Although it offers full-frame/lens packages, Lensabl puts its lens replacement service front and center and ranks highly in search results for "lens replacement." Its motto is "Your frames, our lenses," with prices starting at $97 for a basic pair of single-vision lenses. The budget new lens options are decent enough, but it does make a difference (in terms of sharpness and clarity) to step up to lenses more in the $150-plus range. 

You upload your prescription online and pick the type of lens you want, and then Lensabl sends you a box with a prepaid return shipping label. You simply mail in your old frame in the box (shipping is free). First-time prescription lens customers get 15% off. 

Lensabl does make prescription lenses for Bose Frames and other audio sunglasses.

Notable site features: For $25, you can renew your prescription online through the vision prescription platform Visibly. Not everybody qualifies to take the online eye exam -- you have to answer some questions to see if you qualify -- but if you do, Lensabl says, "All you need is your computer, [your] smartphone and about 15 minutes of time." Your results will be reviewed by an eye doctor or optometrist licensed in your state who will then issue you a new prescription via email.

Current deals and coupons: All of Lensabl's deals and promo codes are displayed on its homepage.

As its name implies, Overnight Glasses can make you a new set of prescription glasses quickly -- and really quickly if you're willing to pay extra for a new pair of glasses. For lens replacements, you get free USPS round-trip shipping. For orders over $150, you get free two-day air shipping. (It takes slightly longer for progressive lens and bifocal lens types.) The quality of the lenses I got was as good as that from other replacement lens sites, so there's no sacrifice of prescription eyewear quality for speed.

As for new lenses for your current frame, you ship your frames to Overnight Glasses, and it'll replace your lenses with new ones in as few as five days. The service can do polarized, blue light, transitions and many other types, although progressives require additional time.

If you're looking for a truly overnight option, there is a 24-hour rush service. Bifocal, no-line bifocal and progressive lenses can take an extra day to manufacture.

Overnight makes lenses for Bose Frames and Amazon Echo Frames audio glasses.

Notable site features: The site has a clean, easy-to-navigate design. There are multiple shipping options.

Eyeglasses.com has a huge selection of both frames and lenses and is also one of a small number of sites that offer a lens replacement service for existing frames, with prices starting at $48. As with all the other sites here, you simply choose the lens you want (that can be a little daunting because there are so many options) and you'll get sent a prelabeled box with which to return your frames, with free shipping both ways. If you don't know your prescription -- and don't want to change your current prescription -- you can opt to have Eyeglasses.com's technicians "read your lenses and duplicate them." 

The service isn't superspeedy in terms of turnaround time, but the lenses are high quality, and the eyewear site has good online help options, including a Replacement Lenses information page and an online chat feature. Unlike Lensabl, which highlights its lens replacement service, Eyeglasses.com doesn't market the options front and center. 

Eyeglasses.com makes lenses for Bose Frames and Amazon Echo Frames audio glasses.

Notable site features: Eyeglasses.com says it sells only "high-quality, individually made lenses made in the USA," and the sample glasses I tried had excellent lenses that gave me a very sharp image. There's a huge selection of lens options, and you get a "Perfect Lenses Guarantee" that allows you to send your glasses back if they don't work for you -- you can get a redo or a full refund, your choice.

Current deals and coupons: Eyeglasses.com has a coupon page with current deals.

It's had shops in the New York area for a while, but ReplaceRxLenses is somewhat new to the online replacement-lens arena. My experience using this retailer was smooth, with a relatively quick turnaround time (about a week, but I was in New York). Its prices are competitive and slightly cheaper for some lens types, starting at $55.

The site says what differentiates it from competitors is that it doesn't have an assembly-line format for fulfilling orders, where one worker is responsible for manufacturing the lenses, another is responsible for tracing the frame and edging the lenses to fit the frame, and another might handle the final eyeglass inspection. "With us, one technician works on a customer's order from start to finish," a rep told me. "We believe this format results in a better end product, because there is almost no chance of information being lost or mistakes being made along the way."

ReplaceRxLenses says it can do a replacement for prescription eyewear or replace nonprescription lenses for Bose, Amazon Echo, Snapchat Spectacles and many other audio/smart frames.

Notable site features: The site says it has experience working with frame types and lenses that some other places can't handle. "We have plenty of experience working with sports frames, wraparound frames, vintage frames and extended range prescriptions," a rep told me. "Many other online replacement services can only work with certain frame types and up to certain prescriptions."

The site tries to get as much information about a customer's frame beforehand so it can begin working on the order even before receiving the frame, which helps expedite the order. (I submitted a photo of my frame.)

Current deals and coupons: 10% off for new customers in exchange for your email address.

LensDirect says it can make quality lenses for a wide array of frames -- "practically any frame unless it just absolutely doesn't make any fundamental sense like putting a +7.5 prescription on a semi rimless frame" -- and has its own machine in-house that can cut the lenses anytime (other retailers have this as well). "We make lens replacement more affordable than our competitors without sacrificing quality," a rep told me.

LensDirect now makes replacement lenses for Bose and Amazon audio glasses, although it does require you to sign a waiver to work on them.

My lens replacement took about a week, and the lens was of high quality. After using discount codes, the cost for the lenses I got was a bit less than that from some competing sites like Lensabl.

Notable site features: The site has a virtual try-on feature if you're buying a frame and lens package.

For an older audience (people who wear progressive or bifocal lenses), lens options tend to be more affordable (with discount codes applied), especially for the 1.67 high-index lens, which is 40% thinner and lighter than a standard CR39 lens.

"Even to a younger audience who wants to take a cheap eyeglass frame and get exactly the lens they need, our CR39 and Polycarbonate lenses start off more affordable even for them," a rep said.

If you currently have a frame with prescription lenses, you should be able to replace those lenses with a fresh pair. Certain types of glasses that have more curved lenses -- such as those found in some sports glasses -- may be harder to replace. Just make sure you check with the company you’re using before sending in your frame.

You can put old lenses into a new frame as long as the new frame is the same as the old one and the lenses are still in good condition. Some eye care providers may be able to shape old lenses into the new frame, but it's not always possible.

Depending on the quality and type of lens you get, it can be expensive to put new lenses in old frames. If you are just getting basic lenses, it can be quite affordable, especially when buying from an online retailer.

For pure clarity, a glass or mineral glass lens is the best. Most people prefer polycarbonate lenses, which are lighter and more durable. High-index lenses are good for those who have strong prescriptions that would normally require thicker lenses. These high-tech plastic lenses end up being the same thinness as standard plastic or polycarbonate lenses that have a lighter prescription. You do have to pay more for high-index lenses. Arguably the best lenses are Trivex lenses, which are lightweight and durable and offer slightly better clarity than polycarbonate lenses. They are more expensive than plastic (CR-39) and polycarbonate lenses.

Most eyewear retailers make prescription lenses for audio glasses, like the Amazon Echo Frames and . Only a few have officially partnered with Bose, like Lensabl and the Bose Tempo sports model. Aside from the Tempo, most other audio glasses have pretty standard frames that accept prescription glasses. You can always call and ask whether the company can make lenses for whatever audio glasses you have based on your particular prescription.  

Delivery times vary by retailer, but you will typically get your replacement lenses in 5-14 business days. This includes the time it takes to mail your frames to the company, have new lenses made and installed and ship them back to you. Some services have expedited shipping options available too.