When we perform cataract surgery, we take the cataract out of its capsule and then use the capsule as a way to stabilize the lens implant. Sometimes we use a different word for the capsule, which is “bag.” Sometimes we even call it a “capsular bag.”
The capsule is behind the colored iris of the eye and contains the cataract. There is a space behind the back of the iris and in front of the capsule, which is called the sulcus. This is actually another part of the eye that can be used to hold an intraocular lens implant! Generally, we prefer to place the lens implant inside the capsule, but the sulcus can be used in the right setting with the right implant.