Business Segments - Schedule of Revenue Information by Product (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Oct. 02, 2021	Sep. 26, 2020	Oct. 02, 2021	Sep. 26, 2020
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues		$ 13,264	$ 8,803	$ 38,649	$ 24,043
Cyclo G6
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues		3,145	2,776	10,093	7,812
Retina
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues		7,777	4,429	22,012	11,171
Other
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	[1]	$ 2,342	$ 1,598	$ 6,544	$ 5,060

[1] Includes service contract revenues of $387 and $302 and $1,061 and $929 recognized during the three and nine months ended October 2, 2021 and September 26, 2020, respectively. Includes $228 and $339 recognized revenue related to the exclusive distribution rights during the three and nine months ended October 2, 2021, respectively. Other also includes revenues from paid service, royalty, freight and legacy G probes.