The modern technique of cataract surgery involves removing the cloudy contents of the eye's natural lens, while leaving the clear outer membrane, called the capsule, to hold the new intraocular lens in place.
The capsule has cells on it which will, in some cases, continue to produce lens fibers. These fibers will form little beads or "pearls" on the lens capsule, forming a secondary membrane. When these pearls accumulate in the visual axis, they cause a blurring of vision similar to that which one experiences with a cataract. Six out of ten people who have cataract surgery will eventually develop a cloudiness of this membrane.
If the clouding of the posterior capsule interferes with your vision, your doctor may suggest opening the capsule to restore normal sight. This is done with a procedure called YAG laser capsulotomy, where your doctor uses a laser beam to make an opening in the posterior membrane to let light pass through and restore clear vision. This is a painless outpatient procedure and there are no restrictions following the laser. Patients usually notice an improvement in vision the next day.