For eyeglasses and contacts, we usually found the least expensive sellers online. But for contacts, you can’t count on low prices from all internet sellers: Some offered higher prices than many brick-and-mortars.

We shopped prices at a sampling of online retailers using the same list of eyeglasses (including lenses for a simple prescription) we used to compare prices among local stores. For eyeglasses, prices at almost all of the online retailers we shopped were substantially lower than surveyed local stores—several online stores offered prices that were less than half those offered by local outlets. Some online sellers not only offered very low prices, but also carried a much wider selection of frames than any of the local outlets.

We also compared prices for contact lenses from online retailers with those at local stores (see table below). For local contact lens dispensers, we included their fees for eye exams and fitting. To compare prices at online contact lens sellers with local stores, we added the average cost of an eye exam and fitting at local vision centers to each of the online seller’s prices.

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After factoring in the cost of exams and fitting, we found that several online contact lens sellers offered prices that were at least 30 percent lower than the average prices at local stores, but as you can see on the table below, some well-known online sellers offered prices that were higher than the average prices offered by the lowest priced local outlets.

There are some disadvantages to shopping for contacts and eyeglasses online. It’s possible that the prescription may be incorrectly filled or that the seller may send the wrong contact lenses. But these problems could also occur with a local seller.

If you are a new contacts wearer, or trying out a new type of lens, at first buy a minimum number of lenses from a local outlet; then, if they work out, buy from online retailers in the future. Even better, ask your doctor for a sample pair of lenses to try out before you have your prescription filled. By taking this approach, you identify any problems right away, before you’ve paid for a year’s supply of lenses.

An obvious disadvantage of buying eyeglasses online is that, unless you’re replacing frames you like with an identical model, you can’t try on various frames to see how they’ll look on your face. One strategy is to visit local stores, try on frames to find ones you like, and then buy online. Also, many sites let you upload a picture of yourself so you can try on frames virtually; others send out sample frames for free, letting you try them on at home for a week before ordering your own. Fortunately, liberal return policies are the norm among online sellers, so you can return glasses easily if you’re not satisfied.

Another problem with ordering frames online is that you’ll have to find a local solution for obtaining any adjustments. Fortunately, most optical shops make small adjustments for free, even for consumers who bought elsewhere.