MAY 07

Do I Need High Index Lenses?

Every time something innovative and new is invented, there is always the question of who will need it and who won’t. Electric heaters, for instance, incredible as they are for making homes in cold climates affordably warm and cozy are also only useful to people who live in those cold climates. While some innovations are more universally useful than others, when considering investing in something new, it’s always important to ask yourself “Do I need this?”

This is exactly the case with one of the latest developments in eyeglasses technology, high index lenses. Invented in 1983 in an attempt to make shatter-proof glass lens alternatives. While the discovery itself and the methods involved are quite scientific, the effect has been primarily a fashion movement. Most people who have heard about high-index lenses have done so under in the context of finding a sleeker, more attractive style of eyeglasses.

What Are High Index Lenses?

Polycarbonate was the original high index lenses. It is still one of the strongest lens material, safe for children and sports, but the real discovery was what happened when the development team tried to make the lens more dense in order to make it stronger. By creating a more compressed lens plastic, they also increased the index of refraction, which is how quickly light moves through the material. When light changes speed, it also bends a bit changing the image we see, just like how a straw looks different above and below the water level in a glass. The denser a lens is, the higher the index of refraction and the more tightly light bends through it making them more efficient for prescriptions. This is why they’re called high index lenses.

What this means is that the same prescriptions can be created with a much thinner lens. Normal plastic and glass lenses have a natural index of about 1.50. Higher indexes are thinner, with the thinnest plastic lenses available at 1.74 and the thinnest glass lenses available at 1.90.

High Indexes Slimming Down Your Lenses

For everyone who wears glasses, of course, thinner lenses sounds like a good idea. Who doesn’t want to reduce the amount of glass or plastic between them and the rest of the world? Thick lenses can be problematic on a number of levels, not least of which the fact that it makes you feel like a cartoon whose eyes are never seen behind their glasses. Thick lenses don’t just affect your experience, they change how other people see you as well. The thicker the lens, the more your eyes look distorted behind them, that is unless light aberrations and reflection have already made it impossible to see your eyes at all.

High index lenses are the most useful to people who have strong prescriptions resulting in very thick lenses. They can slim down both the thick lens edges of glasses for nearsighted eyes and the bulging central lens for farsighted lenses. The high index makes both thicknesses less necessary as light bends more efficiently through the material.

Are High Indexes About Function or Fashion?

One of the major debates about high index lenses is whether or not they’re more about fashion or function. There is definitely a strong argument for the fashionable side of things. When you are stuck with thick lenses. there are a large variety of frames that either can’t support large lenses or simply look terrible with them. If your personal sense of style involves rimless, wire-framed, or otherwise slender designs, thick lenses often look ridiculous and unattractive. Instead, you have to go with thicker, often plastic frames even if they’re not your preference. With high index lenses, especially with the selection if indexes, you can now choose exactly the right thickness of lens for whatever style of frames you want. If you want rimless or half-rims, you can get lenses just thick enough to hold the invisible support wire. If you like wireframes, you can go practically paper thin as long as you’re willing to take special care not to break your beautifully delicate glasses.

As for function, there are a lot of good things to say about high index lenses. First, they are almost universally sturdier and more damage resistant than standard lenses because they are made of increasingly denser materials. High index lenses need less curvature of the lens, making for a flatter lens, less eye distortion, and clearer peripheral vision as more of the lens is able to accommodate the full prescription. Most plastic high-index lens materials block harmful cataract-causing UV light and are more lightweight than standard lenses of the same prescription, relieving stress on your nose and ears.

How Thin is Each Index of Lens?

To understand whether high index lenses are right for you, it helps to know what each stage of high index means. The numbers are determined by the materials developed at each level. With 1.50 as the standard, the lowest of the high indexes is 1.54 which you can find with a Trivex, which is also the most lightweight material you can find and is sturdy enough for sportswear. These are about 15% thinner than standard lenses.

Next is the original polycarbonate at 1.59 which will give you 20% thinner lenses. Both polycarbonate and Trivex block all UV rays and Polycarbonate is still quite lightweight. Tribrid lenses take it up one step further to 1.60 and are much more impact resistant than most, though they are not universally vailable yet. Finally there are the high-index plastics which have been specially designed to achieve an unusually high index at 1.67, 1.70, and 1.74 respectively. These range from 30-35% thinner. But what does this really mean? 35% doesn’t sound like that much until you actually see the difference and realize how thin the result truly is.

Do You Need High Index Lenses?

Of course, chances are you came to this article wondering if high index lenses were right for you. This depends on a number of factors. High index lenses are the most useful to people with strong prescriptions and naturally thick lenses. Depending on the index you choose, very thick lenses can become normal-width or even fashionably slender. For those with less need for visual correction and therefore thinner lenses under normal circumstances, you can still benefit from high index lenses but may be better choosing one of the mid-high indexes. Otherwise, your lenses might become impractically thin.

Then there’s the question of your own personal style. Slender frames will almost universally look better with high index lenses even if you have a gentle prescription because it will allow the lenses to practically disappear even into thin wire frames. Rimless and half-rim lenses have a minimum thickness so that they can support a wire and frame attachments so while they are great with high index lenses, you may want to work with your optician to choose the correct index for your needed thickness. Of course, if your favorite frames are thick plastic, then you only need an index high enough to fit within the bounds of the frames.

So do you need high index lenses? If you have a strong prescription or prefer the sleekest possible style of eye-wear, then the answer is yes. As for everyone else, as long as you choose an index that suits your frames and prescription, high index lenses are useful for function and fashion so you might really enjoy trying them either way.

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