Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (30,832)	$ (17,765)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	624	218
Provision for doubtful accounts	255	0
Stock-based compensation	14,728	12,706
Common stock issued in exchange for services		100
Loss on disposal of property and equipment		53
Changes in operating assets and liabilities:
Accounts receivable	(1,058)	(124)
Inventories	(3,874)	(644)
Prepaid expenses and other assets	(1,386)	(8)
Accounts payable	699	(47)
Accrued expenses	2,485	(95)
Deferred revenue	1	(91)
Other liabilities	(150)	174
Net cash used in operating activities	(18,508)	(5,523)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(582)	(547)
Net cash used in investing activities	(582)	(547)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	78,806	10,430
Initial public offering costs	(3,556)
Payments on equipment financing	(82)	(44)
Net cash provided by financing activities	75,168	10,386
NET CHANGE IN CASH AND CASH EQUIVALENTS	56,078	4,316
CASH AND CASH EQUIVALENTS, beginning of year	8,237	3,921
CASH AND CASH EQUIVALENTS, end of year	64,315	8,237
SUPPLEMENTAL DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Settlement of stock-based compensation liability	18,243
Forfeitures of liability-classified awards	1,313
Unpaid property and equipment included in equipment financing	831
Transfer from inventories to property and equipment for demonstration lasers and lasers placed with customers	2,848	377
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash payments for interest	11	4
Cash payments for taxes	$ 5	$ 1