The technique is limited by lengthy scanning time, increased cost compared to CT, and requirements for sedation in children and other non-compliant patient groups. High-resolution MRI facilitates evaluation of chorioretinal detachments and potential underlying neoplasms. Table 1 shows the common MRI characteristics of the various structures in the globe. Dedicated orbital MRI scans (1.5 or 3 tesla platforms) are performed in our institution using the following protocol axial and coronal T1-weighted (T1W) with and without fat suppression, axial and coronal short tau inversion recovery (STIR) or fat suppressed T2-weighted (T2W) and multiplanar fat-suppressed gadolinium-enhanced T1W images. MRI provides exquisite soft tissue contrast and the sclera can be distinguished from the choroid and retina.
CT is also useful for evaluation of globe calcifications, especially in the case of retinoblastoma ( 1). CT is the technique of choice for evaluating metallic or paramagnetic foreign bodies, whereas MRI is contraindicated due to potential migration and local heating. Non-contrast CT is useful in the initial evaluation of orbital and globe trauma for the assessment of fractures, extra-ocular muscle herniation and suspected globe rupture.
Recent advances in MR and CT technology that allows for detailed visualisation of the globe has resulted in frequent, incidental detection of abnormalities. Majority of eye globe imaging is performed secondary to CT and MRI imaging of the brain for various reasons ranging from trauma to neoplasia.
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