Clinical Assessment of Ocular Torsion

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Abstract
Abnormal ocular torsion is often missed by indirect ophthalmoscopy because of disorientation or inattention to the normal relationship of the optic disc and fovea. The fovea should be level within the upper third of the disc in the indirect ophthalmoscope view. The amount of abnormal torsion may be estimated using a grading system from “trace” to “4+,” with 4+ indicating a one-half disc diameter displacement of the fovea from its normal range. The normal range of torsional position is approximately 9° in angular extent. Abnormal anatomical torsion may be estimated by indirect ophthalmoscopy, and measured by fundus photography or blind spot mapping. It must be distinguished from subjective torsion as measured by the double Maddox rod test, Lancaster red-green test, or other subjective tests. Sensory adaptations can occur to abnormal torsion, especially in children, enough to reduce or completely eliminate subjective torsion, while anatomical torsion persists. Abnormal ocular torsion occurs with paretic, overacting, or contracted cyclovertical muscles. Abnormal ocular torsion generally does not occur with dissociated vertical deviation or with pseudo-overaction of the obliques. Abnormal ocular torsion is most useful for its diagnostic value in cyclovertical strabismus, but only then when it is anticipated and recognized.

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