Complex sentence: They are one of the largest online contact lens retailers in North America, and the largest seller of prescription eyeglasses online in the world; in 2011, the company sold more than $180 million of merchandise.
Split into simpler sentences: They are one of the largest online contact lens retailers in North America, and the largest seller of prescription eyeglasses online in the world. In 2011, the company sold more than $180 million of merchandise.