During LASIK procedure, the shape of the cornea is to be changed. This involves cutting and removing eye tissue that cannot be replaced. Hence changes once made during LASIK are permanent and cannot be reversed. While during Implantable Collamer Lens surgery, the implantable lens is placed in front of the natural lens of the eye, this results in better focusing abilities of the lens which improves vision drastically.
And if at all your prescription changes or you are not too happy with your ICL implant surgery, the lens is replaceable and removable. However, the procedure is not advisable for people with severe eye conditions such as Glaucoma, Diabetic Retinopathy, etc.