The formation of layer of scar-like tissue or capsule around an implant is a normal process. However in some patients this layer becomes thick or hard. In order to compare patients a system has evolved to compare the feeling and appearance of the breast after augmentation. This system is called the Baker Classification and is widely used by plastic surgeons.
Class I: the breast feels the same as the normal breast with no hardness or change in shape
Class II: the breast is harder and although the implant is not visible it can usually be felt
Class III: the breast is firm and the implant can be seen. The shape of the breast is usually distorted.
Class IV: the breast is hard and tender and the shape very abnormal.