Simplifying the Diagnosis of Vertical Diplopia: Is It Skew or Not?

Ocular tilt reaction (OTR) and trochlear nerve palsy (TNP) can induce cyclotorsion. We aimed to assess the utility of fundus photography in distinguishing between these disorders. The database of a neuro-ophthalmology hospital-based clinic was retrospectively searched for patients referred for new-onset vertical diplopia between 2020 and 2023. Medical data were collected, and the angle between the optic disc and fovea was measured using ImageJ software to quantify torsion. Distinct torsional patterns were identified between the groups. OTR was characterized by variable, often conjugate torsion, whereas TNP demonstrated consistent disconjugate extorsion. Analysis of interocular torsional relationships, rather than magnitude alone, provided useful diagnostic discrimination. Fundus photography may be useful for differentiating OTR from TNP in complicated neurological cases, particularly in patients who are difficult to examine. This study emphasizes the practical clinical value of fundus photography as a simple, accessible, and objective tool for differentiating OTR from TNP, by contributing the torsional component of OTR triad, particularly in emergency or diagnostically challenging settings where standard examination may be limited.