Using Layers to Control Retouching

One of the advantages of performing a retouch on an element that has been isolated on a layer, and particularly when you are using a tool such as a Healing Brush tool, is that you can adjust the impact of the tool by adjusting the opacity of the layer on which you have performed the retouch. So if you completely remove a wrinkle with the healing brush, and would like to bring back part of the wrinkle, if you have performed this retouch on a layer you can lower  the opacity of the layer to return as much of it as you like.