Editing Visible spectrum (section)

===Ocular transmission===
[[File:Lens Cornea Transmission.png|thumb|upright=1.5|Cumulative [[absorption spectroscopy|transmission spectra]] of light as it passes through the ocular media, namely after the [[cornea]] (blue), before the [[Lens (vertebrate anatomy)|lens]] (red), after the lens (gray) and before the [[retina]] (orange). The solid lines are for a 4.5 year old eye. The dashed orange line is for a 53 year old eye, and dotted for a 75 year old eye, indicating the effect of lens yellowing.)]]
Before reaching the [[retina]], light must first transmit through the [[cornea]] and [[Lens (vertebrate anatomy)|lens]]. UVB light (<&nbsp;315&nbsp;nm) is filtered mostly by the cornea, and UVA light (315–400&nbsp;nm) is filtered mostly by the lens.<ref name="Boettner-1962">{{cite journal |last1=Boettner |first1=Edward A. |last2=Wolter |first2=J. Reimer |title=Transmission of Ocular Media |journal=Investigative Ophthalmology & Visual Science |date=December 1962 |volume=1 |page=776-783}}</ref> The lens also yellows with age, attenuating transmission most strongly at the blue part of the spectrum.<ref name="Boettner-1962"/> This can cause [[xanthopsia]] as well as a slight truncation of the short-wave (blue) limit of the visible spectrum. Subjects with [[aphakia]] are missing a lens, so UVA light can reach the retina and excite the visual opsins; this expands the visible range and may also lead to [[cyanopsia]].