Google is releasing its first collection of four prescription frames for Google Glass. The move comes as the company prepares to make the Google Glass technology available to the general population in the U.S. later this year.

Until now, Google has not had corrective lenses in its frames. Google Glass is still undergoing beta testing and is being offered only to “Glass Explorers,” a group of early adopters reportedly numbering in the tens of thousands.

The new frames can be fitted with corrective glass or tinted glass. The new collection features complete spectacle frames that are fully integrated with Google Glass head-up displays and temple-mounted electronics. Previously, Google Glass wearers who required corrective lenses had to wear them under a thin titanium headband attached to the Glass display.

Internally designed by Google, the new prescription eyeglasses are also relatively stylish and unobtrusive. The four styles in the prescription Google Glass collection are Split, Curve, Thin and Bold. They are all made of titanium and are available in five colors. The four new Google Glass frames and the two shades in the collection will allow Explorers to create up to 40 different style combinations. Available at the Google Glass website, prescription frames for the internet-enabled headset cost $225, in addition to a $1,500 entry fee for the Glass Explorer program. The tinted sunglass shades will cost $150.

The internet search giant has also announced a deal with VSP Global, the American eye-care insurance company that owns Marchon, to make the prescription lenses and to offer them with the frames for Google Glass. This partnership will give Google an opportunity to reach a broader market for the device in the U.S., as VSP has a network of 30,000 eye professionals in the country using its services who can help with the distribution.

Google has also joined with VSP to train eye-care professionals on how to fit the device for customers. The first 200 optometrists trained to fit Google Glass to the new prescription frames are reportedly located in San Francisco, Los Angeles, and New York. Google plans to quickly expand to other cities, training 6,000 doctors by the end of the year throughout the country.

After ordering Google Glass prescription frames through the Google Glass website, Glass Explorers can then take them to an optometrist affiliated with VSP who can measure them for the device, order prescription lenses through VSPOne Sacramento, its flagship laboratory, and then fit the finished eyewear. The list of trained VSP optometrists is available on the Glass website itself as well as on VSP.com.

Separately, VSP has announced that the VSPOne Sacramento lab will move from Rancho Cordova to a nearby location at Folsom in California by next November, occupying 80,000 square meters and employing about to 650 unionized employees at full capacity.

Google's partnership with VSP Global has been going on for more than a decade, as VSP has been providing vision and eyewear benefits to Google employees for about 15 years. The partnership has intensified particularly over the last two-and-a-half years, when Glass was developed.

Business Insider predicted last November that 21 million Google Glass sets would be sold by 2018, resulting in an annual turnover of more than €10 billion for Google.

Meanwhile, competitors are getting ready to launch alternative solutions. Rochester Optical has indicated that it will offer its own range of frames for Google Glass with prescription lenses starting at $99. At the recent Consumer Electronics Show in Las Vegas, another U.S. firm, Vuzix, presented a smart glass priced at $1,000. A couple of French start-ups, Laster Technologies and Optinvent, are reported to have come out with connected glasses.

For its part, Apple has announced that it has filed a patent for its own iGlasses, which will be directly connected by cable to an iPhone, an IPad or an iPod, but they may not become available before 2015. Samsung has indicated that its Galaxy Glass will hit the market in the second half of this year. Other major players such as Sony, Epson, Brother and Olympus, have reportedly all been working on prototypes of similar products.