“High index” is a term used to refer to any of a number of plastic lens materials that can do the same job as the more common CR-39 plastic material used for the majority of clear prescription lenses, only they are lighter and thinner. High-index lenses owe their lower profile to the fact that they have a higher refractive index that enables them to bend light more efficiently than materials with a lower refractive index. Because the index of refraction determines lens thickness, high-index lenses are thinner and weigh less than materials with a lower index of refraction. As a result, eyeglass wearers with higher prescriptions (in particular) stand to benefit most from high-index lenses’ greater comfort.
You probably remember older people in your life who wore thick eyeglass lenses. Eyewear has changed dramatically over the past decade. Today’s thin, lightweight lenses help people see near, far, and in-between without compromising their appearance. At DR. DONALD B. KNAPP, OPTOMETRIST, our staff will help you choose from a variety of lenses that will best suit your lifestyle and visual needs. Please call us at (315) 866-3751 to schedule an eye exam, or visit us at 107 N. Prospect St., Herkimer, to browse through our display of frames.
P.S. High-index lenses with a refractive index of 1.67 are about 50% thinner than their CR-39 counterparts.