Purpose
We developed a method for quantifying intraoperative torsional forced ductions. We now describe performance of the torsional forced duction test in patients with oblique dysfunction and in controls, using photographic recording and reading of torsional position.
Methods
We studied 25 patients with oblique dysfunction (9 with presumed congenital superior oblique palsy (SOP), 10 with presumed acquired SOP, and 6 with Brown syndrome) and 31 controls (entirely normal forced duction tests prior to planned horizontal muscle surgery). We also studied 3 of these patients while the superior oblique (SO) was disinserted. After induction of deep general anesthesia, the 6 and 12 o’clock positions at the limbus were marked. A Mendez-ring was aligned with these reference marks and a photograph was taken. The limbus was grasped with forceps, the globe was maximally excyclorotated without retroplacement and then maximal incyclorotated, and photographs were taken at each position. Photographs were duplicated for evaluation of test-retest reliability, and maximal excyclorotation and incyclorotation were read (in degrees) by a masked observer. Intraclass correlation coefficients (ICC) and 95% limits of agreement (LOA) were calculated. Maximal excyclorotation and incyclorotation in each oblique dysfunction condition were compared with controls.
Results
Test-retest reliability was excellent with a 95% LOA of 4.4 degrees and an ICC of 0.97. Eyes with presumed congenital SOP had greater maximal excyclorotation than controls (mean±SD, 38.3±10.5 vs 29.3±5.5, p=0.01). Maximal excyclorotation in presumed acquired SOP was similar to controls (27.3±4.7 vs 29.3±5.5, p=0.50). Eyes with Brown syndrome had lower maximal excyclorotation than controls (11.2±6.6 vs29.3±5.5, p=0.0007). Maximal excyclorotation in cases with disinserted SO was greater than controls (52.0±3.5 vs 29.3±5.5, p=0.005). Maximal incyclorotation of presumed congenital SOP, presumed acquired SOP, and Brown syndrome were similar to controls (29.1±6.1, 28.7±4.7, 29.6±10.5 vs 32.5±6.6, all p>0.1).
Conclusions
Photographic reading of the new torsional forced duction test shows excellent test-retest reliability. The torsional forced duction test allows precise assessment of oblique muscle tightness and laxity, and reflects differences between congenital SOP, Brown syndrome, SO disinsertion and controls.