nice correlation between the objective measures of ocular torsion in this case, as obtained from fundus photography and OCT. Discussion The ability of OCT to measure ocular torsion is based upon its ability to estimate the angle between a line drawn from the optic nerve center to the fovea and the true horizontal plane, called the “disc-fovea angle.”5,9 Previously documented mean normal ranges of cyclotorsion with Spectralis OCT have been reported to be -6.6° ± 2.8°.5 A recent study compared cyclotorsion with Spectralis OCT in normal versus trochlear nerve palsy patients.9 This study reported average cyclotorsion in trochlear nerve palsies of -11.3° (range: -7.7° to 14.9°).9 However, to the author’s knowledge, studies of other OCT platforms to measure cyclotorsion specifically, such as the Cirrus OCT used in this case, do not exist. The Cirrus OCT has a measuring tool within its standard software capable of measuring linear distances (microns). Using this tool to measure the distance from the fovea to the center of the optic nerve, and then measuring a second distance from the fovea along the horizontal meridian to form a right triangle, a clinician could perform a simple trigonometric cosine calculation to estimate the disc-fovea angle. This would then allow the clinician to document the degree of ocular torsion, as in this case (Figure 2). Additionally, the true foveal center can be easily identified on standard OCT macular thickness scans, allowing more accurate ocular torsion measurements. Since the patient was able to alleviate her vertical diplopia with a small head tilt, she declined further treatment beyond monitoring in this case. The patient is being followed on a yearly basis due to the chronicity and stability of her vertical deviation. The patient’s systemic risk factors (i.e., hypertension and diabetes mellitus) account for her stroke history and subsequent trochlear nerve palsy in this case. Given the known anatomy of the trochlear nerves, the likely lesion location in this case is either the inferior dorsal midbrain (at the level of the inferior colliculus) or further along the trochlear nerve’s course towards the superior oblique muscle, involving the nerve’s vasa-nervorum blood supply.10 Conclusion Cirrus OCT platforms, along with some basic trigonometric calculations, can provide an objective Optometry & Visual Performance 127 Volume 14 | Issue 2 | June 2026 means to estimate degrees of cyclotorsion in acquired ocular torsion disorders, such as this case of trochlear nerve (CN IV) palsy. This is important since some patients are subjectively poor responders to classic tests that measure ocular torsion, such as the double Maddox rod. OCT has the potential to provide objective measures of ocular torsion that do not depend on patients’ subjective responses. Potential OCT software development and future study regarding the use of OCT in these ocular torsion disorders is needed and should be encouraged. References 1. Borgman CJ, Haynes JA. Measuring acquired ocular torsion with optical coherence tomography. Clin Exp Optom 2021;104:132-4. 2. Roh YR, Hwang JM. Comparison of subjective and objective torsion in patients with acquired unilateral superior oblique muscle palsy. Br J Ophthalmol 2011;95:1583-7. 3. Sharpe JA, Kumar S, Sundaram AN. Ocular torsion and vertical misalignment. Curr Opinion Neurol 2011;24:18-24. 4. Lee JJ, Chun KI, Baek SH, Kim US. Relationship of hypertropia and excyclotorsion in superior oblique palsy. Korean J Ophthalmol 2013;27:39-43. 5. Lengwiler F, Rappoport D, Jaggi GP, Landau JK, et al. Reliability of cyclotorsion measurements using scanning laser ophthalmoscopy imaging in healthy subjects: The CySLO study. Br J Ophthalmol 2018;102:535-8. 6. Borgman CJ, Follansbee CJ. Degree of excyclotorsion in an acquired trochlear nerve palsy. Clin Exp Optom 2020;103:550-1. 7. Sophocleous S. Use of optical coherence topography for objective assessment of fundus torsion. BMJ Case Rep 2017:bcr2016216867. 8. Kanku MS, Sele S, Held U, et al. Cyclotorsion measurement on scanning laser ophthalmoscopy imaging compared with fundus photography in patient with fourth nerve palsy and healthy controls: CySLO-IV study. J Neuroophthalmol 2021;41(4):e612-e618. 9. Amini N, Nowroozizadeh S, Cirineo N, Henry S, et al. Influence of the disc-fovea angle on limits of RNFL variability and glaucoma discrimination. Invest Ophthalmol Vis Sci 2014;55:7332-42. 10. Morillon P, Bremner F. Trochlear nerve palsy. Br J Hosp Med 2017;78:C38-C-40. Correspondence regarding this article should be emailed to Christopher J. Borgman, OD, at cborgman@sco.edu. All statements are the author’s personal opinions and may not reflect the opinions of the representative organization, OEPF, Optometry & Visual Performance, or any institution or organization with which the author may be affiliated. Permission to use reprints of this article must be obtained from the editor. Copyright 2026 Optometric Extension Program Foundation. Online access is available at www.oepf.org and www.ovpjournal.org. Borgman CJ. Objectively measuring acquired ocular torsion secondary to trochlear nerve palsy with Zeiss cirrus optical coherence tomography. Optom Vis Perf 2026;14(2):125-7.
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