High index lenses made from specialty plastics allow thinner, lighter lenses than traditional glass or plastic. These lenses are geared towards those with very strong prescriptions, both nearsighted and farsighted. Glasses correct vision by bending the light that passes through them. A stronger prescription requires more bending than a weaker one, resulting in a thicker lens. A high index lens is made of denser material than conventional one, bending more light through less thickness, resulting in ultra-thin, lightweight glasses.
When viewing conventional glasses, one can easily see lenses designed to correct nearsightedness. The lenses are thicker at the edges than in the middle. The stronger the prescription, the thicker the edges become.
Most stylish frames are too thin to hide the thick edges of nearsighted lenses. Thick lenses also distort the eyes, making them look unnaturally small. High index lenses eliminate both problems.
Those with extreme farsighted vision have lenses that are thicker in the middle, with thin edges. The thick middle has the opposite effect of a nearsighted lens, making the eyes look unnaturally large. Again, these denser lenses offer a solution.
All lenses are categorized by how much light they can bend using an index of infraction. This index compares lightspeed through air to lightspeed through the lens material. Glass bends light at an index ratio of 1.52, while conventional plastic has an index of 1.50. Lenses with a greater index are considered high index.
There are several plastic materials now available with index ratios between 1.53 and 1.71. The higher the index, the thinner, lighter, and more expensive the lenses. High index glass lenses are also available, with a ratio of 1.90. However, glass lenses are not as light or durable as plastic lenses. In fact, high index glass is actually heavier than standard glass, canceling much of the benefit of the thinner lens.
High index lenses can correct astigmatism and are available as bifocals or trifocals. They look nice in thin, wire, and “frameless” frames. The index that will best suit you is determined by your prescription, but don’t assume a vendor will make the best choice for you. Some suppliers do not sell all types, and you could end up with a lower index lens than is ideal. Ask your optometrist which index is best.
This type of lenses are available from many optical centers. They can make wearing glasses more enjoyable, improve self-image, and restore confidence. They are durable and shatterproof, perfect for children and active adults. After you’ve worn a pair of high index lenses, chances are you’ll never go back to standard glasses again.
