Disaggregation of Revenues, Geographic Sales and Product Sales - Net Sales by Products and Services (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 01, 2021	Oct. 02, 2020	Jul. 03, 2020	Apr. 03, 2020	Jan. 03, 2020	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Jan. 01, 2021	Jan. 03, 2020	Dec. 28, 2018
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax									$ 22,053	$ 20,863	$ 22,872
Total net sales	$ 45,998	$ 47,081	$ 35,194	$ 35,187	$ 38,883	$ 39,055	$ 39,664	$ 32,583	163,460	150,185	123,954
ICLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax									141,407	129,322	101,082
IOLs [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax									13,574	15,689	16,193
Other surgical products [Member]
Product Information [Line Items]
Revenue from contract with customer, excluding assessed tax									$ 8,479	$ 5,174	$ 6,679