Balance Sheets - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 9,040,816	$ 10,796,072
Accounts receivable, net of allowance of $458,701 and $398,847 in 2019 and 2018, respectively	5,239,470	5,021,111
Inventories, net	1,309,134	1,191,666
Prepaid expenses and other current assets	774,014	963,700
Total current assets	16,363,434	17,972,549
Property and equipment, net	328,614	343,693
Operating lease right-of-use assets	5,580,457
Other assets	170,088	198,365
Total assets	22,442,593	18,514,607
Current liabilities:
Accounts payable	2,383,230	1,726,360
Accrued liabilities	2,273,687	2,642,481
Deferred revenue	5,645,815	5,825,536
Current portion of operating lease liabilities	2,159,944
Total current liabilities	12,462,676	10,194,377
Long-term deferred revenue	404,607	407,151
Operating lease liabilities	3,433,430
Other liabilities	813,641	641,461
Total liabilities	17,114,354	11,242,989
Convertible preferred stock:
Convertible preferred stock, par value $0.001; 10,000,000 shares authorized, 23,880 and 23,900 shares outstanding at 2019 and 2018	5,955,354	5,960,475
Stockholders' equity (deficit):
Common stock, par value $0.001; 300,000,000 shares authorized, 59,308,237 and 59,058,297 shares issued at 2019 and 2018, respectively	59,308	59,058
Additional paid in capital	478,363,886	478,179,574
Treasury stock, 4,015 shares at 2019 and 2018	(205,999)	(205,999)
Accumulated deficit	(478,844,310)	(476,721,490)
Total stockholders' equity (deficit)	(627,115)	1,311,143
Total liabilities and stockholders' equity (deficit)	$ 22,442,593	$ 18,514,607