Severe strabismus after scleral buckling: Multiple mechanisms revealed by high-resolution magnetic resonance imaging

Abstract

Strabismus occurring after scleral buckling for retinal detachment typically is attributed to scarring, but this is not the only mechanism. We investigated use of magnetic resonance imaging (MRI) to identify a spectrum of mechanisms of strabismus occurring after scleral buckling. Prospective, noncomparative, observational case series in an academic referral setting. Six patients with long-standing, large-angle strabismus after monocular or binocular scleral buckling. Horizontal and vertical preoperative deviations, present from 8 to 120 months, ranged from 25 prism diopters to more than 90 prism diopters. Multipositional high-resolution MRI of both orbits was performed using surface coils in multiple, controlled gaze positions. Coronal, sagittal, and axial images were obtained as clinically appropriate. Different mechanisms of pathologic characteristics of the extraocular muscles (EOMs) in complicated strabismus after scleral buckling. Magnetic resonance imaging readily demonstrated EOM size and contractility, as well as features of scleral buckle hardware such as grooves and junctions and relationships of EOMs to the buckle and sclera. Imaging demonstrated that 5 rectus EOMs were disinserted from the globe at the buckle: 2 superior rectus, 2 medial rectus, and 1 lateral rectus. One patient with suspected inferior rectus muscle disinsertion had restrictive strabismus as a result of interference by a meridional explant and myopic staphyloma. Magnetic resonance imaging demonstrated anterior migration and transection by the silicone element through rectus EOMs in 3 patients. Disinserted EOMs were retrieved successfully by transconjunctival surgery in 4 patients and by orbitotomy in 1 patient, markedly improving alignment even as long as 5 years after EOM disinsertion. Multipositional high-resolution MRI provides valuable information such as location and contractile potential of disinserted EOMs, as well as mass effect from the scleral buckle. Preoperative orbital MRI may be a useful tool to distinguish multiple mechanisms of persistent severe strabismus after scleral buckling and is helpful in surgical planning.