The injection of Botox into an extraocular muscle produces a dose-dependent duration of paralysis of that muscle. The injection is given under electromyography positional control using a monopolar electrode needle. The toxin is tightly bound to the muscle tissue. The doses are so small that systemic toxicity does not occur. Several days after the Botox injection the chemical paralysis of the muscle allows the eye to be moved into the field of action of the antagonist muscle. During the time the eye is deviated. The chemically paralysed muscle is stretched, whereas the antagonist muscle is contracted. As the paralysis resolves, the eye will gradually return toward its original position but with a new balance of forces that may reduce or eliminate the deviation. Two or more injections are often necessary to obtain a lasting effect.