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Saumya Mihir Shah, Khin Kilgore, Christopher Hunt, Erick Bothun, Cheryl Khanna; Orbital Anatomy Magnetic Resonance Imaging in Diplopic vs Non-Diplopic Patients after Glaucoma Drainage Device Placement. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3939.
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With increased utilization of glaucoma drainage devices (GDD) for glaucoma management, new-onset persistent diplopia has become a common complication of GDD placement. Understanding orbital anatomy in patients with diplopia after GDD placement may provide information regarding risk of diplopia and post-operative management. The purpose of this study was to examine the orbital anatomic differences in diplopic and non-diplopic patients after GDD implantation using orbital magnetic resonance imaging (MRI).
Seven eyes (N=4 with diplopia and N=3 without diplopia after GDD placement) of 7 patients with placement of Baerveldt 250 (B250), Baerveldt 350 (B350), or Ahmed FP7 (FP7) GDD in the superotemporal quadrant were prospectively enrolled. Exclusion criteria included multiple prior GDD and scleral buckle placement, or inability to complete the Diplopia Questionaire (DQ). All patients underwent a 3.0T orbital MRI evaluation with 3D volumetric T1 and T2 weighted sequence. Images were analyzed by a neuroradiologist for orbital volume, axial length, orbital distances, presence of superior rectus-lateral rectus (SR-LR) band, position of GDD, and angle between the SR and LR muscles (SR-LR displacement and quadrantic angle).
Non-diplopic patients had a higher average orbital axial volume compared to diplopic patients (931.7 mm2 v. 911.5 mm2). Both non-diplopic and diplopic patients had similar average orbital coronal volumes of 11.8 cm2 and 11.6 cm2, respectively. Average orbital rim anterior and posterior distances were larger in diplopic patients. The average SR-LR displacement angle was larger in diplopic patients than non-diplopic patients (101.6 v. 94.7). However, the average SR-LR quadrantic angle was larger in non-diplopic patients (89.1 v. 86.6). The SR-LR band was present and intact in all patients post-operatively. GDD placement was between and under SR and LR for B350 patients, and between SR and LR for B250 and FP7 patients.
The decreased orbital axial volumes and increased orbital rim distances in diplopic patients suggests the need for further studies to understand the role of orbital anatomy in occurrence of diplopia. Static MRI imaging was not helpful in identifying differences in inherent orbital characteristics that reveal an etiology of diplopia in patients with GDD implantation. GDD malpositioning was not seen on MRI in any patient.
This is a 2020 ARVO Annual Meeting abstract.
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