The Company’s net sales are generated primarily from sales of iStent products to customers, and following the Avedro Merger on November 21, 2019, sales of Photrexa and associated drug formulations as well as KXL and Mosaic systems. Customers are primarily comprised of ambulatory surgery centers, hospitals and physician private practices, with distributors being used in certain international locations where the Company currently does not have a direct commercial presence.

Revenue is recognized in an amount that reflects the consideration the Company expects to be entitled to in exchange for goods or services, and all of the Company’s net sales are considered revenue from contracts with customers.

The Company’s revenues disaggregated by product category, for the three and six months ended June 30, 2020 and June 30, 2019 was as follows (in thousands):


	Three months ended				Six months ended
	June 30,				June 30,
	2020		2019		2020		2019

Glaucoma	$	24,948	$	58,600	$	69,081	$	112,626
Corneal Health		6,610		—		17,813		—
Total	$	31,558	$	58,600	$	86,894	$	112,626

The following table presents the Company’s revenues disaggregated by geography for the three and six months ended June 30, 2020 and June 30, 2019 (in thousands):


	Three months ended				Six months ended
	June 30,				June 30,
	2020		2019		2020		2019
United States	$	24,169	$	48,088	$	65,553	$	92,305
International		7,389		10,512		21,341		20,321
Total net sales	$	31,558	$	58,600	$	86,894	$	112,626

Amounts are recorded as accounts receivable when the Company’s right to consideration becomes unconditional. Payment terms on invoiced amounts are typically 30 days for glaucoma and corneal health products, though extended payment terms on corneal health products may be offered. However, the Company does not consider any significant financing components in customer contracts given the expected time between transfer of the promised products and the payment of the associated consideration is less than one year. As of June 30, 2020 and December 31, 2019, all amounts included in accounts receivable, net on the condensed consolidated balance sheets are related to contracts with customers.

Sales commissions earned on U.S. sales of KXL systems are capitalized as the commissions represent costs to obtain a contract and the amortization period is deemed greater than one year. These costs are deferred in other assets on the Company’s condensed consolidated balance sheet, net of the short term portion included in prepaid assets and other current assets, and are amortized as a sales and marketing expense on a straight-line basis over the expected period of benefit. Capitalized sales commissions and the related amortization expense included in the condensed consolidated financial statements were immaterial as of June 30, 2020 and December 31, 2019.

Aside from the aforementioned contract assets, the Company does not have any contract assets given that the Company does not have any unbilled receivables and sales commissions on other products are expensed within selling, general and administrative expenses within the condensed consolidated statement of operations when incurred as any incremental cost of obtaining contracts with customers would have an amortization period of less than one year.

Contract liabilities reflect consideration received from customers’ purchases allocated to the Company’s future performance obligations.

The Company has a performance obligation to issue a rebate to customers who may be eligible for a rebate at the conclusion of their contract term. This performance obligation is transferred over time and the Company’s method of measuring progress is the output method, whereby the progress is measured by the estimated rebate earned to date over the total rebate estimated to be earned over the contract period. The Company’s rebate allowance is included in accrued liabilities in the condensed consolidated balance sheets and estimated rebates accrued were not material during the periods presented.

Additionally, in the U.S. the Company has a performance obligation related to its customers’ right to a future discount on single dose pharmaceutical purchases, and, to a lesser extent, extended warranty service contracts. The amount allocated to the customers’ right to a future discount is expected to be recognized when the customer elects to utilize the discount, which is generally within one year. As of June 30, 2020 and December 31, 2019, this amount was immaterial as was the amount allocated to extended warranty service contracts.

During the three and six months ended June 30, 2020 and June 30, 2019, the Company did not recognize any revenue related to material changes in transaction prices regarding its contracts with customers and did not recognize any material changes in revenue related to amounts included in contract liabilities at the beginning of the period.

The Company’s net sales within a fiscal year may be impacted seasonally, as demand for U.S. ophthalmic procedures is typically softer in the first quarter and stronger in the fourth quarter of a given year.