Blue light travels in shorter wavelengths and with higher energy than other types of light. Its main source is the sun, but can also be emitted by fluorescent lights, LED lights, flat screen LED TVs, smartphones, computer monitors and tablet screens.
Packaged medical devices like contact lenses have expiration dates the same way packaged foods, beverages and other perishable products do. It means they are no longer useful when they are past the date stated on the label. This article discusses what you need to know about expired contact lenses.