Magnetic Resonance Imaging as a Potential Optic Nerve Area Measurement in Optic Nerve Atrophy Diagnosis

Objective: To report a threshold optic nerve area on magnetic resonance imaging (MRI) that predicts the clinical diagnosis of optic nerve atrophy in the population made by ophthalmologist. Those values could further clinically apply. Materials and Methods: The authors evaluated 23 clinical consistent patients with optic nerve atrophy. Among 46 patients’ eyes, 33 “affected” eyes were clinically diagnosed with optic nerve atrophy and 13 “unaffected” eyes were used for analyses. Twenty-three controls were also included, and their 46 eyes were used for analyses. Images from the coronal sequence on MRI, excluding the optic nerve sheath, at an image slice along the intraorbital portion of the optic nerve were used to measure optic nerve area. A freeform ROI measurement tool on the PACS was used to outline and measure the cross-sectional optic nerve areas. Results: There was a statistically significant difference in optic nerve area among patients’ eyes with optic nerve area (mean 1.35±0.41 mm²), patients’ unaffected eyes (mean 2.55±0.48 mm², p<0.001), and control eyes (mean 4.21±1.08 mm², p<0.001). In addition, a statistically significant difference in optic nerve area was observed between patients’ unaffected eyes and control eyes (p<0.001). Selecting a threshold MRI-measured optic nerve area was 2.7 mm² yielded a sensitivity of 100% and a specificity of 97.8% in predicting the presence of optic nerve atrophy by clinical diagnosis. Conclusion: The present study data suggests that MRI-measured optic nerve area of 2.7 mm² or less has both high sensitivity and high specificity for predicting the presence of optic nerve atrophy, making it a potential diagnostic tool for radiologists.