Head position-dependent changes in ocular torsion and vertical misalignment in skew deviation.

Area of Science:

• Ophthalmology
• Neuroscience
• Clinical Diagnostics

Background:

• Skew deviation and trochlear nerve palsy are common causes of vertical misalignment and ocular torsion.
• Differentiating between these conditions can be challenging using traditional clinical tests.

Purpose of the Study:

• To determine if ocular torsion and vertical misalignment differ between upright and supine positions in skew deviation.
• To compare these positional changes with those observed in trochlear nerve palsy.

Main Methods:

• Prospective recruitment of patients with skew deviation (n=10), trochlear nerve palsy (n=14), and healthy controls (n=12).
• Measurement of ocular torsion (double Maddox rods) and vertical misalignment (prism and alternate cover test) in both upright and supine positions.

Main Results:

• Patients with skew deviation showed a substantial decrease in ocular torsion (83%) and vertical misalignment (74%) when moving from upright to supine.
• In contrast, patients with trochlear nerve palsy and healthy subjects exhibited minimal changes in torsion and misalignment between positions.
• Statistical analysis confirmed significant differences between groups (P < .001).

Conclusions:

• Positional changes in ocular torsion and vertical misalignment can help differentiate skew deviation from trochlear nerve palsy.
• A decrease in these parameters in the supine position suggests skew deviation.
• Stable parameters between positions indicate trochlear nerve palsy, supporting the 3-step test.