The Pros and Cons of High-Index Lenses

When it comes to choosing the perfect prescription eyeglasses, we tend to overlook a crucial element— the lenses, and we just don’t spend a lot of time thinking about them.

After choosing the right lens option, the most flattering frame styles, and our preferred color, we usually breeze through the prescription input and order our prescription glasses without a second thought. But rather than treating our prescription eyeglass lenses as an afterthought, they should be given a decent amount of consideration, especially when choosing the refractive index level.

You may find yourself asking - what exactly is a refractive index level and why does it matter? Should I be choosing a particular kind for my prescription eyeglasses? Is there anything I need to know in order to choose the right lenses to suit my needs? What does it all mean?

To help you answer these questions and more, we’ve put together a breakdown of the different index levels in prescription lenses with a special focus on the pros and cons of high-index lenses, one of our most popular offerings at Azimuth. Keep reading to learn more.

What are Refractive Index Levels?

In simpler terms, refractive index levels can be thought of as determining the thickness or thinness of your eyeglass lenses. A higher index level results in thinner lenses, while a lower index level leads to thicker lenses. These levels also refer to how efficiently lenses bend light, which is crucial for our prescription eyeglasses to effectively correct vision problems. 

Higher-index refractive lenses excel at bending light more effectively, making them capable of correcting a wide range of prescription strengths, including those that are on the heavier end of the spectrum. On the other hand, lower index lenses are only able to handle mild prescription ranges due to their less effective performance in bending light.

What’s the Difference Between Index Levels?

Now that we’ve laid out the basics of index levels, let’s get into more detail about the key differences between them.

The Thickness of the Lenses

Like we mentioned earlier, different index levels are representative of different lens thickness levels. This thickness operates on a low to high scale, with low-index referring to thicker lenses and high-index referring to thinner lenses. In the past, having a higher prescription often meant having thicker lenses in your favorite prescription glasses. Nowadays, you can get the best of both worlds with a thinner, slimmer high-index lens that can correct the blurriest of vision.

The Materials Used to Make High Index Lenses

While all lenses are produced using plastics or glass, high-index lenses are crafted using high-quality options that are specially produced to bend the light most effectively. They are often just as durable, or even more durable, than their thicker, lower-index counterparts.

The Prescriptions That They Can Accommodate

When looking at the prescription strengths different lenses can accommodate, high-index lenses reign king. These lenses work well for those with prescription strengths from +/-4.00 and higher, with the biggest difference seen in prescriptions of +/-8.00 and higher. Many standard plastic or glass lenses only work well up to about +/-4.00 before the thickness factor begins to take center stage.

The Pros and Cons of High-Index Lenses

We’ve discussed index levels and the differences between each - now it’s time to put it all together and talk about the pros and cons of high-index lenses.

Pro: They’re Thin, Lightweight and Can Fit Your Favorite Frames

For those of us with high prescription strengths, we know the struggle of trying to find lenses that don’t look like bottle caps and weigh 100 pounds. Sometimes we’re even limited with the frames we can purchase based on how thick our lenses are! With high-index lenses, you can get the designer frames you want without worrying about their appearance or the lenses being too thick to fit. Because high-index lenses are so much thinner and lighter in weight than their low-index counterparts, they can be easily customized to fit any frame.

Con: They’re Not as Durable as Other Lenses

Although they’re designed from sturdy plastic or glass, high-index lenses are a bit more fragile than their lower-index counterparts. This is mostly due to their slim design, which is thinner and more easily broken than a thicker lens. It’s important to take extra care both when wearing and storing your favorite prescription eyeglasses if you opt for high-index.

Pro: They Can Be Customized to Suit Your Unique Needs

Not only do high-index lenses offer the ability to cater to a wide selection of prescription strengths, but also, they offer the opportunity for further customizations to suit your unique needs. Whether you suffer from astigmatism or are looking for a pair of prescription glasses with transition lenses, you can get exactly what you need with high-index lenses.

Con: They Can Be More Expensive Than Other Lenses

While high-index lenses offer a lot of benefits, they can come with a cost. When purchasing prescription eyeglasses, standard lenses are often included at no cost, whereas high-index lenses are offered at a premium price-point. It’s important to consider your options and what you need to fit with your lifestyle before you make a purchase.

Pro: You Can Get Them in Sunglasses Form

Love the idea of high-index lenses but a little stuck on what to do with your prescription sunglasses? Never fear - you don’t have to choose between one or the other. Many sunglasses, including our collection of stylish prescription sunglasses, can be purchased with high-index lenses included, allowing you to get the benefit of a high-index lens in the perfect eye-protective tinted lens form.


When it comes to choosing the perfect pair of prescription eyeglasses, always make sure to take the time to consider your lenses. If you have a higher prescription or are looking for something a little more modern, high-index lenses might be the right choice for you. These thin, lightweight and customizable lenses are able to handle a wide range of prescription strengths and can be easily fit into any of your favorite designer eyeglasses frames.

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