Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2016

Equity [Abstract]

Summary of Stock Based Compensation Expense

Stock compensation expense (in thousands) was allocated between departments as follows:

	Three months ended March 31,
	2016			2015
Research & Development	$	33		$	50
Sales & Marketing	(31		)	20
General & Administrative	134			331
Total	$	136		$	401

Stock Options Valuation Assumptions

The fair value of each award granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions:

	Three Months Ended March 31,
	2016	2015
Expected life (years)	6.0-6.1	5.5-6.1
Risk-free interest rate	1.5%-1.7%	1.5%-1.6%
Volatility	66% - 67%	57% - 68%
Dividend rate	—%	—%

Summary of Stock Option Transactions

The following table summarizes stock option transactions issued under the Plans:

	Shares Available for Grant		Number of Options Outstanding		Weighted-Average Exercise Price per Share		Weighted Average Remaining Contractual Term (in years)
Balance at December 31, 2014	606,061		1,072,011		6.34		8.67
Additional shares authorized	270,764
Options granted	(955,713	)	955,713		3.08
Options exercised			(83,848	)	3.50
Options canceled/forfeited	85,037		(85,037	)	5.03
Balance at December 31, 2015	6,149		1,858,839		4.82		8.75
Additional shares authorized	560,717
Options granted	(538,500	)	538,500		1.59
Options exercised			—		—
Options canceled/forfeited	99,700		(99,700	)	2.33
Balance at March 31, 2016	128,066		2,297,639		$	4.09	8.77