Mark Shand, a Google Glass engineer with a long history in tech, shows off a prototype Google Glass fitted for prescription glasses. FoxNews.com / Perry Chiaramonte A special, prototype version of Google Glass for eyeglass wearers was spied on the faces of at least three engineers and developers at the Google I/O conference, CNET"s Seth Rosenblatt reported. Rosenblatt said he saw Mark Shand, a Google Glass engineer with a long history in tech that stretches back to Xerox PARC, wearing a prototype model fitted for prescription glasses. Glass for the eyesight-impaired replaces the titanium band in the standard model with a generic pair of black plastic glasses, onto which the display arm and other components are melded. Many experts have surmised that manufacturers such as Warby Parker, which has refocused the eyeglass industry through online sales of inexpensive eyeglasses and sunglasses, could offer Google Glass as an option for consumers. Alternately, the manufacturers of protective eyewear for sports -- such as Oakley, which has a history with high-tech gear -- may offer integrated modules.