Knapp procedure in the treatment of double elevator palsy

Abstract

Objective To investigate the efficacy of Knapp procedure in the treatment of double elevator palsy. Methods Fifteen patients with congenital double elevator palsy underwent Knapp procedures and retrospective analysis of the preoperative and postoperative vertical deviation in the primary position, ocular motility, and binocular vision. Results The average vertical deviation in the primary position was 34.67 ± 8.55 prism diopters (PD) before surgery and 6.53 ± 6.50 PD after surgery (P <0.05). The average corrected vertical deviation was 28.13±3.58 PD. The average preoperative upgaze was -3.73±0.70 and postoperative upgaze was -1.8±0.77 (P <0.05). The mean improved upgaze was 1.93 ± 0.59. Mild limitation in downgaze (mean-0.80 ± 0.41) presented after operation. Five patients having binocular vision with abnormal head posture (AHP) before surgery obtained binocular single vision in the primary position and reading position after operation. After surgery AHPs disappeared or reduced to less than 5°. The surgical outcomes were satisfied in 73.3% patients. But the patients with ≥40 PD preoperative vertical deviation were under corrected and needed the secondary operations. Conclusions Knapp procedure is an efficient procedure for treatment of double elevator palsy without restriction of ipsilateral inferior rectus. It can obviously correct the vertical deviation in the primary position and improve upgaze, which is good to obtain the binocular single vision in the primary and reading position. Key words: Double elevator palsy; Muscle transposition; Knapp procedure; Ocular movement