So much stress is put on being thin. This isn’t limited to the season’s newest looks on the runway but thin and lightweight is also a trend in eye wear.

Ultra thin lenses patient’s desire are actually referred to as "high index lenses" in the optical field. The label refers to the index of refraction. This is the measurement of how light rays slow down in various materials when compared to their speed in air.

Generally, the higher the number, the thinner the lens. For instance, if a lens has an index of refraction of 1.67, then light is moving 0.598 times the speed in air. The higher numbers indicate that light is moving more quickly through the lens. Every lens material has an index of refraction. Along with high index there is also mid index, and ultra high or hyper index lenses. The corresponding numbers look like this. Remember the higher the index the thinner the lens.

Normal Index: 1.48-1.54
Mid Index: 1.54-1.64
High Index: 1.64-1.74
Ultra High Index: 1.74 and above

In the United States, high index lenses are predominantly made from plastic materials. High index lenses tend to have a lower specific gravity than their traditional glass and plastic counterparts. Translated, these lenses are less dense. Other aspects, such as lens center thickness and frame choice will also impact the finished product. The advantage of high indices is that a lens can be created using less material, therefore having less bulk and weight.

Lenses with higher indices also reflect more light than standard plastic and glass. Because of this, anti-reflective coatings are especially important. The additional reflections will be distracting in day to day activities such as night driving and computer use. Anti-reflective coatings add to the overall aesthetics of the lens by eliminating these reflections in photographs and in person. In fact, most high end high index lenses include anti-reflective coatings.

Those with stronger correction (prescriptions) will benefit from the high and ultra high index lenses. If you happen to know your prescription here are a couple of guidelines to think about. Patients with 4.00 D of correction are good candidates for high index, while those with 7.00 D and up would be better suited for higher indices (1.70 and up). Patients who choose larger frame styles or wrap styles should also consider a higher index lens.

High index material is only one factor that can make a pair of glasses not only sleek and attractive but very comfortable. We invite you to visit our Optical Galleries in Stillwater and Pawnee to learn more about various elements in choosing the correct frame and pair of lenses for you. You are welcome to call with questions in Stillwater at 405-372-1715 or Pawnee at 918-762-2573.