Ultraviolet Rays

Receiving the right amount of light is critical to good vision, but exposure to the wrong type of light can result in serious long-term problems. Excessive exposure to ultraviolet (UV) wavelengths can cause eye conditions ranging from corneal burns (photokeratitis), growths on the conjunctiva (pterygium) and cataracts. UV is invisible, but that only makes it more harmful.

What is UV Radiation?

Ultraviolet radiation is a part of the overall electromagnetic spectrum and is produced by sunlight, tungsten lamps, welding arcs, and certain types of fluorescent lights. It is classified into three categories: UVA, UVB, and UVC.

Fortunately, UVC (190nm to 280nm) wavelengths are absorbed by the ozone layer of the earth. These short, high-energy radiations can cause mutations in plants and animals. UVB wavelengths (280nm to 315nm) are also considered higher energy wavelengths and can cause sunburns, skin blistering, and skin cancer. This range of UV is why you wear sun block on a sunny day. The upper portion of this spectrum (from 300nm to 315nm) enters and affects the eye. UVA (315nm to 380nm) is the portion of the UV spectrum that is considered most harmful to the human eye because it is totally absorbed by the eye's crystalline lens.

Since the cornea transmits UV wavelengths from 300nm to 400nm, spectacle lenses should absorb these wavelengths for the patient to be protected from ultra-violet radiations. Armed with all the information on harmful UV, lens manufacturers have developed lenses made of materials that absorb these wavelengths without the need for added UV treatments. Remember, the American National Standards Institute (ANSI) requires that lenses classified as UV absorbing block 99.8% of UVB and 70% UVA.

Ultra-violet radiation may be harmful to the human eye, but with all the lens material options available today that absorb it, patients can easily get the protection they need simply by getting the appropriate lens recommendation. The right sunglasses protect the eyes from these damaging rays while still looking stylish and fashionable.