Does Decreased Static Ocular Counter Rolling Account for Bielschowsky Head Tilt Test in Unilateral Superior Oblique Palsy?

Purpose: To understand the relationship of static ocular counter rolling (s-OCR) and clinical manifestations in acquired unilateral superior oblique palsy subjects during the Bielschowsky head tilt test. Methods: Nineteen subjects that were diagnosed with acquired unilateral superior oblique palsy were included. Fundus photographs were obtained at different head tilt angles to evaluate static ocular counter rolling using a fundus camera with a cervical range of motion device. Using a graphics editing program, we calculated s-OCR from fundus photography. Results: The incycloductional s-OCR (OCR-I) in the paretic eye was significantly smaller than the OCR-I in the fellow eye (P = 0.02, <0.001, 0.002 for 10°, 20°, and 30°, respectively, paired t-tests). In contrast, the excycloductional s-OCR (OCR-E) showed no significant difference between the paretic eye and the fellow eye for all angles. There was a significantly positive correlation between the amplitude of OCR-I in the paretic eye and the degree of hypertropia on ipsilesional head tilt (ρ = 0.612, 0.679, 0.474, P = 0.02, 0.002, 0.07 for 10°, 20°, and 30° respectively, Spearman's correlation). The amplitude of OCR-I in the paretic eye also showed a positive correlation with head tilt test difference, which is the degree of hyperdeviation difference between ipsilesional and contralesional head tilts (ρ = 0.445, 0.694, 0.579, P = 0.09, 0.002, 0.024 for 10°, 20°, and 30° respectively, Spearman's correlation). Conclusions: In unilateral SOP, OCR-I in the paretic eye was smaller than that in the fellow eye, and this was positively associated with the degree of hypertropia during ipsilesional head tilting, as well as the head tilt test difference.