Parks Three-Step Test

Identify the paretic cyclovertical muscle in isolated vertical strabismus.

Three-Step Assessment

Eye × Gaze × Tilt

1.Which eye is hypertropic in primary gaze?

2.Is the hypertropia worse in right or left gaze?

3.Is the hypertropia worse with right or left head tilt?

Affected Muscle

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Reference

Parks MM. Isolated cyclovertical muscle palsy. AMA Arch Ophthalmol. 1958;60(6):1027–1035.