Management of hypotropia in severe traumatic third nerve palsy using superior transposition of the horizontal rectus muscles

Abstract Background Severe traumatic third nerve palsy may cause combined exotropia (XT), hypotropia, ptosis, and marked ocular motility limitation. We describe two individualized combined surgical strategies, each including Knapp-type superior transposition of the horizontal rectus muscles, used to address hypotropia. Case presentation A 27-year-old man with chronic traumatic left third nerve palsy and residual adduction had XT 40 prism diopters (PD) and hypotropia 30 PD on preoperative synoptophore assessment. He underwent an augmented Knapp-type procedure (full-tendon superior transposition of both horizontal recti with posterior augmentation sutures) combined with 6-mm LR recession and 6-mm medial rectus resection. At 9 months, residual XT and hypotropia each measured 6 PD, and he denied diplopia. A 27-year-old woman with chronic traumatic right third nerve palsy had XT 55 PD, hypotropia 25 PD, and an eye held in a depressed position. Forced-duction testing showed mild restriction to passive elevation. She underwent 6-mm inferior rectus recession and augmented full-tendon superior LR transposition (a single-muscle augmented Knapp-type procedure), followed by fellow-eye horizontal rectus surgery for persistent XT. At 5 months after the second operation, visual acuity was 20/20 in both eyes, XT measured 25 PD, and vertical deviation was 0 PD; the eye reached primary position, but active elevation was not restored (elevation −4). Horizontal diplopia persisted, without vertical or torsional diplopia. Double Maddox rod testing showed no subjective torsion, and fundus photography showed no objective torsion. Conclusions These cases illustrate individualized combined surgical strategies, each including Knapp-type superior transposition of the horizontal rectus muscles, that were followed by correction or reduction of primary-position hypotropia. Active elevation was not restored, and the contribution of transposition cannot be separated from that of the concurrent procedures. The observations are hypothesis-generating and do not establish a treatment algorithm, deviation threshold, or superiority over other procedures.