SECONDARY HYPERFUNCTION OF THE CONTRALATE RAL INFERIOR OBLIQUE MUSCLEAFTER THE UNILATERAL INFERIOR OBLIQUE WEAKENING PROCEDURE

Purpose This study was designed to analyze the consecutive overaction of the contralateral inferior oblique (IO) muscle after unilateral wea ke in procedure of the same muscle which is a well-known but not regul arly studied phenomenon.Material and methods Unilateral weakening of o veractive IO muscle was performed in a group of 27 patients with esotr opia (14 recessions and 13 marginal myotomias). Eleven of these patien ts had unilateral overaction of the IO muscle. In the remaining 16 pat ients the overaction was highly asymmetric. Results Postoperatively we observed only one consecutive overaction of the contralateral IO in p atients with unilateral overaction. However, this condition was observ ed in 11 of 16 patients with asymmetric IO overaction. Conclusion The innervational pathogenesis of this phenomenon is a subject of discussi on. The authors emphasize the necessity of the clinical examination in order to identify the bilateral asymmetric forms and to neutralize th em by convenient surgical procedures.