You can save hundreds, but these cut-rate specs come with some caveats. December 11, 2008 by Ryan Wilk More than a year has passed since your last eye exam, so you drop by your local boutique for a quick checkup. An hour later -- and $500 poorer -- you're out the door, wondering how a simple prescription framed in a piece of plastic stamped "Made in China" could cost so much. But thanks to some online retailers, getting a new pair of specs doesn't have to break the bank. The savings can be dramatic. These factory-direct glasses run from about $8 to $50 for both frames and lenses -- but they come with two caveats. First, you'll need to do a little work to put in an order. Second, the quality ranges from pretty good to flimsy, more or less in proportion to the price you pay. Charles Bailey, an associate clinical professor at the University of California-Berkeley optometry school, says the frames may have shoddy hinges, or the protective lens coatings may be of lesser quality than in pricier eyeglasses. However, they're worth considering, especially to use as a backup pair or to expand your eyeglass wardrobe on the cheap. The Web sites themselves also vary in quality. The best -- 39DollarGlasses.com and EyeBuyDirect.com -- offer a big selection and an easy-to-use, uncluttered interface. But others, such as Optical4Less.com, can be tricky to navigate. And some, such as ZenniOptical.com, are usable but downright eyesores. For advice on getting the best fit for the best price, we checked with Ira Mitchell, who runs a Web site on the online eyewear industry, GlassyEyes.com. Mitchell, a software developer in St. Paul, says he owns 18 pairs of glasses from various online retailers. "Of the 18 pairs that I've gotten, 17 have been great." Advertisement Proper fit Make sure you have an accurate, updated prescription, Mitchell says. By law, your ophthalmologist or optometrist is required to give it to you. You'll also need to know your pupillary distance (PD), which is the distance between the centers of your pupils, to ensure a proper fit. Your optometrist should be able to give you that number, but most online retailers also provide instructions for measuring it yourself. Because calculating your own PD can be tricky and imprecise, ask a friend for help to save you the trouble of fumbling with a ruler in front of the mirror. Next, look at an old pair of frames and jot down the measurements -- they're usually on the inside of the frames. If you can't find the size, try on a few pairs with clearly marked sizes at an optometrist's office. Armed with that information, shopping for glasses online is as straightforward as buying anything else. Most retailers let you filter their inventories by style and frame size, so you don't have to sort through countless frames. Some even let you upload a picture of your face so you can virtually see yourself in different styles. Advertisement After "trying on" dozens of pairs, I settled on $19 plastic frames from Zenni Optical. I opted for high-index lenses with anti-glare coating -- a $20 upgrade, but the total was still hundreds less than I would pay in stores. Similar designer glasses by Oliver Peoples cost about $530. My pair was not as sturdy as the Peoples pair, but they looked just as sharp, and I could see just fine. The glasses, along with a case and cleaning cloth, arrived in two weeks. If you have bifocals or a strong prescription, says Bailey, be certain your measurements are accurate (especially the PD). If there's an error, your glasses may cause eye fatigue or double vision. If the prescription is wrong or your frames don't fit properly, most online retailers have flexible return policies. Zenni Optical, for example, offers a 50% refund within four weeks, and EyeBuyDirect.com gives a full, no-questions-asked refund within seven days.