shopping for glassesI have worn glasses since I was 17. I started needing them on a regular basis in college and have faithfully gone every year to my eye doctor for an exam and a new pair. Frames are so expensive, even with great vision insurance, but now there are affordable and stylish alternatives like Firmoo and Warby Parker. Here’s a breakdown of how they work, and three tips for getting the most out of purchasing glasses online instead of at an optician’s or franchise glasses store.

1. Have a recent (within the year) prescription: This is obviously the most important part of ordering glasses online, because you need to know your exact prescription to scan or input. You will also need to know your PD (pupillary distance measurement).

2. Look at your current glasses: It’s important to have an existing pair of glasses so you can look up those numbers on the arm. Here’s how Warby Parker describes what to look for:

The frame measurements are listed as three numbers. The first number refers to the width of one lens in millimeters, the second number to the width of the bridge, and the third to the length of one of the temple arms.

Once you know that about your current frames, you can compare to the frames on an online glasses retailer.

3. Upload a closeup photo or headshot: On certain sites, you can upload a photo of yourself (without glasses!), so that you can virtually try on frames. Of course, this won’t be 100% accurate, but you should get a feel for what the glasses look like on your face.

Firmoo’s Pros & Cons: It’s super easy to order from Firmoo, an international glasses site that calls itself the “world’s most popular online eyeglass store.” There are so many options, and most of them are less than $30. I uploaded a photo of myself and “tried on” a bunch of glasses that were recommended for my PD. Once I picked my frames, I had several options I could add on, like special coatings, thinner lenses, and more. The shipping was free to the U.S., and the only downside is that you can’t physically try on the frames before committing to a pair. If you know precisely what shape and style you want, this is an easy-to-use and affordable choice. You could easily buy a pair of prescription glasses for less than $60. Firmoo also offers sunglasses and has a responsive customer service.

Warby Parker’s Pros & Cons: You’ve probably seen their ubiquitous ads, but Warby Parker is another great choice to buy glasses online. Of course, they also have brick and mortar stores, so if you live in NYC, Boston, Philly or DC, you can just pop in and order right there. But everyone can choose up to five frames, which are shipped so people can “try before they buy.” Before you pick the five frames for your home try-on, you can consult a stylist to help you select the right five frames for your taste. Once you’ve tried on your frames, you pick the one you like best and $95 (or more if you require a higher-index lens) later, you have a new pair of glasses. Warby Parker also offers sunglasses. The only downside is that there’s a flat fee for glasses, so they’re not going to be any less than $95 like they are Firmoo. But the home try on and the customer service are unparalleled in the market.

Diclosure: Firmoo provided complimentary frames for this review. I purchased the Warby Parker pair myself.