Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (25,070)	$ (36,045)
Adjustments to reconcile net loss to net cash used in operating activities:
Gain on sale of discontinued operations	(3,473)
Gain on extinguishment of PPP promissory note	(2,023)
Stock-based compensation	2,237	4,082
Depreciation and amortization	1,565	2,365
(Gain) loss on sales and disposals of property and equipment	(550)	99
Provision for credit losses	47	180
Changes in operating assets and liabilities:
Accounts receivable, net	42	368
Inventories	(197)	352
Prepaid expenses and other assets	150	642
Accounts payable	627	(961)
Accrued expenses	(390)	1,706
Deferred revenue	(234)	(774)
Other liabilities	(356)	(318)
Net cash used in operating activities	(27,625)	(28,304)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sale of discontinued operations	3,700
Payment of fees related to sale of discontinued operations	(227)
Proceeds from sales of property and equipment	594
Purchases of property and equipment	(265)	(67)
Proceeds from maturities of available-for-sale securities		16,000
Net cash provided by investing activities	3,802	15,933
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock and warrants, net of placement agent fees	15,528	19,887
Payment of offering costs related to the issuance of common stock and warrants	(375)	(770)
Repayment of equipment financing	(265)	(293)
Proceeds from purchases under employee stock purchase plan	74	42
Proceeds from PPP promissory note		2,000
Proceeds from issuance of common stock in connection with the exercise of warrants		827
Net cash provided by financing activities	14,962	21,693
NET CHANGE IN CASH AND CASH EQUIVALENTS	(8,861)	9,322
CASH AND CASH EQUIVALENTS, beginning of year	23,906	14,584
CASH AND CASH EQUIVALENTS, end of year	15,045	23,906
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Unpaid property and equipment	17
Transfer of lasers from inventories to property and equipment		207
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash payments for interest	2	$ 28
Cash payments for income taxes	$ 2