Disaggregation of Sales, Geographic Sales and Product Sales - Net Sales by Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Jun. 28, 2019	Jun. 29, 2018
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 5,232	$ 6,613	$ 10,029	$ 12,548
Total net sales	39,664	33,905	72,247	60,998
ICLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	34,432	27,292	62,218	48,450
IOLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	3,874	4,186	7,891	8,244
Other surgical products [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 1,358	$ 2,427	$ 2,138	$ 4,304