Retinal light damage is also wavelength-dependent, with green light most effectively causing damage in rod photoreceptors. In other words, the action spectrum for light damage closely approximates the absorption spectrum for rhodopsin.^[1,7,8] (Figure 64.1). However, blue light as well as full-spectrum white light also causes retinal damage by bleaching rhodopsin, albeit less efficiently. Blue light has a shorter wavelength than green light and is therefore more energetic (Planck's relation: E = h/λ, where E = energy, h = the Planck constant, and λ = wavelength). Accordingly, blue light is capable of photoisomerizing free all-trans retinal, the aldehyde form of vitamin A, into the 11-cis stereoisomer required for rhodopsin regeneration.^[9] This reaction may short circuit the normal postrhodopsin-bleaching vitamin A cycle, involving migration of all-trans retinol into the retinal pigment epithelium (RPE) and enzymatic reisomerization to the 11-cis form.^[10]In …