Disaggregation of Sales, Geographic Sales and Product Sales - Net Sales by Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Oct. 02, 2020	Sep. 27, 2019
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 5,588	$ 5,240	$ 15,901	$ 15,269
Total net sales	47,081	39,055	117,462	111,302
ICLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	41,493	33,815	101,561	96,033
IOLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	3,325	4,093	9,880	11,984
Other surgical products [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 2,263	$ 1,147	$ 6,021	$ 3,285