Information about sunglasses

It is crucial to receive the right amount of light to have good vision, but too much exposure to the wrong type of light just might result in serious long-term problems. When our eyes are exposed to excessive amounts of ultraviolet light (UV) wavelengths can cause eye conditions including corneal burns (photokeratitis), growths on the conjunctiva (pterygium) and cataracts. UV rays are invisible, and that only makes them more harmful.

Ultraviolet radiation, more commonly referred to as “UV Rays,” is a part of the electromagnetic spectrum and is produced by the sun, tungsten lamps, welding arcs, and certain types of fluorescent lights. It consists of three categories: UVA, UVB, and UVC.

Fortunately, UVC (190nm to 280nm) wavelengths are absorbed by the ozone layer so for now we don’t have to worry about them. However, these high-energy radiations can cause mutations in plants and animals. UVB wavelengths (280nm to 315nm) are also higher energy and can cause sunburn, skin blistering, and skin cancer. Since none of us really enjoy any of these things we wear sun block on sunny days. (Right?) The upper portion of this spectrum (from 300nm to 315nm) is where we start to see effects on the eye. UVA (315nm to 380nm) is the section of the spectrum that hurts the most because it is totally absorbed by the eye’s crystalline lens. (Ouch!)

Our corneas transmit UV wavelengths from a range from 300nm to 400nm, so it becomes important to us and especially to our eyes to filter these wavelengths out. That is where lenses come into play. Lucky for us, the American National Standards Institute (ANSI) has mandated that lenses be made with materials that absorb or block at least 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 a good pair of glasses or sunglasses and remembering to wear them.

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