NEW YORK – Want to spend less for good-quality prescription eyewear? A growing number of websites cater to people willing to make this most individual of purchases online.

New sites like Warby Parker (www.warby parker.com) and the upcoming eyefly.com from clothing and accessories seller www.bluefly.com — plus more established players like www.framesdirect.com and www.39dollarglasses.com — are defying conventional wisdom that people want to touch before buying certain products. And for many shoppers, the move online is seamless.

Starting with technology that determines the shape of your face from a digital photo, the sites say they offer the same service and personal attention as a brick-and-mortar shop, but with better selections of frames and at lower overall prices.

So far, however, less than 3 percent of the estimated $25 billion that Americans spend annually on eyewear, including contact lenses and non-prescription sunglasses, goes to online purchases, according to The Vision Council, a trade group representing manufacturers and suppliers. For prescription glasses, which totaled $17.7 billion in sales last year, online sales accounted for about 1 percent.

Warby Parker, which has sold more than 50,000 pairs of glasses since its February 2010 launch, says its $95 prescription glasses are comparable to eyewear that would sell for $500 at a high-end boutique. The difference is that Warby Parker’s frames don’t carry designer names and it cuts the number of middlemen between manufacturers and consumers, says co-founder Neil Blumenthal. Blumenthal estimates that manufacturers typically charge upscale retailers about $100 for the same designer frame that costs consumers $300 at retail. Likewise, he says, lenses that consumers pay $200 for at retail typically cost opticians about $65.

Buying prescription eyewear online also can let you check out hundreds of different frames — by manipulating the photo you upload — and it can mean spending a lot less time on the process.

But there are plenty of pitfalls.

Amy Klaris, a retail strategist at Kurt Salmon, says “there’s still a lot of worry” about buying eyewear online. She also says shoppers want to be able to return glasses they don’t like or find uncomfortable.

In fact, Sam Pierce, a board member of the American Optometric Association, which represents 36,000 doctors of optometry, says preliminary research has revealed some eyewear prescriptions are not being filled accurately online. Pierce’s group and the Vision Council plan to release a joint report this summer examining the safety of buying prescription glasses on the Web.

Some things to keep in mind as you navigate:

SELECTION: Framesdirect.com, which bills itself as the largest full-service online eyewear company, offers more than 100,000 frames, including some from top designers, and it sells contact lenses. Also offering a generous selection is 39dollarglasses.com. Warby Parker cuts the clutter and produces a complete pair of glasses for $95, but its selection may be too small: about 35 styles, all in acetate and most fairly chunky.

PRICE: If you need a strong correction or like extra-thin or tinted lenses, fees for those extras can add up. High-index lenses can add $30, for instance, and a strong correction another $30.

Be sure to examine each company’s shipping fees too. And remember that any fine-tuning or tightening you need after you’ve worn your glasses a while will have to be done in person, and your local optician may charge for those services if she didn’t sell you your glasses.

RETURNS: Bestbuyeyeglasses.com, for example, doesn’t allow full returns or exchanges but will give you 50 percent off new lenses if you exchange a pair of glasses within 30 days of purchase. Warby Parker, on the other hand, gives you 30 days to decide if you like a pair of glasses and, if you don’t, promises to refund your full payment.

QUALITY OF LENSES: While glasses assembled in the U.S. should have impact-resistant polycarbonate lenses at a minimum, Pierce warns that some labs outside the U.S. may use substandard materials. So do all your homework before you buy.