximal high-energy violet protection, whereas clear Essilor Crizal Prevencia provided less high-energy violet blocking between 400 and 450 nm.

Conclusions: The ultraviolet and high-energy violet (400 to 450 nm) light-filtering efficiency varied between sunglasses and clear lenses and did not correlate with price or advertised claims. Standardization of methods and specifications for lens spectral transmission evaluation is recommended.

FIGURE 1

Ultraviolet/visible spectrophotometric scans comparing the percent transmission of group 1 (low-cost promotional sunglasses). The average of the five scans is shown in black. The wavelengths, 400 to 450 nm, are high-energy violet light that presents the greatest risk to ocular tissue. This spectral range is emphasized as a shaded area.

FIGURE 2

Ultraviolet/visible spectrophotometric scans comparing the percent transmission of group 2 (medium-cost retail sunglasses). The average of group 1 (low-cost promotional sunglasses), shown in black, is added for comparison. The wavelengths, 400 to 450 nm, are high-energy violet light that presents the greatest risk to ocular tissue. This spectral range is emphasized as a shaded area.

FIGURE 3

Ultraviolet/visible spectrophotometric scans comparing the percent transmission of group 3 (high-cost designer sunglasses). The average of group 1 (low-cost promotional sunglasses), shown in black, is added for comparison. The wavelengths, 400 to 450 nm, are high-energy violet light that presents the greatest risk to ocular tissue. This spectral range is emphasized as a shaded area.

FIGURE 4

Ultraviolet/visible spectrophotometric scans comparing the percent transmission of group 4 (lens blanks and demo lenses). The wavelengths, 400 to 450 nm, are high-energy violet light that presents the greatest risk to ocular tissue. This spectral range is emphasized as a shaded area.

FIGURE 5

Ultraviolet/visible spectrophotometric scans comparing the percent transmission of group 5 (blue blocker lenses). The wavelengths, 400 to 450 nm, are high-energy violet light that presents the greatest risk to ocular tissue. This spectral range is emphasized as a shaded area.

FIGURE 6

Ultraviolet/visible spectrophotometric scans comparing the percent transmission of group 6 (clear, colorless lenses). The wavelengths, 400 to 450 nm, are high-energy violet light that presents the greatest risk to ocular tissue. This spectral range is emphasized as a shaded area.

FIGURE 7

Eye sensitivity function. Photopic eye sensitivity function has a maximal sensitivity in the green spectral range at 555 nm. The inset shows the blue light region, 400 to 480 nm. Drawn from Vos.