Abstract
PurposeWe present a novel variation of the traction test of the inferior oblique (IO) muscle. We demonstrate the correlation between the traction test and clinically graded IO overaction and describe the utility of this test to confirm IO weakening.MethodsWe performed a retrospective chart review on all patients who underwent IO surgery and intraoperative intorsion traction tests by a single surgeon over a 10-year period. We compared the traction test results, in 'clock hours' of freedom, before and after IO surgery. We correlated the torsion test at start of surgery with clinical observed IO overaction (scale 0 to +4) in 67 IO operations (56 myectomies, 6 anterior transpositions, 4 myotomies, and 1 recession) and compared to a control group of 23 eyes with minimal or no IO overaction.ResultsThe mean intorsion freedom in the eyes undergoing IO surgery was less than in control eyes (1.63 vs 1.89 clock hour; P<0.00005). There was a significant inverse relationship between grading of clinical IO action and the intorsion test result (Pearson rank coefficient, (r=-0.45; P<0.00001)). Myectomy produced the greatest change in torsion freedom (mean 1.32 clock hour), with all myectomies showing at least 1 clock hour extra freedom after the surgery.ConclusionsThe intorsion traction test confirmed that the IO stiffness correlated with pre-operative IO overaction grade. While it can be helpful in confirming that the entire IO muscle was weakened, it does not substitute for the careful inspection at the end of surgery to ensure there are no remaining IO fibers.