Usefulness of magnetic resonance imaging in a patient with diplopia after cataract surgery

Abstract

Dear Editor, Binocular diplopia after cataract surgery could develop in patients with previously unrecognized cranial nerve palsy [1][2][3]. We found a 77-year-old man who developed diplopia for the first time in his life after bilateral phacoemulsification under topical anesthesia.A 77-year-old man with no history of strabismus or diplopia presented with persistent diplopia that developed after cataract surgery and persisted for over the 6 months after cataract surgery. Phacoemulsification and posteriorchamber intraocular lens implantation with a clear corneal incision were performed under topical anesthesia in the left eye; these procedures were performed in the right eye 5 weeks later at a local clinic. Bridle suture was not placed in either of the eyes. Subconjunctival gentamicin and subTenon's dexamethasone were administered inferotemporally. There was no past medical history of head trauma and no family history of strabismus.On examination, visual acuity was 20/20 in both eyes. He showed a head tilt to the left, and asymmetric face with the right fuller face. He had exotropia of 25 prism diopters (PD) and right hypertropia of 16 PD in the primary position, exotropia of 20 PD and right hypertropia of 16 PD in the right gaze, and exotropia of 25 PD and right hypertropia of 25 PD in the left gaze. With the head tilt to the right, he showed exotropia of 30 PD and right hypertropia of 18 PD, and with head tilt to the left, exotropia of 20 PD and right hypertropia of 16 PD. He showed right superior oblique underaction and inferior oblique overaction (Fig. 1).Magnetic resonance (MR) imaging by using a 3-Tesla system (Intera Achieva; Philips, Best, The Netherlands) with T2-weighted imaging of the orbit and high-resolution imaging of the cranial nerves in the brain stem was performed as previously described [4]. Severe hypoplasia of the right superior oblique muscle was observed (Fig. 2a-c), and the right trochlear nerve was not identified in the perimesencephalic cistern (Fig. 2d-f).Binocular diplopia after the cataract surgery could be attributable to the method of anesthesia [1-3]. Extraocular muscle damage may be the most common cause of binocular diplopia after local anesthesia, and decompensation of preexisting strabismus is the most common presentation after topical anesthesia [1][2][3]. In this patient, the cataract surgery was performed under topical anesthesia. Therefore, the possibility of local anesthetic-induced myotoxicity was eliminated. In addition, no dysfunction of the superior or inferior rectus muscles was noted; instead, decreased activity of the superior oblique muscle and increased activity of the inferior oblique muscle were evident. Further, the results of a three-step test were positive, and facial asymmetry suggesting a long-standing superior oblique palsy was noted. Whether the superior oblique palsy was congenital or acquired can be determined by identifying the trochlear nerve on high-resolution MR imaging of the cranial nerves.

Morphometry of the Trochlear Nerve and Superior Oblique Muscle Volume in Congenital Superior Oblique Palsy

“…2,3 With congenital origin, associated findings are longstanding head tilt in old photographs, facial asymmetry, intermittent exotropia, amblyopia in the affected eye and atypical very-late onset diplopia. 4,5 Morphometric differences between the paretic and nonparetic superior oblique muscles (SO) in congenital SOP have been investigated using magnetic resonance imaging (MRI). [6][7][8][9][10][11] Recently, we were able to dichotomize SOP according to the presence or absence of the trochlear nerve and found clinical differences between these groups.…”

Imaging of Cranial Nerves III, IV, VI in Congenital Cranial Dysinnervation Disorders

“…A patient could develop diplopia after a phacoemulsification of cataract under topical anesthesia [21]. In such cases, the diagnosis of congenital CN IV palsy could be challenging, and MRI could be helpful for the correct diagnosis [22].…”

Surgical Outcomes of Inferior Oblique Myectomy in Unilateral Congenital Superior Oblique Palsy with or without Trochlear Nerve

“…In several aplastic cases, images were reformatted in the various oblique planes to fit the course of the trochlear nerve. [ 1 , 17 – 19 ]…”