The lenses you choose for your prescription eyeglasses — even more than frames — often will determine how happy you are with your eyewear.
When buying eyeglasses, the frame you choose is important to both your appearance and your comfort when wearing glasses. But the eyeglass lenses you choose influence four factors: appearance, comfort, vision and safety.
A common mistake people often make when buying eyeglasses is not spending enough time considering their choices of eyeglass lens materials, designs and lenses coatings.
EYEGLASS LENS MATERIALS - FEATURES & BENEFITS
In the early days of vision correction, all eyeglass lenses were made of glass. Although glass lenses offer exceptional optics, they are heavy and can break easily, potentially causing serious harm to the eye or even loss of an eye. For these reasons, glass lenses are no longer widely used for eyeglasses.
In 1947, The lenses were made of a plastic polymer called CR-39, an abbreviation for "Columbia Resin 39," because it was the 39th formulation of a thermal-cured plastic developed by PPG Industries in the early 1940s.Because of its light weight (about half the weight of glass), low cost and excellent optical qualities, CR-39 plastic remains a popular material for eyeglass lenses even today.
In the early 1970s, Gentex Corporation introduced the first polycarbonate lenses for safety glasses. Later that decade and in the 1980s, polycarbonate lenses became increasing popular and remain so today.
HIGH-INDEX PLASTIC LENSES
In the past 20 years, in response to the demand for thinner, lighter eyeglasses, a number of lens manufacturers have introduced high-index plastic lenses. These lenses are thinner and lighter than CR-39 plastic lenses because they have a higher index of refraction.