Emergency! Double Vision!
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Double, double toil and trouble;
Fire burn and caldron bubble.
Cool it with a baboon's blood,
Then the charm is firm and good.
Macbeth: IV.i 10-19; 38
Specialists in ocular misalignment (“strabismologists”) often see patients with double vision (diplopia). Sometimes the symptom is minor and infrequent, sometimes frequent and even disabling. But how often is diplopia an emergency?
Researchers at the University of Miami reviewed the records of 350 patients who presented from 2014-2019 with a complaint of diplopia on an emergency basis (JAAPOS 2021;25:175-6). Most of these patients were adults, which is not surprising, partly because children tend either not to have double vision (because their brains suppress the second image) or they just don’t complain about it to their parents.
Almost 8% of the patients in this study had monocular diplopia, meaning that their double vision was caused by distortion or other abnormalities in just one eye, rather than misalignment of the two eyes. Of the patients with binocular (strabismic) diplopia, about half had horizontal misalignment, about a quarter had vertical misalignment, and the remainder had combined horizontal/vertical or torsional diplopia.
The majority of these patients had acute cranial nerve palsies, affecting most frequently the abducens nerve (CN VI 47%), followed by the oculomotor nerve (CN III, 30), trochlear nerve (CN IV 22%), or multiple cranial nerves (1%). Brain imaging was performed in 205 patients, and was unremarkable in just over 50% of cases. Abnormalities discovered on brain scans included strokes (25 patients), brain tumors and other masses (25), orbital lesions (20), multiple sclerosis lesions (14) and elevated intracranial pressure (10).
The authors concluded that immediate neuroimaging should be strongly considered for patients presenting with diplopia and no obvious explanation.
I was surprised at how many oculomotor nerve (CN III) palsies were found in the study relative to abducens and trochlear nerve palsies. In my experience CN III palsies are much less common; trochlear palsies are particularly common after head injuries / motor vehicle accidents. Perhaps this discrepancy is due to the older population studied in this publication cohort or because University of Miami is a tertiary care facility, more likely to attract patients with unusual or more difficult problems (like CN III palsy).
Fortunately, many cranial palsies improve over time; for those patients with persistent diplopia, there are both nonsurgical and surgical options for relieving symptoms. So one need not resort to the ingredients prescribed by Shakespeare’s witches:
Eye of newt and toe of frog,
Wool of bat and tongue of dog,
Adder's fork and blind-worm's sting,
Lizard's leg and howlet's wing,
For a charm of powerful trouble,
Like a hell-broth boil and bubble
Benjamin H. Ticho, MD