Computerised tomography is an imaging method that uses rotating X-ray beams and computer processing to generate cross-sectional views of the body. In ophthalmology it is especially useful for bony structures and acute orbital pathology.
Technique
The scanner acquires multiple thin slices as the patient passes through the gantry, which are reconstructed into axial, coronal, and sagittal images. Intravenous contrast may be used to highlight vessels and soft tissues.
- Rapid acquisition, helpful in emergency settings
- Shows orbital walls, sinuses, and calcification clearly
- More sensitive than plain X-ray for fractures and foreign bodies
- Involves exposure to ionising radiation, so indications are considered carefully
Ophthalmic Uses
CT is often chosen for suspected orbital fractures, acute infections, calcified lesions, and metallic foreign bodies where MRI may be unsuitable. It also assists in planning orbital and sinus surgery.
- Reveals extent of trauma and relationship to vital structures
- Useful in differentiating cellulitis from abscess in orbital infections
- Can show enlargement of extraocular muscles in thyroid eye disease
- Findings complement MRI and clinical assessment
