Geographic and Product Data (Details 1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Sep. 29, 2017	Sep. 30, 2016
Product Information [Line Items]
Net sales	$ 23,473	$ 20,052	$ 65,759	$ 60,295
ICLs [Member]
Product Information [Line Items]
Net sales	18,110	14,801	49,698	43,389
IOLs [Member]
Product Information [Line Items]
Net sales	3,892	4,649	12,875	14,783
Other surgical products [Member]
Product Information [Line Items]
Net sales	$ 1,471	$ 602	$ 3,186	$ 2,123