Radiographic Measurement of Normal Optic Nerve and Optic Nerve Sheath Diameters Using Different Modalities

Abstract

We aimed to review the role of different types of imaging (computed tomography [СТ], ultrasonography [US], magnetic resonance imaging [MRI]) in measuring the optic nerve diameter (OND) and optic nerve sheath diameter (ONSD) in adults and the potential advantages and limitations of each modality. A literature search was carried out using ResearchGate, Saudi Digital Library, Google Scholar, and Mendeley databases between 2010 and 2021 (papers presented in English) with the keywords “computed tomography,” “magnetic resonance imaging,” “ultrasonography,” “optic nerve sheath diameter,” and “optic nerve diameter.” Of the 60 articles analyzed, 42 were included in the review. Compared to ONSD, the evidence for OND appeared to be more limited. After comparing all three imaging modalities (CT, MRI, and US), we concluded that for the most accurate measurements of ONSD we should be using MRI (range: 4.0–6.0 mm). CT (range: 4.4–6.7 mm) would provide the second most exact measurements after MRI. Although CT and MRI provide the most consistent and accurate measurements, ultrasound is more commonly used (ONSD range: 3.4–7.7 mm) due to it’s being non-invasive, easy to use, and easily available anywhere, from big hospitals to small clinics, unlike CT and MRI. All three imaging modalities can provide good measurements, and hopefully, soon ultrasound will be as accurate as MRI in measuring the optic nerve.