What happened Shares of Glaukos Corp (NYSE: GKOS), a medical technology company focused on glaucoma treatment, were down about 9.8% as of 11:46 a.m. on Thursday in response to a second-quarter earnings report issued after the bell on Wednesday. Although sales of the company's pressure-relieving stents are surging, the market isn't pleased with the bottom line dipping into negative territory. So what Second-quarter sales of Glaukos Corp's iStent and related products surged 45% higher than the same period last year, but the bottom line didn't follow the top. The company's operations lost $3.9 million during the second quarter, which is hardly what you'd expect given the $2.1 million operating profit recorded during the second quarter last year and the huge sales increase. Image source: Getty Images. Management blamed the loss on a $5.3 million in-process research and development charge associated with the recent acquisition of an intraocular pressure sensor system from DOSE Medical. I'd say the huge 63% on-year increase in sales, general, and administrative expenses during the second quarter is a bigger concern. Now what This was the 16th straight quarter that Glakous Corp's sales rose more than 40% from year to year. While that should be extremely encouraging, rapidly rising SG&A expenses suggest eye surgeons need a great deal of prodding to begin using the company's stents. During the post-earnings conference call, Glaukos stated it had trained about half of 5,500 surgeons targeted and expects to reach 700 this year. That's a huge lead over the company's only real competitor in the space at the moment, but Novartis has a great deal more resources to promote the stent it launched in the U.S. last year and more recently in the EU. At about 10.5 times trailing-12-month sales, Glaukos shares aren't cheap. If the market gets a whiff of success for Novartis' CyPass Micro-Stent in the quarters ahead, Glaukos stock could fall much further than it has today.10 stocks we like better than GlaukosWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the 10 best stocks for investors to buy right now... and Glaukos wasn't one of them! That's right -- they think these 10 stocks are even better buys. Click here to learn about these picks! *Stock Advisor returns as of August 1, 2017Cory Renauer has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.