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Purpose To compare the variations in ocular torsion measurements made using different fundus photographic methods. Methods We enrolled subjects with three conditions: (1) patients with intermittent exotropia (IXT) (n = 44), (2) patients with unilateral superior oblique palsy (SOP) (n = 10), and (3) normal subjects as controls (n = 85). Ocular torsion was measured by disc-center–fovea angle (DFA) using three different imaging modalities: (1) conventional fundus photography (CFP) with a 45° field of view (FV), (2) wide-field fundus photography (WFP) with a 200° FV, and (3) optical coherence tomography (OCT) with a 55° FV. Results In the IXT group, the DFAs in the right and left eyes were 5.70±3.35° and 6.37±3.36°, respectively, for CFP, 8.39±5.24° and 8.61±3.67° for WFP, and 5.73±3.61° for 6.16±3.50° for OCT. In the SOP group, the DFAs in paretic and nonparetic eyes were 12.19±1.69° and 6.71±1.09°, respectively, for CFP, 14.29±2.36° and 8.23±3.31° for WFP, and 12.12±1.73° and 6.91±1.12° for OCT. In the control group, the DFAs in the right and left eyes were 5.39±2.65° and 5.71±3.16°, respectively, for CFP, 8.77±5.56° and 8.90±6.24° for WFP, and 5.27±2.67° and 5.72±3.20° for OCT. There was no difference between the results from CFP and OCT among the three groups. However, the torsional angle was larger when measured using WFP than the other two photographic methods (CFP and OCT) in all three groups (all p<0.05). Conclusion The ocular torsion measurement varies with the fundus photographic method used to measure it. Clinicians should be careful to avoid overestimating ocular extorsion when it is evaluated using WFP.

We present and discuss theoretical techniques that considerably increase the power of dynamical LEED calculations, particularly i n the layer treatment of surfaces. Their wide applicability makes them especially suitable for surface structural determination. The layer doubling method is an efficient and accurate way of calculating reflectivities off a stack of identical atomic layers requiring only finite absorption for convergence. Layer summation over surface-induced sublattices avoids the repetition of lengthy summations when the surface has a different two-dimensional unit cell than the substrate. The exploitation of symmetry finally can give spectacular reductions in computing time.