Ophthalmology – Diplopia: By Martin ten Hove M.D.

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Ophthalmology – Diplopia
Whiteboard Animation Transcript
with Martin ten Hove, MD
https://medskl.com/Module/Index/diplopia

Diplopia or double vision is something that you must take very seriously because it can be caused by an intracranial aneurysm or an intracranial mass.

When I examine a patient with diplopia there are two signs that make me very concerned:

A dilated pupil; and
Other cranial nerve involvement.

The 3rd cranial nerve innervates the superior, inferior, and medial recti, as well as the inferior oblique, the levator palpebrae, and the iris constrictor. A complete palsy of the 3rd nerve usually causes both horizontal and vertical diplopia, ptosis, and mydriasis.Of most importance, however, is the status of the pupil in a 3rd nerve palsy.

A spared pupil (i.e. normal function of the iris constrictor), in the setting of a complete 3rd nerve palsy, suggests that the etiology is ischemia due to diabetes or hypertension. These can be typically can be followed expectantly for a full recovery in 6-12 weeks.

A dilated or “blown” pupil, on the other hand, indicates a compressive lesion – in the most worrisome case – a fatal cerebral aneurysm.

This why it is essential to recognize the clinical signs of a 3rd nerve paresis and if the pupil is blown, a CT angiography must be immediately obtained to rule out a life threatening aneurysm.The second critical step to do in any patient with diplopia is examine other cranial nerves. Tumors in the posterior fossa or in the cavernous sinus may cause abnormal function of the 3rd, 4th, and/or 6th cranial nerves as well as any of the other cranial nerves and tracts descending to the spinal cord.The best clinical approach is to use the clinical findings to localize the area of pathology and use an appropriate mode of neuro-imaging to investigate the structures in the area.