It has bought Peter Fernie opticians in Clarkston, East Renfrewshire, and Occuleye in Helensburgh bringing its total number of sites to 27. In December 2012 Black & Lizars acquired Kigour, which had premises in Ayr and Troon.
Mark Ross, chief executive, said the four most recent additions have a combined turnover of £3m. The company has also added Optos Daytona retinal imaging devices.
Mr Ross added: "We will continue to expand our practice network in a carefully controlled manner, as other loss-making optical firms are contracting in the face of difficult market conditions."