Business Segments - Schedule of Revenue Information by Product (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	$ 9,021	$ 10,595
G6
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	2,923	3,106
Retina
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	4,134	5,599
Other
Entity Wide Information Revenue From External Customer [Line Items]
Total revenues	$ 1,964	$ 1,890