A Novel Use of Optical Coherence Tomography for the Assessment of Ocular Torsion

Abstract

Abnormal ocular torsion is most frequently the result paresis of the fourth cranial nerve. The presence of torsion can be a barrier to fusion, in which case, surgical intervention is required for a patient to have single vision. Clinically, ocular torsion can be measured either subjectively or objectively, the latter traditionally using the relationship between the fovea and the optic disc. However, previous literature has shown inconsistencies between torsion a patient’s perceived subjective torsion, and the amount of anatomical fundus torsion. Therefore, the aim of the current study was to investigate the relationship of subjective and objective ocular torsion in patients with cranial nerve four palsies, and more specifically a potentially novel objective method using the retinal raphe. The subjective tests used in this study were modified Bagolini Lenses, Double Maddox Rods, the Synoptophore, and the Harms Tangent Screen. The three objective tests used were fundus photographs, optical coherence tomography using Bruch’s membrane opening, and the temporal raphe. The first two methods used the traditional relationship between the fovea and optic disc. The current study also assessed the relationship of these measuring methods to the Subjective Horizontal. The results of this study found that the torsional angle measured by subjective tests was not significantly different than the objective angles of the fovea-optic nerve relationship or the temporal raphe when accounting for the physiological position of the retina. The current study also found that the Subjective Horizontal of participants with cranial nerve four palsies was significantly different than the subjective and objective tests, except for the temporal raphe. Therefore, it was concluded that the previously reported significant differences between subjective torsion and the fovea-optic nerve angles may not take the physiological retinal position into account. It was also concluded that participants with long-standing cranial nerve four palsies were on a spectrum of adaption and that the Subjective Horizontal adjusts to the orientation of the temporal raphe.