(MONEY Magazine) – About 24 million Americans wear contact lenses. So what? So this: At least half of them probably paid double or more what they could have for their first pair of lenses and subsequent replacements. That's because 50% of contact wearers order their plastic through private optometrists or ophthalmologists at prices that are routinely twice what discounters charge. A case of eye gouging? Not really. Private practitioners, who normally depend on product sales for a fifth or more of their revenues, can command such high prices because they know lens buyers prefer individualized care and one-stop shopping. These days, however, savvy consumers can find top-quality lenses at prices calculated to make your local optometrist weep. Since the mid '80s, competition for lens buyers has become increasingly keen. Nationwide optical chains such as Pearle Vision have been joined by newcomers such as Wal-Mart, Sam's Wholesale Club, K Mart, Caldor and mail- order outlets like Lens Express. Even supermarkets and discount drugstores are in the act. The upshot: lens prices that average 50% lower than those at your local eye doc. For example, popular brands such as Ciba's Softclear daily-wear lenses cost only $17.50 a lens at Family Vision Centers in 125 Sam's Wholesale Clubs and seven Wal-Marts, while the average optometrist charges about $50 a lens. ^ What's more, if you're comfortable with the idea of getting your eyes checked in a nontraditional setting, many of the new outlets, including Wal- Mart, now offer eye exams, lens fittings and follow-up care by licensed optometrists for as little as $50, compared with $60 to $75 at most private optometrists. Fittings and follow-up alone run even less -- about $35. Naturally, cost is hardly your sole consideration. Cautions Michael G. Harris, chief of the Contact Lens Clinic at the University of California's School of Optometry at Berkeley: "Contact lenses are medical devices and can cause serious complications if used improperly. "So MONEY canvassed dozens of eye-care practitioners, manufacturers and distributors to turn up the best deals without putting your eyes at risk. The advice: -- You need a prescription before shopping. All lens retailers require a prescription no older than one to two years, depending on your home state. If you'd rather be examined by a private doctor and then shop for lens bargains, ask the practitioner for your prescription. Sixteen states -- Alabama, Arizona, Colorado, Delaware, Florida, Maine, Nevada, New Jersey, New York, North Carolina, Ohio, Oregon, South Dakota, Texas, Vermont and Virginia -- require your optometrist to release prescriptions, usually after you've been fitted with a first pair of lenses. Elsewhere, doctors may refuse to hand over the prescription, either because they worry you won't return for follow- up care or because they're trying to boost profits. But always ask. Many doctors will comply. -- Understand your lens options. Preferred by 86% of all wearers, soft lenses divide roughly into three types: Conventional daily-wear lenses, introduced in 1971 by Bausch & Lomb, are still the most popular, selected by 47% of wearers. They usually cost $50 to $100 a pair (depending on discounts and prescription), require nightly cleaning and weekly enzyme washes and are designed to last about a year. The advantage of daily wear over other soft varieties is low cost: about $250 a year, including cleaning solutions. The drawback is that protein deposits tend to build up over time on daily-wear lenses, and that can cause eye irritations. As a result, frequent-replacement lenses, introduced in 1984, are attracting more customers -- 11% of all lens wearers in 1993, up from just 1% in 1990. These lenses cost more on a yearly basis than daily-wear lenses do -- about $350, including cleaning solutions. But because you replace them every two weeks to three months, they remain freer of potentially irritating grime. Disposables, introduced in 1988, are the fastest-growing option -- 28% of wearers, up from 18% in 1990. These cost $7 to $9 a pair (with cleaners, about $400 to $500 annually) and are worn for one to two weeks, then discarded. Disposables, unlike the daily-wear types, omit the enzyme wash because there's no time for dirt to build up. Extended-wear lenses were developed in 1981 for people who want to sleep in their lenses. All three types -- daily wear, frequent replacement and disposables -- can be found in extended-wear versions. Usually, you don't pay extra for the extended-wear option, but beware. Sleeping in these lenses has been consistently linked to inflammation of the cornea. If low price counts most, consider rigid gas-permeable (RGP) lenses, the latest incarnation of the original hard lenses introduced in 1939. Today's RGPs are easier to wear than the earliest versions because they allow more oxygen to reach the eye. Removed and cleaned each night, hard lenses initially cost about 20% more than daily-wear soft lenses but will last two to six years -- sometimes longer. Hard lenses also provide the best vision correction of all lens types, especially for tricky bifocal prescriptions. Cleaning supplies run about $100 a year. -- Don't be a patient, be a consumer. Be skeptical about lens manufacturer labels that specify how frequently you should replace the lens, known as wearing schedules. Bausch & Lomb, for example, came under fire last July after an investigation by Business Week revealed the company was selling the same lens for various kinds of wear at widely ranging prices. Yet the only difference among the company's Optima FW ($40 a lens), Medalist ($9) and SeeQuence 2 ($4) was the packaging. B&L's official response: "The lenses are sold to eye doctors at three different prices based on a graduated system of volume discounts. It is the eye-care professional who sets the final price the customer will pay. "Our advice: Quiz your examiner about how strictly you must follow recommended wearing schedules, and ask whether a cheaper lens will do for you. -- Compare prices on lenses. No one outlet has a monopoly on bargains, although mail-order firms seem to have the edge. To give you an idea of where deals can be found, we surveyed 12 retailers and mail-order firms for four popular brands. Here's what we learned: Daily wear. The Family Vision Centers charged just $17.50 each for Ciba's Softclear lenses. Contact Lens Connection (800-695-5367), with no shipping fees, charged $19 each. Disposables. Prices for a six-pack of Johnson & Johnson's popular Acuvue (replaced every one to two weeks) didn't vary much. At most outlets, including the 376 company-owned Pearle Vision stores, you'll pay $19.50 to $25. Frequent replacement. A six-pack of Bausch & Lomb's Medalist (replaced everyone to three months) was cheapest at the mail-order Contact Lens Supply (800-833-7525), which charged $65 for two six-packs plus $4 for shipping -- or $34.50 a pack. Rigid gas-permeable. A pair of Boston RXD RGP lenses were lowest at the Family Vision Centers -- $64. Dial A Contact Lens (800-233-5367) charged $77, plus $5 shipping. One final shopping tip: Many mail-order suppliers, such as the largest firm, Lens Express (800-666-5367), will match the lowest retail prices you can find. Just make sure you factor in the shipping costs before you take the deal.