Diagnosis and surgical management of isolated inferior oblique palsy

●AIM:To describe the etiology,clinical characteristics,surgical options and surgical outcomes of isolated inferior oblique palsy(IOP).●METHODS:A retrospective review was performed on patients with isolated IOP who were seen between January 2010 and June 2017.The following clinical data were obtained from the patients’charts:visual acuity,ocular alignment,ocular motility,cyclotorsion,stereoacuity,Parks three-step test,surgical methods,surgical outcomes and complications.Surgical success was defined as horizontal deviation≤10 prism diopters(PD)and a vertical deviation≤5 PD in primary gaze at both near and distant vision as assessed at last follow-up.●RESULTS:The records from a total of 18 patients(8 males and 10 females)with an average age of 27.56 y were included in this study.The right eye was affected in 11 patients,the left in 6 patients and both eyes in 1 patient.Twelve cases(66.7%)were congenital and 6(33.3%)were acquired IOP.The 6 acquired cases involved 2 resulting from orbital trauma/surgery,2 from midbrain microvascular ischemia,1 from myasthenia gravis and 1 of unknown etiology.Strabismus surgery was performed in 13 cases.Surgical techniques included weakening of superior oblique and vertical rectus recession and resection.After a mean follow-up of 15.11 mo,the corrected vertical deviation in primary position was 19.92±8.52 PD(P=0.000)and the corrected horizontal deviation was 14.31±12.68 PD(P=0.002).The surgical success rate was 61.5%and no surgical complications were present.●CONCLUSION:Isolated IOP represents a rare condition,with most cases(66.7%)involving a congenital basis.The acquired cases included vascular,orbital trauma/surgery and myasthenia gravis.Weakening of the ipsilateral superior oblique muscle and/or contralateral superior rectus recession often resulted in favorable surgical outcomes with a surgical success rate of 61.5%.