A secondary membrane is the clouding of the lens capsule after cataract surgery. Many patients experience similar visual symptoms they experienced when they had a cataract. The causes of secondary membranes is unknown. However, if the clouding inhibits your activities of daily living, a capsulotomy may be performed. A capsulotomy involves using a yttrium aluminum garnet laser (YAG laser) to focus on the posterior lens capsule. The laser creates a perforation in the capsule, the capsule moves off to the side and you are able to see clearly again.