The correlation between hypertropia and head tilt in congenital unilateral superior oblique muscle palsy

Purpose: To evaluate the correlation between the angle of deviation in different gazes and the amount of head tilt in patients with congenital unilateral superior oblique muscle palsy (SOP). Methods: This case series study was performed on 20 consecutive SOP patients with head tilt. Based on the Bielschowsky three-step test, the angle of deviation was measured in different gazes. Furthermore, the hypertropia difference between the two lateral gazes (gaze difference) and the two head tilt sides (bilateral head tilt difference) was calculated. For measuring head tilt, close-up pictures from 40 cm with a habitual abnormal head position were captured and analyzed by the Corel Draw X7 software. Results: The mean age of patients was 13 ± 9 years (range, 2.5-31 years). The mean angle of hypertropia in ipsilateral and contralateral head tilt was 24.5 Δ ± 7.1 Δ and 6.5 Δ ± 4.2 Δ, respectively (P < 0.001), and in ipsilateral and contralateral lateral gaze positions, it was 8.2 Δ ± 5.5 Δ and 22.5 Δ ± 6.1 Δ, respectively (P < 0.001). The mean of bilateral head tilt hypertropia difference was 18 Δ ± 5.3 Δ and gaze hypertropia difference was 14.3 Δ ± 6.16 Δ. There was a positive correlation between bilateral head tilt hypertropia difference and the amount of head tilt (R = 0.609, R2 = 0.371, P = 0.004, the amount of head tilt = 0.39 × [Bilateral head tilt hypertropia difference] +1.77). The amount of head tilt also had a positive correlation with the gaze hypertropia difference (R = 0.492, R2 = 0.242, P = 0.028, the amount of head tilt = 0.27 × [gaze hypertropia difference] +4.81). Conclusion: In SOP patients, the amount of head tilt had a positive correlation with bilateral head tilt hypertropia difference and also gaze hypertropia difference.