The "Fadenoperation" creates an artificial paresis, the effect of which increases in the field of action of the muscle operated upon. The postoperative effect on eye position and motility was studied in order to find the typical curve of influence upon the angle in different directions of gaze. In esotropia a fixation of the medial rectus muscle 13 mm behind its insertion will create an average angle reduction of 4 degrees in the primary position of gaze and 12 degrees (9 degrees long-term) in lateral gaze with the operated eye adducted. - Fadenoperations cause a reduction of (overacting) convergence (non-accomodative), adduction, and changing angle. The paper deals with the majority of patients who show overacting convergence and changing angles but lack an increasing angle in version movements. This means that in lateral gaze overcorrection may occur: From the curve of angle reduction the surgeon can derive a slight exponential decrease of each of the three partial functions. Fadenoperation, therefore, will suit well in patients showing overactions of all three components, but will bring "side effects" in cases which lack one or two of these dysfunctions. Bilateral Fadenoperations produce a minor incomitance pattern.