High Index Thin Lenses
August 22, 2014
Modern high index lenses are manufactured with materials making them thinner and lighter than was previously possible. These new lenses provide visual and cosmetic benefits for stronger corrections because they are thinner and flatter than conventional lenses. This greatly reduces the “Coke-bottle” effect associated with thicker, conventional lenses and provides improved clarity across the lens surface, especially in higher lens prescriptions.
Why can high-index lenses be made thinner?
Eyeglass lenses correct vision by bending light as it passes through the lens. Your lens prescription determines the amount that light must be bent to focus correctly on the inside back of your eye (retina) and give you good vision. Nearsighted prescriptions decrease light bending (“-” lenses) and farsighted prescriptions increase light bending (“+” lenses.)
The physics behind these high-index lenses is centered around the “index of refraction.” A lens material with a high index of refraction more strongly bends light so less lens material is needed to produce a given lens prescription.
The higher the index of refraction, the thinner and lighter a lens will be. Popular lens materials today are those with indexes of 1.60, 1.66, and 1.71. Material with an index of 1.71 is the thinnest material currently on the market and is normally used for moderate to high amounts of nearsightedness or farsightedness.
What are Aspheric Lenses?
The curvature in an Aspheric lens is not constant across the whole lens. The curvature gradually changes from the center of the lens to the edge of the lens. Overall, aspheric lenses have flatter curves. They are thinner and do not appear to “bulge” out of the frame like conventional lenses do. While high-index lenses benefit nearsighted wearers the most, they offer significant advantages to farsighted wearers also.
The distance a prescription lens is positioned in front of the wearer’s eye has cosmetic ramifications. Strong farsighted lenses tend to enlarge the wearer’s eyes, producing a magnified appearance. Strong nearsighted lenses do just the opposite: they minify the wearer’s eyes making them look smaller. To decrease both magnification and minification effects, a lens should be positioned as close to the eye as possible. That is what an aspheric lens does in many cases…resulting in a more pleasing cosmetic effect.
So What Does all this Mean?
High index materials can provide you with significant advantages over traditional plastic or glass lenses such as reduced thickness of the lenses and more resistance to shattering. High index lenses absorb all harmful UV light and can be tinted to any shade or color. When combined with an anti-reflective coating, the result is the best-looking prescription eyeglasses that modern science can provide. The next time you order new eye-wear be sure to ask us about High Index lenses!
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