The idea behind this is to do with how my brain reacts to different frequencies of light, and using this to improve my sleep patterns. Apparently people with delayed sleep phase syndrome are often unusually sensitive to blue light (and UV). Computer monitors and TVs give out enough blue light that we can sit in front of them all night without getting sleepy (a thing I am only too familiar with). The solution to this is either a) don't use a computer or TV near bedtime (argh!), or b) use yellow lenses to block out the UV that prevents your brain from making adequate quantities of melatonin.
I've no idea whether it will work, but anything is worth a try.