LG-011 & LG-011N IPL Glasses spectral OD Curve. Wavelength is shown across the X axis and the Optical density (OD) is on the Y axis. The optical density number represents the number of zero's the eyewear attenuates the light for a given wavelength. For example the LG-011/LG-011N spectral OD curve shows an optical density of greater than OD 1 from 200nm to 1100nm which is the equivalent of least 10 times attenuation of the light over this broad wavelength band.