An adjustable suture is a kind of slip-knot that holds the muscle in place. In eye muscle surgery, these sutures allow an ophthalmologist to readjust the position of the eye after surgery after the patient has had time to wake up from anesthesia. When a patient is asleep during surgery, we can't always tell that the eye has responded to the repositioning of the muscle in the precise way we expect. When the patient wakes from surgery, we might see that the eye isn't exactly where we thought it was. Adjustment is typically performed back in the clinic (same day or within a few days after the initial surgery). Then, with the patient awake, we can pull those slip-knots one way or another to shift the eye muscle position again to redirect the eye. Believe it or not this doesn't usually hurt, but of course, patients are anxious about having sutures adjusted until they've actually been through it and discover that it's not so bad.