Business Segments - Schedule of Revenue Information by Product (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues		$ 6,219	$ 10,426	$ 15,240	$ 21,021
Cyclo G6
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues		2,113	3,351	5,036	6,457
Retina
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues		2,608	5,248	6,742	10,847
Other
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	[1]	$ 1,498	$ 1,827	$ 3,462	$ 3,717

[1] Includes service contract revenues of $311 and $296 and $627 and $604 recognized during the three and six months ended June 27, 2020 and June 29, 2019, respectively. Other also includes revenues from paid service, royalty, freight and legacy G probes.