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According to the National Eye Institute, more than 150 million Americans have some form of common refractive error, meaning their eyes are unable to focus properly.

Generally, medical professionals consider eyeglasses to be the safest way to correct your eyesight. Unfortunately, if you have a strong prescription, regular eyeglass lenses can be thick and heavy.

Thankfully, many retailers offer special high index lenses that you can choose in place of regular lenses. High index lenses are thinner and lighter, making high strength prescription eyeglasses and sunglasses more comfortable to wear.

Read on to learn more about these specialty lenses and to see a list of trustworthy places to buy them.

Regular eyeglass lenses correct your vision by bending light. High index lenses are thinner because they’re designed to bend light more efficiently.

How high index lenses work

The term high index refers to the refractive index, a number that indicates how efficiently a lens can bend light. The higher the index, the thinner the lens.

With high index lenses, even those with strong prescriptions can sport many types of frames. This includes rimless or half-rim frames, which typically don’t suit thicker lenses.

Essentially, the higher your prescription, the higher the index you’ll want. For comparison, regular plastic lenses have a refractive index of 1.50.

The most common high index lenses are:

  • 1.61: about 25 percent thinner than regular lenses and best for prescriptions of +3.00/-6.00 or less
  • 1.67: about 30 percent thinner and best for prescriptions under +5.00/-8.00
  • 1.74: at least 35 percent thinner and best for prescriptions over +5.00/-8.00

Note that a plus sign (+) in your prescription is an indication of a farsighted correction, and a minus sign (-) is an indication of a nearsighted correction.

Should you get high index lenses?

High index lenses can correct a wide range of refractive errors, including nearsightedness (myopia), farsightedness (hyperopia), and astigmatism.

You can get them as single vision lenses, reading glasses, bifocal, or progressive lenses.

They’re designed for eyeglass prescriptions of greater than +/- 2.00 and are generally recommended for prescriptions approaching or exceeding +/- 4.00.

If you’re unsure if you should opt for these specialized lenses, talk with your optometrist or eye doctor. They will be able to tell you if you’re a good candidate.

Not only will they look at your prescription strength, but they can also help you find styles that you like that suit your lenses. Even if you have a strong prescription, you can sport many different frame types with high index lenses. This includes rimless or half-rim frames, which typically don’t suit thicker lenses.

Cons of high index lenses to consider

The most significant con of high index lenses is their higher price point.

Further, because these lenses reflect more light, you’ll likely need to add an anti-reflective coating. This may come with added cost, as it’s typically an add-on feature.

Finding a retailer of good quality high index lenses can take a little digging. We’ve cleared the way for you with this list of reputable retailers that sell high index lenses online and in-store.

Warby Parker

Warby Parker is known for offering in-house designer specs at good price points.

They boast a strong online business, as well as brick-and-mortar stores in 71 locations in 28 states in the United States.

By visiting them in-store, you can try on glasses, talk to staff about their high index options, and have your measurements taken. You can also use their free home try-on service, which allows you to pick five frames to try at home for free.

  • High index lens options: 1.67 and 1.74
  • Price: their 1.67 lenses cost an additional $30, while their 1.74 lenses cost an additional $130
  • Shipping: free

BonLook

Canada-based BonLook produces their own line of frame styles. If you shop online, you can use their virtual try-on tool and sizing guide to help with frame selection.

In addition to their online experience, you can shop at BonLook retail shops throughout Canada.

  • High index lens options: 1.67
  • Price: their 1.67 lenses cost an additional $30
  • Shipping: free for orders over $80; otherwise, it’s $10

Zenni Optical

Zenni Optical is an online-only retailer of prescription glasses known for bargain-basement prices. They’re able to keep their costs low by selling directly online to consumers.

  • High index lens options: 1.61, 1.67, and 1.74
  • Price: their 1.61 lenses cost an additional $19.95, their 1.67 lenses are $34.95 more, and their 1.74 lenses are $74.95 more
  • Shipping: $4.95

GlassesUSA

This online eyeglass retailer is known for its huge selection of frames at affordable prices.

GlassesUSA has a virtual try-on tool and lots of options for add-on coatings and lens treatments. While these coatings and treatments increase the price, they can improve the look and feel of your eyeglasses.

  • High index lens options: 1.67
  • Price: their 1.67 lenses cost an additional $98, which includes scratch and anti-reflective coating
  • Shipping: free

EyeBuyDirect

Similar to Zenni Optical, this direct-to-consumer eyeglass retailer offers an easy-to-use online shop.

EyeBuyDirect has a large selection of frames, including brand names like Oakley and Ray-Ban, as well as solid options for lens treatments that prevent scratches, glare, and smudging.

  • High index lens options: 1.6 and 1.74
  • Price: their 1.6 lenses costs an additional $30.90 and their 1.74 lenses cost $89.90. Both include ultraviolet (UV)-protective, anti-scratch, and anti-reflective coatings. The 1.74 premium lens features anti-scratch, anti-reflective, UV blocking, anti-smudge, and dust and water-repellent coatings for an additional $124.90
  • Shipping: free on orders over $99; otherwise, it’s $5.95

LensDirect

LensDirect has no in-store presence but offers a simple, straightforward online shopping experience.

What’s more, all their orders include lenses with 100 percent UV protection, as well as anti-reflective and scratch-resistant coatings.

  • High index lens options: 1.67 and 1.74
  • Price: their 1.67 lenses cost an additional $34 and their 1.74 lenses are $79 more
  • Shipping: free

Your local optometrist

Your local optometrist’s office is also a great place to go to learn about high index lenses. If you have specific lens requirements or concerns, you may feel more comfortable with in-person shopping.

If so, you’re not alone. In fact, a 2016 study found that many customers in the United Kingdom preferred glasses purchased at their optometrist’s office. This was because buying online typically led to “poor frame fit, poor cosmetic appearance, and inaccurate optical centration.”

Shopping at your local optometrist’s office also allows you to try on frames before committing to see if they’re comfortable and suit your style. After your purchase, you’ll also be able to stop by the shop to address any issues with your new specs quickly and easily.

In addition, your optometrist can accurately measure your pupillary distance (PD), which ensures that your pupils are at the center of your lenses. If you shop for eyeglasses online, you may have to determine your PD on your own, and it may not be as accurate.

The PD measurement is especially important if you have a strong prescription. If an incorrect number is used, your vision may be distorted or blocked by the frame.

By more efficiently bending light, high index lenses can cater to strong eyeglass prescriptions while remaining thin and light.

This allows you to choose from a larger selection of eyeglass frames, but it’ll also add to the cost of your new lenses.

Many online and in-person retailers offer high index lenses, with some of them including special features like UV protection or scratch resistance. Be sure to do your research and find a retailer that suits your preferences and budget.