Disaggregation of Revenues, Geographic Sales and Product Sales - Revenue from External Customers by Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 4,797	$ 5,935
Total net sales	32,583	27,093
ICLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	27,786	21,158
IOLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	4,017	4,058
Other surgical products [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 780	$ 1,877