Purpose: This study was designed to analyze the consecutive overaction of the contralateral inferior oblique (IO) muscle after unilateral weake in procedure of the same muscle which is a well-known but not regularly studied phenomenon.
Material and methods: Unilateral weakening of overactive IO muscle was performed in a group of 27 patients with esotropia (14 recessions and 13 marginal myotomias). Eleven of these patients had unilateral overaction of the IO muscle. In the remaining 16 patients the overaction was highly asymmetric.
Results: Postoperatively we observed only one consecutive overaction of the contralateral IO in patients with unilateral overaction. However, this condition was observed in 11 of 16 patients with asymmetric IO overaction.
Conclusion: The innervational pathogenesis of this phenomenon is a subject of discussion. The authors emphasize the necessity of the clinical examination in order to identify the bilateral asymmetric forms and to neutralize them by convenient surgical procedures.