Without getting into too complicated physics, blue light rays is the blue end of spectrum that have shorter wavelengths that generally defined as visible light ranging from 380 to 500 nm, visible blue light has both benefits and dangers.

Blue light is everywhere, as sunlight, fluorescent light, LED light, display screens of flat TV, smart phone, tablets and laptop. Our eye is not very good at blocking blue light.
Anterior structures of our eye blocking UV rays from reaching the retina but virtually all visible blue light passes through the cornea and lens and reaches the retina.

Hence, blue light exposure may increase the risk of macular degeneration and cause eye strain.

Research has shown that lenses that block blue light besides reduce the risk of macular degeneration and eye strain, it also increase contrast significantly.

Therefore, may increase comfort when you’re viewing digital devices for extended periods of time.