Anybody who wears eyeglasses knows how much you pay for two tiny pieces of glass. Take our advice on shopping for glasses online to save yourself a whole lot of cash.

I discovered that a light lens prescription would make my long hours logged at the computer all the more comfortable. I'd never had glasses before in my life and wasn't conditioned to the astounding cost of prescription eyewear. When the bill totaled more than $700 for my modest eyeglasses frame and lenses. I justified it at the time via the added comfort and headache-free computer time; I told myself that, for that price, surely the lenses had been polished with the tears of angels and would last forever.

One year later, I scratched the Hell out of one of the lenses by hastily cleaning it on my shirt, and I shivered at the thought of ordering another $400+ pair of glasses just to get back to scratch-free vision. I remembered reading various accounts online about people buying glasses sight unseen, using their prescriptions from recent eye exams. We discussed just such a trick here several years ago, and more recently here. Our coverage of blogger Matt Haughey scoring a pair of perfectly fine glasses for $60 when he had previously been paying $500 or more for custom glasses stuck in my mind. So much so that I was more than willing to gamble with the technique—even if I had to order multiple pairs of glasses to get it right, I'd still come out ahead by a C-note or two.

Ordering is even easier if you know your papillary distance—the measurement between your two pupils. While the PD of most adults falls in a pretty close range and using an average will work in a pinch, knowing the exact distance for your face ensures the center of the eyeglasses lens is placed directly over your pupil. The more powerful your glasses prescription, the more important the lens is to be properly centered. You can ask to be measured for your PD when you get your eyes examined, or have a friend photograph you with a ruler for scale and check the distance that way. Be prepared to get a lecture about the dangers of buying eyeglasses online if you ask for your PD at the optometrist.

Keep your eye out for deals on websites. Not only are the reviews informative, but there are entire forums devoted to discussing eyeglasses and related information. A stop there can easily score you a coupon for 75% off, with some great tips to boot.

If you already have a pair of glasses you like, carefully measure the size of the lens for reference. It may not seem like much difference, but if your current lenses are 65mm wide and you like the way they look, 55mm wide ones might feel awkward.

So what are the downsides to ordering online? You don't get the tweaking you get when ordering from a local shop. If you need the frames adjusted or the nose pads swapped out, you're largely out of luck, unless you want to ship them around or pay to have a local shop work on them. Also, short of taking them to a local place, you're taking it in good faith—with your eyes to verify—that the prescription is accurate and filled correctly. With savings in the range of 500%-700%, though, it's pretty easy to write off these issues.

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