When stage 4 or 5 ROP is reached, the retina is detached and other therapies can be performed. One such therapy is scleral buckling, which involves encircling the eyeball with a silicone band to try and reduce the pulling on the retina. The most commonly performed surgery is vitrectomy (removal of the gel-like substance called the vitreous that fills the back of the eye). Sometimes the removal of the lens as well is required if the retina is touching the back surface of the lens, which would make it impossible to enter the eye.