In most cases, when cataracts are removed, the front portion of the capsule of the lens is removed, the contents of the lens
is suctioned out, and the back capsule called the posterior capsule is left in place. This is done because it is safer for
the retina, and in most cases will help support an intraocular lens implant. The capsule is purposely left intact in spite
of the fact that it will often cloud in time. Sometimes this clouding occurs within months of surgery, but in most cases it
is within a 3-4 year period. This clouding of the posterior capsule is called secondary membrane or simply an after
cataract. It is not exactly a cataract, but it does act in the same manner. When the vision is affected significantly by
this membrane, the YAG laser is often used to open a small hole in the center.
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