RESUMEN
Overaction of the inferior oblique muscles is the most common clinical form of the motility disturbance of oblique muscles which has been rarely studied in Vietnam. 150 patients aged of 4years old and older suffered from strabismus with disturbance of the oblique muscles (78.6% of them had overaction of the inferior obliquemuscle) were studied in National Institute of Ophthalmology. Objectives: to identify the clinical forms and characteristics, to evaluate the results of operation. Method: This study was designed belongs to prospective clinical trial in hospital. The operated patients were observed and evaluated during 2 years after surgery divided into three terms (short term, medium and long term). The results of surgery was optimistic. Conclusion: overaction of the inferior oblique is a clinical form of motility disturbance of the oblique muscles having the best surgical results.