The technology of both the e’re fabled Red Ryder BB Gun and traditional eyeglass lenses has thankfully improved dramatically since 1983 when Ralphie famously “shot his eye out!” Unfortunately for Ralphie, his traditional glass lenses shattered from the backfired BB even before he unwittingly stepped on the frames and pulverized them. The glass lenses ultimately did protect Ralphie’s eye from the impact, but just barely!

Today, nearly 42 years later, most eyeglass lenses are made of high-quality plastics, polycarbonates, or acetates (varieties of polymer plastic) with varying degrees of thickness, weight, clarity, impact resistance (the Red Ryder special, if you will!), and a wide variety of other features and technologies including tints, UV protection, light-responsivity, and more.

Indexing the Differences in Eyeglass Materials

Basic eyeglass lenses can be most simply divided into three essential categories: Standard > Mid Index, High Index, and Impact Resistant.

The “index” of each material refers more precisely to the “index of refraction”, or the measure of how light is bent as it passes through the lens material. There are reasons why one material may be better suited to a plastic or wire-rimmed framed, or a rimless or half-rim frame, but more importantly, the material best suited to your needs will be determined by power of your particular prescription, or the Rx power.

Standard to mid index plastics are in turn best suited to Rx powers ranging +1.00/-2.75 and +2.00/-3.75 respectively. Mid index lenses are 15% thinner than standard index lenses and suited to the higher power prescriptions.

High index lenses vary from 20% to even 30% thinner than standard index lenses and range from +3.00/-5.75 to +4.75/-6.75 respectively. High-index lenses are thinner at the edges for nearsightedness and reduced thickness at the center for farsightedness.

Impact-resistant lenses are made from much more durable materials such as polycarbonate or Trivex (a lightweight urethane-based plastic material). Both are designed to absorb shock and impact, making them less likely to crack, chip, or shatter if dropped or inadvertently struck by an errant BB!

While standard and high index plastic lenses provide at least a little protection from impact, they are not generally considered “impact resistant” and are not recommended for uses with high impact potential.

The Incomparable Clarity of Glass Eyeglass Lenses

Glass lenses were the standard for all eyeglass applications since the first eyeglasses were invented. With the advent of plastic lenses, glass lenses have gone out of favor in many respects because of their weight and vulnerability to breakage.

But glass is making a comeback! Glass lenses offer far superior clarity, optics, resilience in extreme temperatures, and scratch-resistance. Improvements in manufacturing technologies means that glass lenses can be flatter and thinner, with high levels of prescription precision. Glass lenses also offer lesser distortion of images due to the inherent nature of glass resulting in reduced eye fatigue and increased comfort.

Glass lenses may be the forebearer and stealing back into fashion, but for now at least, plastic lenses are still the standard bearer. Talk to your eye doctor and optician to determine the best lenses for you!