Double vision arises from neurological deficit, muscle disease or due to distortion of orbital tissues.True binocular diplopia may be intermittent or constant, the images may be displaced horizontally, vertically or obliquely, and the diplopia may be worse in different positions of gaze. Thyroid orbitopathy and trauma are the commonest orbital cause of diplopia, although disease at the apex may cause multiple cranial nerve palsies. Anteriorly located tumours tend to displace the globe rather than cause diplopia.
Figure 10.1 Various forms of ocular displacement due to orbital disease: (a) axial proptosis associated with intraconal haemorrhage; (b) hypoglobus due to cholesterol granuloma of the frontal bone; (c) enophthalmos due to hemi-facial atrophy.
Although periorbital sensory changes, either paraesthesia or hypaesthesia, are uncommon, they provide a valuable guide to location of orbital disease. Sensory loss may occur with orbital inflammation or with malignant infiltration, particularly perineural spread from orbital or periorbital tumours. Specific enquiry should be made for these symptoms, as most patients will not volunteer them.
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