Castlight Health looks to raise about $111 million in its IPO, according to an updated SEC filing. The company is offering 11.1 million shares in the IPO and its underwriters have the option to purchase an additional 1.65 million shares. The stock will be listed on the New York Stock Exchange under the symbol "CSLT". While Castlight recorded revenues of $1.9 million, $4.2 million and $13.0 million for the past three calendar years, it has posted respective net losses of $19.9 million, $35.0 million and $62.2 million.

Castlight Health works with health plans and other organizations to help self-insured employers offer their employees more transparent health care price and quality data in the form of online consumer tools and via mobile apps. Over the past two years Castlight has inked deals with more than 95 customers, primarily large self-insured employers, that include 24 Fortune 500 companies. At the end of 2013, Castlight had 106 signed customers, 48 of which had implemented its offering. At the end of 2012, it had 47 signed customers, and just 15 launched ones.

Among the many risks Castlight identified in its IPO filing was its limited number of customers that make up the majority of its revenue. Its deal with Wal-Mart and its affiliated health plans, for example, made up approximately 16 percent of Castlight's total revenue last year.

"In addition, in our years ended December 31, 2012 and 2013, our top 10 customers by revenue accounted for 93 percent and 61 percent of our total revenue, respectively," the company wrote.

Another potential issue for Castlight is its ongoing access to the pricing information that its offering depends on. While it works with many of the large health plans in the US, Castlight notes in its IPO filing that it still has no deal with one of the largest payers: UnitedHealth Group. That's because -- as part of a deal with another, unnamed payer -- Castlight agreed not to work with UnitedHealth. 

"In order to deliver the full functionality offered by our Enterprise Healthcare Cloud, we need access, on behalf of our customers, to sources of pricing and claims data, much of which is managed by a limited number of health plans and other third parties," the company writes. "We have developed various long-term and short-term data-sharing relationships with certain health plans and other third parties, including most of the largest health plans in the United States. However, we do not currently have a data-sharing arrangement with UnitedHealth Group, one of the largest health plans, as well as other smaller health plans, which limits our ability to offer the full functionality of our offering to customers of such health plans."

Castlight goes on to explain that the terms of each of its deals with health plans sometimes restricts its ability to partner with their competitors: "In addition, in one agreement with a large national health plan, we agreed, in exchange for more favorable terms to access health care claims data and other strategic benefits, to an exclusivity provision that restricts our ability to provide our full offering to customers of UnitedHealth Group, Inc. until January 2015."

Among Castlight's future plans and stragies for growth: building out its platform by offering new applications and integrating with third party apps.

"We have only recently begun to offer additional applications to our customers and have experienced positive results," the company writes. "For instance, our pharmacy application, first launched in 2013, integrates prescription drug information into our offering and has been purchased by more than half of our customer base. We are currently developing new complementary applications and services to address additional benefit and engagement needs."

The company is also expecting others to integrate with its platform: "Additionally, we expect third-party developers will leverage our application program interfaces, or APIs, and our database to develop a broad range of value-added applications and services accessed via our platform, thereby further enhancing the value of our offering."