Optometry & Visual Performance 125 Volume 14 | Issue 2 | June 2026 Article • Objectively Measuring Acquired Ocular Torsion Secondary to Trochlear Nerve Palsy with Zeiss Cirrus Optical Coherence Tomography Christopher J. Borgman, OD • Southern College of Optometry • Memphis, Tennessee Introduction Abnormal cyclotorsion has been known to occur with acquired ocular torsion disorders such as trochlear nerve palsies and skew deviations.1-5 Historically, the most common way to measure ocular torsion objectively has been with fundus photography.2-5 Newer reports document OCT as another tool to measure objective ocular torsion in acquired cases.1,6-8 This case expands on previous OCT ocular torsion reports using Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany)1,6,8 to include Cirrus OCT (Carl Zeiss Meditec, Dublin, California, USA) as a potential way to assess acquired ocular torsion disorders. Case Report A 68-year-old female presented for routine eye examination, with a chronic vertical diplopia complaint for five years since she suffered a brainstem stroke secondary to her history of hypertension and diabetes mellitus. Her diplopia disappeared when covering either eye, suggesting binocular vision dysfunction. She was able to alleviate her diplopia fully in primary gaze with a small left head tilt. Her medical history included hypertension and osteoporosis. Visual acuity was 20/20 OD and 20/25 OS. Pupils, extraocular motilities, and confrontation visual fields were normal OU. Cover test revealed a 2Δ hyper deviation OD. With the Parks-Bielschowsky three-step test, the hyper deviation worsened with right head tilt and in left gaze, suggesting right superior oblique weakness.1,2,4 External examination was unremarkable OU. Retinal examination was unremarkable except for mild macular drusen OU. Increased excyclotorsion (-11°) of the right eye and normal torsion (-4°) of the left eye were noted objectively with fundus photography, consistent with a mild trochlear nerve palsy OD (Figure 1). Cirrus OCT macular thickness scans were also performed on the patient OU. Using the linear measuring tool embedded within the Cirrus OCT software, two linear micron measurements were drawn: one from the center of the optic nerve to the fovea, and the second to estimate the horizontal meridian. Using these linear OCT measurements, the disc-to-fovea angle was calculated to estimate the amount of ocular torsion present in each eye (-11.4° OD, -6.6° OS; Figure 2). This shows a Christopher J. Borgman, OD Memphis, Tennessee Associate Professor, SCO BA, 2006, Central College, Pella, Iowa OD, 2010, Illinois College of Optometry, Chicago, Illinois Residency, 2011, Primary Care and Ocular Disease, Illinois College of Optometry Fellow of the American Academy of Optometry ABSTRACT Background: Optical coherence tomography (OCT) allows the identification of key fundus landmarks (fovea and center of optic disc) to help calculate estimated ocular torsion amounts in acquired ocular torsion disorders. A case of chronic trochlear nerve (CN IV) palsy secondary to stroke, in which objective ocular torsion was measured with OCT software and basic trigonometric calculations, follows in this report. Case Report: A 68-year-old female patient with a history of brainstem stroke from five years earlier showed a right-eye hyper deviation of 2Δ. Resultant Parks-Bielschowsky three-step testing, as well as ocular torsion testing with OCT software measurements, helped determine that the patient’s hyper deviation was secondary to a right CN IV palsy. Her objective ocular torsion was calculated using measurement tools and trigonometric functions derived from her OCT scans. Conclusions: OCT technology can provide objective methods for measuring ocular torsion in acquired ocular torsion disorders. Potential OCT software development and future study regarding the use of OCT in these ocular torsion disorders is needed. Keywords: ocular torsion, optical coherence tomography, trochlear nerve palsy
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