Utilization of Orbital Ultrasound and Optical Coherence Tomography in Papilledema and Pseudopapilledema patients
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Purpose: To evaluate the use of two non-invasive and low-cost tests, orbital ultrasound and optical coherence tomography (OCT), in differentiating papilledema (PE) from pseudopapilledema (PPE). Methods: Retrospective cross-sectional analysis included 51 patients referred to a neuro-ophthalmologist for presumed PE who were diagnosed with PE (n = 23, median Frisen scale II) or PPE (n = 28, 13 buried drusen and 15 obliquely inserted optic nerves) based on a thorough history, ocular/neurological exams and ancillary tests. Orbital ultrasound consisted of a B-scan to detect buried drusen and a standardized A-scan to measure optic nerve sheath diameter (ONSD). If ONSD at primary gaze exceeded normal limits (4.2 mm), a 30° test was performed to measure the ONSD at 30° lateral gaze. A Cirrus OCT Optic Disc Cube 200x200 scan was used to obtain the retinal nerve fiber layer thickness (RNFLT). Results: The mean ONSD (mm) at primary gaze was larger in PE (5.4 ± 0.6) than PPE (4.0 ± 0.3, p < 0.0001). The percent change in the ONSD at 30° gaze was greater in PE (22.4 ± 8.4) than PPE (2.8 ± 4.8, p < 0.0001). Average RNFLT (μm), was thicker in PE (219.1 ± 104.6) than PPE (102.4 ± 20.1, p< 0.0001). ONSD and 30° test had the greatest area under the ROC curve (AUC), 0.98 and 0.97, respectively; followed by inferior quadrant (0.90) and average RNFLT (0.87). In a subgroup of mild PE (Frisen scale I-II, n = 15), AUC remained high for ONSD (0.95) and 30° test (0.93) but decreased to 0.71 for average RNFLT. At 95% specificity, sensitivity (%) for ONSD, 30° test and average RNFLT was 91.3, 91.3 and 56.5, respectively for the entire PE group; 80.0, 86.7 and 13.3 for the mild PE subgroup. Conclusion: Orbital ultrasound and OCT are useful ancillary tests that can be done, along with a thorough examination, to effectively differentiate PE from PPE. Due to its easy access, RNFLT can potentially be used to detect moderate to severe PE. Ultrasound measurements may further assist eye care providers in differentiating mild PE from PPE when ophthalmoscopic findings are non-diagnostic.