Recently, the blue/violet wavelengths between 400nm and 500nm have been implicated in the development of macular degeneration. BPI® has developed a simple meter that is designed to check the transmittance of lenses for these wavelengths and provide a figure of merit to use in comparing and producing lenses that protect patients from radiations in this wavelength range.

The BPI® UV & Blue Light Analyzer uses LED light sources centered at 400nm, 430nm, 470nm and 505nm to evaluate lens transmission in these regions. The transmission percentage at each range is displayed along with the Wertheim Protection Factor, a figure of merit based on a comparison of the lens’s photopic transmission with its blocking ability for high-energy (blue/violet) wavelengths.

The meter also has caution indicating LEDs which indicate if the lens transmission is higher than that which would be provided by a linear drop in transmission with wavelength from its Tv value down to zero in the UVA.

Air (no lens) lights all caution LEDs and has a Wertheim Protection Factor of “0”. A lens with high luminous transmission but minimal high energy blue/violet transmission such as BPI® Total Day has a Wertheim Protection Factor of “43”.